Amber Book - PPD

Question 1

Think of every large piece of outdoor equipment you might need for a large building and decide where it should go on a site.

Answer 1

Dumpster: out of view, far from noses (smells bad), not near quiet-room windows (banging lids)

Transformer: between the municipal service (electrical wires on poles or electrical wires underground) and in-building switch gear. Could be on pole, on the ground near the building 4′ from the road, underground outside building or inside building. Ugly and sometimes buzzes, so out of view if possible. If inside building often non-flammable coolant needed inside the transformer.

Cooling tower: These are large. They want to be out of view and they need access to the atmosphere so they can’t be indoors. They are often near the chillers they serve, but they can be remote if needed.

Generator: loud, but if it is a backup generator, it will be rarely used and the noise will not be a problem. Must exhaust to outside, so typically a generator sits outside the building. If it is an indoor generator, it must exhaust to the outside.

Question 2

When given a chance, how you decide what is the least expensive construction technique?

Answer 2

What you see most often on construction sites is usually the least expensive option.

OSB sheathing is more common, and less expensive, than plywood sheathing

Plywood is more common as formwork, and less expensive, than insulated concrete forms (ICFs)

Vinyl siding is more common, and less expensive, than wood siding

Asphalt roadway is more common, and less expensive, than concrete roadway

And so on. . .

Question 3

What is a right-hand reverse-bevel door?

Answer 3

See image

Question 4

How can we shade windows?

Answer 4

South facing: deciduous trees, horizontal louvers, light shelves, shade with other adjacent building masses

East- and west-facing: deciduous trees, vertical louvers, light shelves, shade with other adjacent building masses

North-facing: shading not required

Question 5

Shading lower southern sun requires longer horizontal overhangs

Answer 5

Shading lower southern sun requires longer horizontal overhangs

Question 6

Shading higher southern sun requires _______ (shorter or longer?) horizontal overhangs.

Answer 6

Shading higher southern sun requires shorter horizontal overhangs

Question 7

Position the vertical louvers on the east or west face so that the “cut-off” angle of each fin shades direct sun.

Answer 7

The geometry of the fins vary relative to the position of the sun (see the next card)

Question 8

Position the vertical louvers on the east or west face so that the “cut-off” angle of each fin shades direct sun.

Answer 8

This geometry will vary based on the specific location of the sun (see the previous flash card)

Question 9

Design a light shelf. Draw it in section. Try to get the proportions and materials correct.

Answer 9

A: height of light shelf should be such that it shades room occupants from sky view

B: height of top light should be as high as possible (with “A” in mind)

C: extension of light shelf should be 1.4 times b if light shelf faces due south (1.7 times b if light shelf faces more than 20 degrees to the east or west of south). Figure out why that would be? (answer below). In hot climates the extension of the light shelf can be louvers to allow built-up heat to escape upward.

x: to get light deep into the room (and therefore mitigate glare) sunlight should reflect off top of light shelf and then off light-colored ceiling

R: because view to the sky is shaded, areas close to the window have less glare

z: top of light shelf should be painted white. In cold climates, the top surface can be mirrored. Figure out why climate matters (answer below). Bottom of light shelf should also be light colored so that it doesn’t contrast too heavily with the bright outdoors when viewed from within.

Answer 1: the sun is lower in the sky in the east and west than in the south, especially near sunrise and sunset. To shade from the sun, we need to extend the light shelf outward farther.

Answer 2: in a hot or mixed climate, a mirrored top surface would reflect unwanted heat into the occupied space.

Question 10

What is the difference between passive and active radon mitigation?

Answer 10

Passive system: Caulk/sealant in foundation cracks and where the slab meets the foundation wall, and plastic sheet below the slab seals the building from the radon in the ground. Continuous, airtight plastic pipe extends from the sub-slab gravel straight up through the roof to allow an easy path for underground radon to escape without entering the house. No fan needed.

Active radon mitigation: fan pulls air (and radon) through a continuous plastic pipe from below slab or crawlspace to the atmosphere, bypassing the building. We don’t want the radon that is pulled out of the foundation to leak back into the building, so we seal the slab; we put the fan in the attic or anywhere else outside the the enclosure; and we discharge the radon from the pipe at least 10 feet from a window, door, or other opening (including doors and openings in adjacent buildings), at least 10 feet off the ground, and above the roofline, as close to the ridge as possible. Angle the pipe discharge away from any bulding surface to avoid moisture discharge or mildew build up on the building wall or roof.

For new homes, a passive radon system should be installed (it’s cheap, and if it needs to be converted into an active system later because of high radon levels, simply add an inline fan to the existing passive pipe in the attic). In areas of the country with high radon levels, new homes should have an active system installed from the beginning.

Question 11

When the shear wall is overly-perforated with apertures or doesn’t continue uninterrupted all the way from roof to foundation:

Answer 11

When the shear wall is overly-perforated with apertures or doesn’t continue uninterrupted all the way from roof to foundation:

Question 12

What is the “soft story” problem?

Answer 12

See Image

Question 13

What is the problem with the “soft story” problem?

Answer 13

See image

Question 14

There are urbanistic and programmatic reasons why you might want to design a tall or flexible or otherwise different first floor. What is the “soft story” solution?

Answer 14

High first floors with slender columns doesn’t always bring about a soft story first floor. The problem arises when the columns are the primary resistors of lateral force.

Question 15

Calculating code stair width

Answer 15

You calculate the stair width–for the whole stair system–based upon the floor with the highest occupancy load. That floor’s width controls all the way up and down the exit stairs, so you don’t have to add cumulatively. For stairs serving one floor and fewer than 50 occupants, the minimum width is 36″. For stairs serving multiple floors, the no-matter-what minimum width (always measured between handrails) is 44″. To calculate the minimum width for your building, you’ll take the floor with the highest occupancy and multiply that occupancy by 0.3 (multiply by 0.2 if sprinklered and not a fireworks factory or prison, but I’m going to use 0.3 going forward for simplicity). After you multiply the highest-occupancy floor’s number of people by 0.3, that will give you a minimum TOTAL width, inclusive of all your exit stairs. You’ll split that total up between the total number of exits required for your building:

Occupant Load per Story: 1 to 500 people: 2 stairs; 501 to 1000: 3 stairs; more than 1,000: 4 stairs

So if you have 100 people per story and four stories, you will need two exits, minimum. You’ll multiply 100*0.3 to get a minimum TOTAL stair width of 30″, divided across two exits, which returns you 15″ per stair. But, there is a minimum stair width of 44″ so each stair will be a minimum of 44″

If instead you have 600 people on your third story and 100 per floor on the other levels, you’ll take 600 * 0.3, which returns you 180 inches and minimum number of three exits, so 60″ per exit stair and three exit stairwells.

Only stair widths within 30″ of a railing “count” as egress, so were the width of the example above more than 60″ wide, we’d need an intermediate rail in the middle of the stairs (or more likely, add a fourth stair). An intermediate stair rail looks something like this. https://i.pinimg.com/originals/09/82/64/098264fef1ba1a445aafa7f39cc395d4.gif

There are exceptions for refrigeration rooms and daycares and all kinds of different rules such that you should never use my generalizations in lieu of your own code search when designing your buildings. This is just provided as a general rule-of-thumb, useful for studying, but not verified and never appropriate to replace your own code search.

Question 16

Shear (pin) vs Moment Connections

Answer 16

Straighten out your arm and hold it horizontally. Now use your hand to grab the shoulder of a loved-one who is standing nearby. If that loved-one suddenly moves out of reach, does your arm fall or does it remain horizontal? If it falls, your shoulder was a shear (or pin) connection. If it still remains outstretched horizontally after your loved-one moved—if it remains cantilevered from your body—your shoulder was in a moment connection.

In steel, you can recognize a shear connection because (generally) the beam web is bolted or welded to the column, but the beam’s flanges are not. Shear connections resist gravity, but don’t do well in the presence of lateral forces like wind and seismic. They therefore need additional lateral resistance from cross bracing or a shear wall (rigid lateral membrane) so that a hurricane doesn’t push over the pin-connected structure. The nomenclature can be confusing: shear connections need a shear wall (or cross-bracing) to resist lateral forces. Importantly, shear walls or cross-bracing are not required everywhere—only in a few of the structural bays.

By contrast steel moment connections (generally) bolt/weld both the flanges and web to the column and resist both vertical gravity and lateral wind/seismic. They can handle the hurricane without the benefit of shear walls or cross-bracing. The additional cost of attaching the flanges doesn’t feel like it would amount to that much extra in a building’s budget, at least not relative to the extra cost of cross-bracing or building a concrete shear wall. But given the skill-level of the structural steel trades, and their location high atop steel structures exposed to the elements, the extra cost of moment connections (bolting the flanges to the beam) is surprisingly significant. Plus, code life safety requirements often dictate a concrete stair tower that can “do double-duty” as the shear walls without extra cost. So most of the connections you see in the field when a steel beam meets a steel column are shear connections. . . which means that if the neighboring column were to jump out of the way, and there was no shear wall in the bay and no cross bracing in the bay, the beam would pivot downward.

If the stair tower is constructed of concrete (or concrete block with enough reinforcing bar), it can double as the shear walls for the building, resisting lateral wind and seismic loads and allowing the steel connections to be shear (pin) type.

Still unsure? You can think of a moment connection like this image, one where the beam won’t swing like a hinge on the column if the second column supporting the beam suddenly disappeared..

This mushroom column too:

Question 17

If our goal is to shade the windows, which illustrates the west side of the building?

Answer 17

Vertical fins shade the east and west elevations, horizontal fins shade the south, no shading needed on the north

Question 18

Sketch a convective loop inside a wall cavity

Answer 18

In wall cavities of widths greater than 4in, a convective loop forms as air naturally rises up the warm side of the cavity and falls along the cold side. This acts as a short circuit of the thermal barrier, accelerates the transfer of heat from inside to outside, and cancels (or even reverses) the thermal benefit of the cavity. This is especially acute in tall cavities in cold climates.

Note the role of radiant heat exchange across the cavity, as the warm side “sees” the cold side and transfers its heat by electromagnetic energy.

Note also the role of conductive heat exchange across the solid elements of the wall

The physics of a cavity wall suggest conduction, radiation, and convection are all going on simultaneously—but for simplicity, we typically measure heat transfer through the wall in equivalent conduction terms (R-value).

Question 19

Conduction, convection, and radiation across a wall assembly

Answer 19

See image

Question 20

Sketch convective loops as they develop in roof and floor assemblies

Answer 20

See image

Question 21

Are wind loads higher at the top of tall buildings?

Answer 21

Yes, wind speeds increase with the height above the ground (but gustiness—circulation of wind in eddies—decreases with height).

Wind is notoriously difficult to account for in tall buildings. The high pressure (windward) side takes on a “pushing” lateral load, while the low-pressure (leeward) side takes on a suction pulling load in the same direction. This can cause the building to “gallup,” vibrate, and sway in ways that prove unnerving for occupants in higher floors. The downwind pattern formed by the building’s disruption of wind flow, called “vortex shedding,” can create a force perpendicular to the wind direction and dislodge windows. To limit the structural impact of winds on a tower, soften the corners in plan (rounded or chamfered, rather than right angles), taper or set back the building plan as it rises, twist the building as it rises, provide large apertures in the building’s windward face that allow the wind to pass through at some floors, or position a heavy damper in a top floor to counteract the natural vibration of the building. See this digital model. Most of these strategies will also reduce the canyon effect wind speed on the city streets below as well. For more, go here.

Question 22

Read the following AIA contracts. (It is probably not an efficient use of your study time to memorize them unless doing so will also help you day-to-day at work.)

Answer 22

Owner-Architect Agreement B101 is here (most important one to know)

Owner-Contractor Agreement A101 is here

General Conditions of the Contract for Construction A201 is here

Architect-Consultant Agreement C401 is here

*As with so much of the other content in this division, these are also important for CE, PjM, and PcM exam divisions, and to a lesser extent, PA and PDD. That is why you’ll save yourself time–both in total hours of studying and in total time until licensure–if you treat all six divisions as one long six-part exam to be taken in one or two weeks. I know you are scared of this idea, but I’m certain I’m right about this.

Question 23

In which condition does an exit (stair) need to be pressurized to keep smoke out?

Buildings made of combustible construction types (wood (Type V) construction)

or

Underground buildings

Answer 23

Underground buildings have stairs that must be pressurized.

The egress path (the path for getting out in an emergency) has three parts,

1. Exit access (for simplicity, think of that as the corridor from the room to the stairs)
2. Exit (the stairs)
3. Exit discharge (door from the stairs to outside)

We want occupants to be safe—or at least safer and more protected from fire and smoke–when they reach the exit (stair), even if they are not yet out of the building. One of the ways we do that, is to pressurize the stair with a giant fan at the top that is activated by the building’s smoke detector. With the stair pressurized, smoke is less likely to fill the stair. This type of system is required in the following building categories:

1. In tall buildings-–it takes a long time to walk down 100 floors, especially if others are joining you at each floor and clogging things up, and we need you not to choke from smoke inhalation on the way down. . . We pressurize the stair so it doesn’t fill with smoke.
2. In underground buildings—you need to move up to make your way outside safely, but smoke rises, so we don’t want you moving up to a too-smoky-to-breathe higher floor. . . We pressurize the stair so it doesn’t fill with smoke.

You can see an example of such a pressurization fan by looking up the next time you are in a stairway of an underground building or tall building. It looks like this. The diagram of it looks like this.

Question 24

How do we best reduce the build-up of low-frequency sound in a room (for instance, rumble from mechanical equipment)?

Specify materials with a low Noise Reduction Coefficient (NRC)

or

Position sound-absorbing materials near the corners and edges of walls

Answer 24

A: Position sound-absorbing materials near the corners and edges of walls. We call this a “bass trap.”

Low frequency sound energy–low tones from mechanical equipment like fans, transportation noise like trucks, and amplified sound like in da club—naturally build up around the perimeter and corners of a room. Sound-absorbing materials positioned near the corners and edges of walls absorbs more of that build-up. For more, see my book, Architectural Acoustics Illustrated.

Question 25

Which type of soil is more stable to build on?

Clay

or

Sand

Answer 25

Answer: Sand

Clay behaves unpredictably when it gets wet. It swells.

Of course most soil boring reports detail a mix of sand and clay (and silt and gravel). It is then the proportion of clay that will determine stable soil.

Question 26

A good barrier for preventing sound from transmitting from one room to the other is _______.

Absorptive

Or

Airtight

Answer 26

Answer: Airtight

Assemblies that are massive, airtight, and structurally discontinuous do the best job keeping out the neighbor’s TV noise, or keeping out the bus noise, from your apartment. By contrast, sound absorption is used to reduce the sound buildup inside the same room where the sound is made, and has less impact on the neighbor’s noise.

In the same way that cloud cover, temperature and wind speed are each measures of weather, but not very related to one another . . . room acoustics (sound absorption), noise control (sound isolation), and impact noise control (from footfall) are each measures of acoustics but not very related to one another. A room with high or low quantities of absorption may or may not be good at keeping sound from the adjacent room out, just as a cloudy day may or may not also be windy.

Question 27

A larger room has a _______ reverberation time than a smaller room.

Longer

or

Shorter

Answer 27

Answer: Longer

Large rooms, rooms with fewer surfaces, and rooms with harder, smoother, less-fuzzy surfaces are more reverberant (sound lingers longer after it is suddenly stopped). The more reverberant the room, the longer the reverberation time, measured in seconds. Rooms with unamplified speech, amplified speech, and amplified music generally want to be less reverberant: they want to be smaller, with fuzzier surfaces. In contrast, rooms for unamplified music, like concert halls, generally want to be more reverberant: larger, with harder and smoother surfaces.

Question 28

A surface with an absorption coefficient of 1.00 is considered _______.

Sound-reflective

or

Sound-absorptive

Answer 28

Answer: Sound-absorptive.

Sound absorption coefficient measured for the surface of a building material (⍺), ranges from 0.0 (fully sound reflective) to 1.0 (fully sound absorptive). Most sound absorbing materials have ⍺ values greater than 0.5 and most sound-reflecting materials have ⍺ values less than 0.2

Question 29

What is an overturning moment

Answer 29

For the curious or confused, see here for a more detailed calculation (probably not worth memorizing but may be interesting to you).

Question 30

A shed has a wind load of 1.0 kips and a gravity load of 2.0 kips. Using the free body diagram, calculate the magnitude and angle of the resultant force.

Answer 30

Answer: 2.2 Kips at 63° from horizontal

http://flashcards.amber-book.com/wp-content/uploads/2020/05/Freebody-Diagram-1.mp4

Question 31

It’s wintertime, it’s been a rainy month, and there’s moisture inside the parapet structure. The building includes an arboretum. This can most likely be best addressed with _______.

Insulation

Rain barrier

Vapor barrier

Ventilation

Answer 31

Answer: insulation

For more explanation, visit this video.

Question 32

How many lavatories, water closets for boys, water closets for girls, and water fountains are required for a middle school with an occupancy load of 1000 people? Use the internet liberally.

Answer 32

You’ll want to visit the IBC here to check with Table 2902.1. On the exam, this will be provided in the question, or more likely, in the case study material.

Lavatories: 20 (1 per 50 occupants)

Water closets for boys: 10 (1 per 50 occupants)

Water closets for girls: 10 (1 per 50 occupants)

Water fountains: 10 (1 per 100 occupants)

With few exceptions, you must assume that 50% of occupants are women and 50% are men, so 500 of each for this example. Here we assume Educational (E) occupancy type.
Remember that a “water closet” is a toilet and a “lavatory” is a sink without food waste going down the drain. This can be confusing because in common language, sometimes a bathroom is called a water closet, or a bathroom is called a lavatory.
For mixed-use buildings, calculate the number required for each occupancy classification (E, A, S, etc.) and then add them together.
Include the occupancy load for outdoor dining and entertainment spaces (courtyards, beer gardens, terraces)

Question 33

The following diagram depicts a building plumbing system. The blue arrow points to a pipe that brings hot water back to the hot water heater from the rooms with fixtures (not hot wastewater, but hot potable water). Why would we want to return hot water to the hot water heater?

It’s more efficient (less heat loss through pipes)

It’s safer (less likely to scald children or others not able to effectively work the fixture controls)

It creates less stress on the water pumps

Water in fixtures gets warm more quickly

Answer 33

Answer: Water in fixtures gets warm more quickly

Hot water circulates, especially in large buildings, to keep warm water in the pipes adjacent to fixtures so occupants don’t have to wait for the column of hot water to make it all the way from the hot water heater to a distant fixture. This arrow points to a hot water return pipe that brings hot water back to the basement where it is reheated and recirculated, even when no one is running a fixture in the building. In this case, the circulation is maintained (slowly) by natural convection as the hottest water rises and not-as-hot water sinks in the pipes. In some buildings, hot water circulation is instead maintained by an electric pump.

Question 34

How many amps for a 2160 watt bedroom circuit in a single-family detached house? Ignore power factor. Given W=I*V

Answer 34

Answer: 18amps

Standard voltage is 120 volts.

Question 35

The current calculation in the previous problem can be used to _______.

Locate the breaker box

Locate the underground power utility

Reduce the amount of power used (for energy conservation)

Size the wire

Answer 35

Answer: Size the wire

Question 36

Last month I volunteered to help out with the renovation of a building on campus where people assemble for banquets and weddings. The operators of the space field regular complaints of excessive reverberance: for instance, at a banquet a dean is recognizing faculty who have won teaching awards, and each syllable of the dean’s speech seems to linger in the air too long, interfering with the next syllable before it is uttered. How much extra sound absorbing material, in square feet, should be added to move this room to a (1000 Hz) reverberation time of 0.40 seconds for improved speech intelligibility?

Given:

I measured the existing reverberation time to be 0.73 seconds at 1000Hz

The sound absorption coefficient (SAC or ⍺) of the absorbing material they chose, measured at 1000Hz, is 0.95

I measured the total surface area of all the surfaces in the room to be 4365 sf

I measured the total volume of the room to be 11619 cu ft

Assume that the absorbing material will replace gypsum board with a sound absorption coefficient (SAC or ⍺) of 0.04

You can see photos of the space here and here.

As always, I may have given you more information here than you would need to solve this (or may not have).

Answer 36

Answer: Add approximately 730 sf of absorbing material

https://flashcards.amber-book.com/wp-content/uploads/2020/10/ReverbTime.mp4

Question 37

How many footcandles would be measured 3’ above the floor directly below a fixture hung at a height 9’ above the floor

Given:

a point source light

9,000 candle power (cp)

Ignore reflectance from room surfaces, dirt depreciation, etc.

Answer 37

Answer: 250 fc

The US lighting industry has far too many metrics to easily keep track of.

Measures of how much light is coming out of a lamp

Candle power (CP): measure of how much light is coming out of a lamp. A 100,000 candlepower spotlight is equal to the light of 100,000 candles. Because it is an imperial measurement, it is easily converted to footcandles, which is also an imperial measurement.

Candela: A more scientific measure of candlepower. For our purposes, we can use the two terms interchangeably, though the historical “candlepower” unit is equal to 0.981 candelas.

Lumens: metric version of the same thing. 1 candela = 13 lumens. “Lumens” is the most common metric used in the industry, but is a bit less intuitive when converting to footcandles and a bit more intuitive when converting to lux (the metric version of how much light is hitting a surface).

Measures of how much light is striking a point in a room

Footcandles: how much light arrives at a point on a surface (imperial)

Lux: same as footcandles, but metric. 1 footcandle is equivalent to approximately 10 lux. You don’t need to memorize conversion rates

http://flashcards.amber-book.com/wp-content/uploads/2020/07/Illumination-directly-downward.mp4

Question 38

“Horizontal footcandles” is a measure of light arriving from ______.

Above

or

The side

Answer 38

Answer: Above!

Horizontal footcandles is a measure of light impinging upon a horizontal surface: as if you put the light meter flat on a table, so it measures light arriving from above.

Vertical footcandles measures light impinging on a vertical surface. . . so light arriving from the side.

This is a bit counter-intuitive until you know the backstory.

Question 39

How many horizontal footcandles would be measured on a table 3’ above the floor on a desk surface. The fixture is hung at a height 9’ above the floor, and in plan, the desk is 5’ to the right of the fixture.

Given:

An omnidirectional point source light

9,000 candle power (cp)

Answer 39

Answer: 113fc

http://flashcards.amber-book.com/wp-content/uploads/2020/07/Horizontal-footcandles.mp4

Question 40

How many vertical footcandles would be measured at a point on a wall 3’ above the floor. The fixture is hung at a height 9’ above the floor, and in plan, the wall is 5’ to the right of the fixture.

Given:

An omnidirectional point-source light

9,000 candle power (cp)

Answer 40

Answer: 95 fc

Calculate the angle Θ

SOH CAH TOA

tan(Θ)= ⅚

tan-1(⅚)=Θ or arctan(⅚)=Θ. . . .

Θ =40 degrees

Calculate the distance D

Pythagorean theorem

52+62=D2

D=61

Calculate the vertical footcandles

Question 41

How many horizontal footcandles would be measured on a table 3’ above the floor on a desk surface. The fixture is hung at a height 9’ above the floor, and in plan, the desk is 5’ to the right of the fixture.

Given:

a fixture with the following photometric curve

Answer 41

Answer: 85 horizontal footcandles

Question 42

Vierendeel Truss

Answer 42

Truss without triangles–only right angles. Useful if you don’t want angled truss components to interfere with windows, but for it to function as a truss, the connections at the top and bottom chords have to resist moment forces and are often beefy and expensive. They look like this.

Herzog and deMeuron’s Jenga building in New York achieves its cantilevers with two-story concrete Vierendeel trusses. You can see them on this short time-lapse construction video.

Question 43

How do we route power to desks that are far from a wall when the floor is concrete?

Answer 43

https://flashcards.amber-book.com/wp-content/uploads/2020/10/Raceways.mp4

Question 44

How do we bury conduit into concrete structure?

Answer 44

We can run steel conduit inside concrete slabs. They are placed in the bottom half of the slab (in section) to help with tension the way that rebar runs in the bottom portion of spanning horizontal concrete. The top of the conduit sits below at least ¾ inch of concrete covering and parallel conduit runs must be spaced, O.C., a distance at least three times the larger conduit outside diameter. Conduits cross at right angles. See here for an example (some of these conduit look to be closer together than allowed).

We can also pour a non-structural concrete topping over the structural slab and nestle the conduit into the topping.

Question 45

Underfloor raceway ducts

Answer 45

They’re called “ducts” in this context, but they carry electrical and data wires rather than air. They can sit beneath, or flush to, the floor. Expensive, disruptive, and not very popular anymore in favor of moving power in the ceiling below, under-carpet, or cellular metal floor raceways. See here for an example of ducts for raceways.

Question 46

Floor cellular raceway systems

Answer 46

Floor cellular raceways provide both the metal part of a concrete slab’s structure, the floor pan, formwork, and the wire management in a single proprietary product. See this excellent video (the link starts the video midway through because that is the best place to start).

Question 47

Poke-through floor boxes vs floor cellular raceways

Answer 47

Poke-through floor boxes: Best for retrofits and renovations because the floor slab is already poured. The fifth floor open-office wiring is run under the floor slab, in the ceiling of the fourth floor. Then holes are bored for poke-through floor boxes with electrical receptacles and data jacks for the mid-floor desk. Click here to see what poke-through fixures look like.

Floor cellular raceways: Best for new construction. The fifth floor slab is poured with a floor cellular raceway system integrated into it. If you forgot what these look like from the last flash card, click here.

Question 48

Under-carpet wiring system

Answer 48

Under-carpet wiring systems: imagine laying something that looks like tape, but is actually flat insulated electrical conductors aligned edge to edge. Only 0.03 inches thick, so you can’t feel it under the carpet when you walk on it. Obviously the least expensive solution and obviously the one with the least impact on floor-to-floor heights. Doesn’t work as well for large, complicated floors because with higher power needs comes the need for thick electrical boxes that can’t lay flat under your carpet. See this video at this timestamp (you don’t need to watch all of it and you are encouraged to watch it at 2x speed).

Question 49

Surface metal raceways

Answer 49

You’ve seen surface metal raceways on walls (they often have a metal back but a visible plastic–not metal–cover). They can be mounted on floors too. Don’t specify these on floors unless you like to trip your occupants and want to ensure floors aren’t cleaned properly. They are only specified when sufficiently out-of-the-way of everyday foot traffic. See here.

Question 50

Ceiling raceways

Answer 50

Ceiling raceways, also sold as proprietary systems called “manufactured wiring systems”: run the power to the third floor open-plan desk through the ceiling of the second floor below it. Then install a poke-through fixture. Expensive because of all the drilling through the floor, and in retrofits, this might inconvenience the office tennant, below, but is a smart out-of-sight solution if you didn’t install a floor cellular raceway when the building was constructed, don’t like carpet, and hate the hollow thump of raised access flooring

Question 51

Raised access flooring system

Answer 51

Raised access flooring systems float floor tiles on pedestals over a 12in to 24in hollow cavity. Conduit (and ducts) can then be flexibly run–and later adjusted–under the floated floor with relative ease. Obviously raised access floors increases the required floor-to-floor height. See here.

Question 52

Floor-to-ceiling raceway poles

Answer 52

See here for an example of a Floor-to-ceiling electrical/communication raceway pole. These hanging receptacles offer another from-the-ceiling option.

Question 53

Locate the portions of the section most susceptible to thermal bridging

Answer 53

See image

Question 54

Locate the portions of the section most susceptible to air infiltration

Answer 54

See image

Question 55

Thermal bridging happens when structure short circuits the insulation and spans clear across the assembly, touching both the inside and outside.

Answer 55

Thermal bridging is present, but not nearly as serious a problem, in wood. Concrete or steel offer more problematic paths for heat transfer.

Question 56

Overhangs–for roofs, balconies, or breaking up the scale of the elevation–are difficult to seal for air. The air leaks sprout where the structure of the overhang penetrates the plane of the building enclosure at the wall.

Answer 56

See image

Question 57

Bracing: Single diagonal, cross bracing, k-bracing, v-bracing, inverted-v-bracing (chevron bracing)

Answer 57

Bracing in a concrete structure:

Question 58

What is the area-weighted U-value of this wall

Answer 58

Answer:0.24 BTU/(hr°Fft2).

Convert each component to U-value before taking the area-weighted average.

Uopaque=1/20=0.05

Uwindow=1/1=1

Utotal= 0.05*80% + 1*20%=0.24

Generally we talk about total-building area-weighted U-value (rather than total-building R-value). Calculating the area-weighted average R-value first, then taking the inverse of that number will, curiously, return a different value: 0.06)! Weird, huh?

If you want to practice with another, similar, problem and watch a video of me working through the answer, watch this Amber Book : 40 Minutes of Competence video.

Question 59

How much heat loss through a single pane glass wall (round numbers liberally)?

Given

Glass: R=0.9

Use 19 degree design outside wintertime temperature for Roanoke, Virginia

Wall is 375sf

Qheat loss in BTU/hr = Uu-value of assembly * Aarea *∆T

Answer 59

A: Qheat loss in BTU/hr = 21,000 Btu/hr

How much heat loss through a single pane glass wall?

Given

Glass: R=0.9

Use 19 degree design outside wintertime temperature for Roanoke, Virginia

Wall is 375sf

Qheat loss in BTU/hr = Uu-value of assembly * Aarea *∆T

Qheat loss in BTU/hr = Uu-value of assembly * 375sf * 50 deg

R=0.9

U=1/R

U=1.1

Qheat loss in BTU/hr = 1.1* 375sf * 50 deg

Qheat loss in BTU/hr = 21,000 Btu/hr

*I used an indoor thermostat set point temperature of 69 degrees and rounded the answer. If you used a different indoor temperature and didn’t round, you will have gotten a similar, but not identical, solution.

Question 60

How much heat loss through the wall described below (round numbers liberally)?

Given

Bubble wrap: R=1.7 per layer

R-1 airspace

R-0.9 glass

Wall is 4 layers of bubble wrap, 5 air spaces (1/2” each), and two ¼” glass

Use 19 degree design outside wintertime temperature for Roanoke, Virginia

Wall is 375sf

Qheat loss in BTU/hr = Uu-value of assembly * Aarea *∆T

Answer 60

A: Qheat loss in BTU/hr = 1,300Btu/hr

How much heat loss through the wall described below (round numbers liberally)?

Given

Bubble wrap: R=1.7 per layer

R-1 airspace

R-0.9 glass

Wall is 4 layers of bubble wrap, 5 air spaces (1/2” each), and two ¼” glass

Use 19 degree design outside wintertime temperature for Roanoke, Virginia

Wall is 375sf

Qheat loss in BTU/hr = Uu-value of assembly * Aarea *∆T

Qheat loss in BTU/hr = Uu-value of assembly * 375sf * 50 deg

R=1.7*4+1.0*5+0.9*2

R=13.6

U=1/R

U=0.07

Qheat loss in BTU/hr = 0.07* 375sf * 50 deg

Qheat loss in BTU/hr = 1,300Btu/hr (Down from 21,000 in the previous example)

Question 61

In the previous flash cards we saw how we can reduce the U-value of an assembly to reduce heat loss. How can the “A” and “∆T” values be reduced in a building assembly?

Given

Qheat loss in BTU/hr = Uu-value of assembly * Aarea *∆T

Answer 61

Answer:

Qheat loss in BTU/hr = U * A *∆T

Reduce the area of the building skin by designing a similar-sized building in a more compact form

Reduce the wintertime inside-outside temperature differential by lowering the thermostat. This can be done with a radiant heat source, or a conversation with the owner about wearing warmer clothing.

For a detailed explanation of this series of three heat-loss flashcards, watch the video below. If you own this concept already, you can move on to the next flash cards without watching the video.

Question 62

Put these in order from most effective insulation to least effective insulation:

Answer 62

Perlite/Vermiculite: most insulative. Perlite and Vermiculite are puffy rocks that have air pockets for thermal resistance, and because they are rocks, they can be exposed to moisture without significantly degrading.

Air: more insulative than grout! Air molecules sit farther apart from one another than grout molecules, so air conducts heat more poorly than grout (which is a good thing when using empty cavities in cold climates).

Grout: pourable and cementitious, grout serves as surprisingly poor insulation, until you remember that all dense cementitious materials serve as poor insulation.

Question 63

Put these in order from highest sound transmission loss (TL and STC) to lowest sound transmission loss:

Answer 63

Grout: robust sound barriers are massive. Because of the mass of the grout, this barrier serves as an effective barrier to low-frequency sound, so it can, for instance separate a mechanical room from a conference room in a way that a lighter-weight stick wall (even one with the same STC value) is not able to.

Perlite/Vermiculite: the puffy Perlite and Vermiculite do a bit to absorb sound as it passes through the barrier, but not much. (Puffy, fuzzy things, when they are mounted at the face of surfaces, influences room acoustics–how the person speaking sounds to the listener inside the room. That requires a different discussion than the TL/STC and airborne sound isolation.)

Air: Not as good at keeping sound from the next room out (though a CMU wall, even one with only air in the cavity, is still a robust barrier relative to less massive stick-built partitions).

Question 64

In each of these four trusses, identify which members are in compression. Which ones are in tension? Assume each of them is under a uniform gravity load and supported at their ends.

Answer 64

Turss members answers

Fuck this card

Question 65

Where should I locate a “vapor barrier?”

Answer 65

Answer: on the warm side of the insulation, right up against the insulation.

This is a complex question and one that the ARE doesn’t yet understand the nuance of, because building scientists no longer use vapor barriers in assemblies to stop all vapor out-bound migration, but instead use vapor migration as a way to dry out assemblies that have become wet. However, if you see this on the exam, assume that your goal is to keep vapor from migrating out and locate the vapor barrier on the warm side of the insulation, flush to the insulation.

For a warm climate that means place the vapor barrier on the outside face of the insulation

For a cold climate that means position the vapor barrier on the inside face of the insulation

What if you have a mixed climate, like most of us do, with warm summers and cold winters? The ARE doesn’t seem to know what to do in that scenario, so that is unlikely to be encountered on the exam. To learn more, read on. . .

These enclosure questions are by far the most common questions I get from those in practice—and for good reason, because enclosure is the most labyrinthian area of building science, and among the most complex.

Your building skin will need to (in order of importance)

Keep out rain: rain control layers
Keep out outdoor air: air control layer
Keep out cold/heat: thermal control layer
Dry out when the assembly gets wet (and throttle the rate of vapor migration into the cavity, but contrary to popular opinion among those in our field, providing for vapor out-migration is more important than preventing vapor in-migration): vapor control layer

Question 66

Identify, in your own words, what each of these HVAC terms means. Say your answers aloud or write them down.

Condenser

Compressor

Evaporator

Air-to-air system

Air-to-water system

Water-to-Air system

Water-to-water system

Split system

Minisplit

Swamp cooler

Evaporative cool tower

Cooling tower

Chiller

Air-handling unit

Fan coil unit

Direct expansion (DX)

Variable vs constant systems: as applied to cooling coil, ducted air speed, fan, or pump

Geothermal system

Chilled beams

Answer 66

Cooling system terminology

Condenser: high-pressure hot refrigerant

Compressor: pump that circulates refrigerant

Evaporator: low pressure cold refrigerant

Air-to-air system: fan over condenser and evaporator

Air-to-water: fan over condenser, pumped water over evaporator

Water-to-Air: pumped water over the condenser, air over the evaporator

Water-to-water: pumped water over the condenser and a different pumped water system over the evaporator

Split system: condenser outside, evaporator inside (residential)

Minisplit: refrigerant flows through units in rooms under high pressure for heating and low pressure for cooling; can heat and cool different rooms simultaneously.

Swamp cooler: uses evaporation of water for cooling, with a fan, for very dry climates only

Evaporative cool tower: uses evaporation of water for cooling, no fan, for very dry climates only

Cooling tower: for cooling condenser water by blowing outside air over it

Chiller: refrigeration machine for cooling chilled water in large buildings. Includes refrigerant moving through the condenser, compressor, evaporator, and expansion valve and the water that interfaces with the evaporator (and condenser)

Air-handling unit: located down the hall, cools air for delivery to the room via ductwork

Fan coil unit: located in the room, cools air by blowing it over pipes filled with chilled water from a chiller

Direct expansion (DX): like a window unit; with all cooling components including refrigeration machine and fan in one box

Variable vs constant cooling coil & variable vs constant ducted air speed & variable vs constant fan & variable vs constant pump: how much control over the rate of flow. Variable generally offers more comfort control and more energy-efficiency, but more complex equipment

Geothermal system: More efficient because it uses the moderate temperature of earth to heat or cool water for the refrigeration machine

Chilled beams: like radiators for coolth; measures are required to prevent condensation

For a more detailed explanation, I made this video. To watch the whole Amber Book : 40 Minutes of Competence video series (not necessary if you took this course and followed it, because it repeats what you saw in these flash cards. . . but maybe helpful for re-studying a concept or two that troubled you), go here to the unlisted YouTube channel playlist.

Question 67

Why are lab buildings big energy hogs?

Answer 67

Air quality concerns usually prohibit labs from recirculating room air back to the air handling unit. The fear is that the chemical or biologic that you spilled in your room will spread, airborne, throughout the rest of the building via ductwork. So to cool my lab building in the summer, all the inside air that had already been cooled to 70 degrees and 70 percent humidity is exhausted out to the atmosphere and replaced with new outside air that will need to be cooled and dehumidified all the way down from 90 degrees and 90 percent humidity. This is much less efficient than recooling indoor air. The graph depicts the energy use per square foot of floor area for different buildings on my university campus. Note the outsized footprint of the research buildings, which primarily stems from their inability to recirculate conditioned air.

Question 68

What building type is most associated with chilled beam technology?

Answer 68

Labs are most associated with chilled beam technology.

Chilled beams have nothing to do with structure. Rather, chilled beams are to cooling as radiators are to heating. They are cold surfaces in the ceiling, made so with circulating water from the chiller. They cool the air through convection and cool the occupants through radiation. Common in Europe, chilled beam technology has been slow to gain widespread popularity in the US, probably because it’s complicated to install and operate, or maybe just because air systems are entrenched in the minds of MEP engineers, architects, and building owners.

There is, however, one building type where the advantage of chilled beams overwhelms the inertia of the entrenched air systems: Labs, especially lab buildings in warm climates. Chilled beams, because they don’t rely on moving around streams of (contaminated) air for cooling, offer an energy-efficient solution.

Question 69

Why does the advantage of chilled beams overwhelm the inertia of the entrenched air systems in lab buildings.

Answer 69

For air quality reasons, labs can’t recirculate their air. If chilled beams are used in lieu of a ducted air system, we no longer have to exhaust that perfectly good 70 degree room-temperature air and replace it with 100% outside fresh air that needs to be mechanically cooled all the way from 90 degrees. Instead, when the thermostat calls out, “more cooling, boys!” we can circulate chilled water to the chilled beams (radiators in the ceiling that look like this). This is a much less wasteful regime, and there’s no worry about your aerosolized lab spill being blown through all the rooms of the building because there’s no recirculating ducted air needed for cooling. (Some small amount of ducted fresh air is still required, but those duct sizes are often small and they never siphon bad air from other rooms.)

Question 70

We use plywood shear walls in wood construction to resist lateral forces in the two vertical dimensions (X-Z and Y-Z planes). How do we resist lateral loads in the horizontal (X-Y) plane?

Answer 70

Wood diaphragms, usually the kind of plywood or OSB panels over joists or rafters that we need for gravity loads anyway in our floors and roof, also double as our “resister of lateral loads” in the (X-Y) plane. Think of them as shear walls turned on their sides to be horizontal.

Plywood diaphragms can be seen here and here. Most wood-framed floors act as diaphragms, whether they were intentionally designed as such, or not.

Question 71

You are calculating the reverberation time in an opera house. It is the early stages of design, so you will be working with approximate area values because the space hasn’t been laid out yet. You assume 10,000 square feet of floor area, 10,000 square feet of total wall area, 10,000 square feet of ceiling area, and 10,000 square feet of seating area (over top of the already-mentioned floor area). 2,000 square feet of the 10,000 square-foot wall area will be covered by absorbing material (fabric-wrapped glass fiber panels). How many square feet of material, in total, will you be using for your calculation?

Answer 71

Answer: 28,000

The sound in the room will not “see” the 2,000 square feet of hard wall that is behind the soft panels, so we won’t include that area.

The sound in the room will also not “see” the 10,000 square feet of floor that is covered by the audience seating, so we won’t include that floor area either. Seating area replaces the floor area it covers when accounting for room acoustics.

Question 72

Types of security systems. . . .

Answer 72

CCTV: Closed-circuit television. Cameras record the premises for security. Types of cameras: conventional, thermal (for night vision), PTZ (Pan, Tilt, and Zoom cameras so you can cover a larger area while minimizing the number of camera installations), and domes (so the retail workers at the cash registers can’t see where the camera is pointing)

Access control systems: Restricts entry by pin, fingerprint, or biometric pattern identification system.

Motion sensors: To detect movement with infrared rays. . . Active motion senors send out radar and let the system know when something has moved. Passive motion sensors send out nothing but monitor with a thermal camera and wait for a change in heat (because someone who shouldn’t be there moved). Don’t tie active sensors to lights that illuminate the suspect, because windblown bushes, small animals, and even insects can trigger a false alarm, which are very common. Passive sensors can be tuned to be more or less sensitive so that human movements can be detected above a sensitivity threshold, but those of a raccoon won’t trigger the system.

Fiber optic detection systems: a fiber optic cable is woven through a fence or wall. When the intruder climbs the cable shakes and the alarm sounds.

Some of these systems can only be applied to securing the property perimeter (fiber optic detection system). Others can only be applied to securing access at doors (fingerprint access control system). Some can be used for either securing the perimeter or securing access (CCTV).

Question 73

Displacement ventilation

Answer 73

Displacement ventilation: mechanical cooling, supplied near the floor, with a little-bit-cold air brought in at not-very-fast duct velocities. This displaces the warmer room air near the floor and pushes it upward. Grilles in the ceiling suck out the warmer return air (also slowly). Because our skin is warm, naturally convective plumes form where the people sit, drawing warm air up toward the ceiling grille and replacing that air with the colder pool of heavy air near the floor.

Benefits: uses less energy (smaller & slower fans, 65 degree supply air instead of 55 degree supply air, more hours available for the economizer cycle “free cooling” because 65 degree outdoor air can be brought directly into the space); is quieter (slower fans); and provides superior air quality (the stalest room air is the warmest, so the stale air hovers at the ceiling near the return grille, where it can be filtered and exhausted outside).

Limitations: only works in rooms with high ceilings (minimum 9′); doesn’t work with heating (so you’ll need radiant baseboard heating for winter); doesn’t do as well in humid climates (cooling air to 55 degrees removes more of the room humidity as condensation at the cooling coil than cooling the air to only 65 degrees); with high cooling loads, occupants can feel uncomfortable (with cold feet and warm head).

Used for: high-occupancy rooms (lots of people so lots of stale air to be removed); theaters (tall ceilings, need quiet); cooler climates (popular in northern Europe)

Question 74

When do architects use a Faraday cage?

Answer 74

Architects use Faraday cages as lightening protection. By creating a wire mesh on the roof, they can redirect lightening strikes around the building to the ground. See this diagram.

Question 75

Embodied energy

Answer 75

By comparing “embodied energy” between building materials, we can specify with climate change in mind. A lower value translates to a smaller energy footprint (by weight). Embodied energy only accounts for the energy required to mine, extract, process, and transport the material. . . just the upstream part. To include the operation (how much energy will the insulation save? How much energy will the photovoltaic panels make? How long will the gypsum board last? Can rubber be recycled?) one must supplement an embodied energy analysis with a life-cycle analysis (LCA).

Question 76

Which flooring should be used from an embodied energy point of view?

Answer 76

A: Rammed earth certainly has the least embodied energy at 0.5 MJ/kg. But perhaps that’s not practical for a high-traffic fifth-floor office.

the next-lowest embodied energy option is stone flooring at 2 MJ/kg. . . but note that although wood, at 10 MJ/kg, has a 5x higher embodied energy per kilogram, stone is heavier–therefore we require five times as many kilograms of stone to cover the same floor area. That puts the two options at about-even: wood has five times the embodied energy per kilogram as stone tile, but stone tile weighs five times as much as wood.

Question 77

So what did we decide for the flooring: stone-tile or wood?

Answer 77

We have to ask ourselves more questions first. What was given as “stone” is an average, but in embodied energy analysis, knowing the specifics is annoyingly important. Look at the difference within “stone.”

Then we must account for the variance associated with transportation. Stone has weight, and heavy things require a good deal of fuel to transport. Is the stone tile mined locally, or is it shipped from India?

The takeaway: The flaw of averages strikes again! To get embodied energy right, you’ll need to do a lot of research (manufacturers and suppliers notoriously use this to greenwash). I think your design time is better spent researching low-energy operations (VRF HVAC, daylight harvesting, roof albedo, insulation, low-e windows etc.) and only after that’s buttoned-up should you research low-energy materials. . . but I don’t know that NCARB shares my priorities on this issue, so we’re studying embodied energy now.

Question 78

So we should choose wood, right? Let’s choose wood.

Answer 78

Wood must be finished, and paints, lacquers, and chemical finishes of all kinds have an embodied energy problem:

But again, measuring these by kilogram may be a bit misleading: how many kilograms of finish does it take to cover a square meter of wood flooring? We’d want to calculate that, add the embodied energy of the wood itself, and compare the total (wood + finish) to stone.

The take-away: paints, lacquers, finishes, resins, and epoxies include high embodied energy content (they often off-gas too). Consider a no-finish option when possible, like an exposed ceiling, or an alternative like sandblasting, or shou sugi ban (but note that I used this burnt wood technique on my shed and the char streaked any clothes that brushed up against it. . . so I wound up applying a clear stain on top of the burnt wood anyway!) To see, go here (second to last photo, bottom-right of photo).

Question 79

With an eye toward carbon emissions, what should you select as structure: steel or concrete?

Answer 79

This is, again, a difficult question. Concrete is heavier per-unit-volume, but we use sooo much more volume of concrete in a concrete building than volume of steel in a steel building (plus a non-negligible amount of steel rebar inside that concrete too). The real problem, though, is that embodied energy is only part of the story when selecting for climate and carbon. The process of making cement directly produces carbon dioxide when calcium carbonate thermally decomposes, leaving behind lime and carbon dioxide; this is separate from carbon emissions associated with the energy used in cement production.

The takeaway: That seemingly-tiny concrete bar on the graph belies a thorny problem: Concrete contributes 1/12th of all the carbon that humans spew into the atmosphere. If concrete were a country, it would rank third–behind only China and the US–in carbon emissions! The convention of measuring embodied energy by weight (instead of by volume or by square foot or by building), coupled with the focus on embodied energy rather than on carbon emissions, must be one of the biggest wins for the concrete industry–or any industry– ever. I don’t know that they orchestrated that convention, but they milk it to make concrete seem benign when architects do a quick google search. I’m not sure that NCARB understands this, but you should.

Question 80

A gaming floor measures 24 feet by 20 feet; what is its maximum occupant load? Use this code link to answer.

Answer 80

A: 44 occupants

Many of the code table-reading questions you will face are this straightforward. . . don’t doubt your answer, as the ARE code test items generally shy away from obscure exceptions.

From the link table, 1004.1.2, search for the “weird” word (gaming); we find that we can calculate an occupancy load of 11 sf/occupant.

The gaming floor measures 24 ft x 20 ft = 480sf

480sf / 11 sf per occupant = 44 occupants

Question 81

A corridor serving a one-story office building has two exits as drawn. The conference room has one door to the corridor. The building is sprinklered. What is the maximum length of travel from the far corner of the conference room to the conference room door? Use this code link to answer. This one too.

Answer 81

A: 100ft, minus the required travel distance in the corridor until you have two means of egress.

The first link isn’t relevant to this question. From the second link table, we find that a Business (B) occupancy class sprinklered building has a maximum common path of egress travel distance of 100ft. This means that from the most remote corner of the room, farthest from the exit, our fleeing occupant must travel no longer than 100ft before having a choice as to which way she will flee. She can go left past the reception desk, or she can keep running straight down the corridor.

Generally, the occupants of your building can travel no more than 75 ft before they have a choice of at least two ways to egress (this particular situation allows for 100 ft). Watch this excellent short video here.

Some of you who are savants at reading plans to scale may have noticed that the dashed line here is longer than 100 ft– and is probably drawn at 140 feet in this example. So even if your conference room can be 4,900 sf by occupancy load, per the previous flash card, the travel distance may limit the size of your room (or require an egress door from the conference room directly to the outside, or a corridor reconfiguration so that occupants have a choice of two egress paths right when they leave the room, without having to travel right down the hallway).

Question 82

A corridor serving a one-story office building has two exits as drawn. The conference room has one door to the corridor. The building is sprinklered. The corridor has an offshoot with a dead end. What is the maximum length of the dead end portion of corridor? Use this code link to answer.

Answer 82

A: 50ft

Search the link for “dead end” and you’ll find section 1018.4 Dead Ends. Use search when faced with a case study exam question too.

Where more than one exit or exit access doorway is required, the exit access shall be arranged such that there are no dead ends in corridors more than 20 feet.

So the limit for a dead end corridor is 20’. . . but wait: read on and find

In occupancies in Groups B, E, F, I-1, M, R-1, S and U, where the building is equipped throughout with an automatic sprinkler system, the length of dead-end corridors shall not exceed 50 feet.

We are Group B, so our dead end corridor limit for a sprinklered office building is 50ft.

Dead ends are generally limited to no more than 20′ (50′ if the building is sprinklered). Watch this excellent short video here.

Question 83

The conference room has one set of doors to the corridor. The building is sprinklered. What is the minimum total width of the door(s) to the corridor? Use this link.

Answer 83

A: a single 32 inch clear required for the door (36″ wide door when accounting for the hardware and door thickness).

Door width based on occupancy load: at 49 people x 0.15 inches per person = 7.35 inches

But minimum width of door(s) is 32 inches clear, so that will govern.

Watch this excellent video for an explanation. Watching this is a must if you don’t research code a lot at work.

I know I told you not to waste time memorize code, but memorizing the following rule of thumb may save you enough time searching the case study on exam day to make memorizing worthwhile:

Question 84

A corridor serving a one-story office building has two exits as drawn. The conference room has one door to the corridor. The building is sprinklered. What is the most that the door can encroach into the corridor and still maintain the corridor’s proper egress clearances? You may search this code excerpt or google for your answer.

Answer 84

A: When fully opened the door may not reduce the required clearance by more than 7inches. . . and at no position can it reduce the required width by more than one-half.

This second requirement–that the door not block more than half the corridor egress width when open to 90 degrees– often isn’t met without some intentionality on the part of the architect. For example, assume an occupant load fleeing down the corridor at 240 persons. The corridor required width may then be 240 people x 0.2 inches per person = 48 inches wide. (We would instead multiply by 0.3 inches per person were the building unsprinklered.) If we design a corridor at that minimum 48 inches wide, and we open the 36″ door into the corridor because doors must swing in the direction of fleeing people, you can see how a 36″ door will easily block most of a 48″ corridor.

We may then increase the corridor width beyond the 4 ft egress requirement and widen it instead to 5 ft to account for the door swing blocking 3 ft of the corridor. Even though the corridor is now 5 ft wide, we need 4 ft for egress; and with the door at 90 degrees, we need half of that, or 2 ft clear. Now, nominally, when the door swings three feet into the 5 ft-wide corridor, we can know half of the required 4 ft corridor width is maintained.

Alternately, we may put the door in a recessed niche so that the door, when opened to 90 degrees, fails to block more than 7″ of the corridor. You’ve seen this trick a million times, but may not have noticed it. Something like this.

Question 85

Fire wall vs fire barrier vs fire partition

Answer 85

Fire wall: most stringent–you essentially build two different buildings, structurally independent of one another. Separates two construction types or two different areas. Extends from foundation through roof.

Fire barrier: more common–extends from floor to underside of structural ceiling and does not need to be structurally independent. Required for mechanical shaft walls, egress stair walls, separated uses, and incidental uses.

Fire partition: least stringent–can be made out of wood and can include a dropped ceiling (doesn’t have to extend to the deck above). Required for corridors.

Question 86

How deep should the bottom of a spread footing be in a climate with a frost depth of 60″

Answer 86

A: 60″

If you don’t go deep enough, freeze-thaw cycles will heave your foundation.

In older code versions frost depth may have measured from grade to the top of the footing. . . now the measurement is to bottom of the footing.

Question 87

What do we use geotextiles for (name every use you can)?

Answer 87

Geotextiles, which may look like a woven mesh or like a plastic tarp, can be buried to strengthen soil (e.g. for foundations), stabilize soil (e.g. for parking lots and roads), separate different strata of soil (fine-grain aggregate from coarse aggregate), prevent erosion (e.g. along a stream bank), keep out weeds (in a garden), keep water out, allow water to filter through, or seal soil to keep contaminants in. . . or out (e.g. for landfills).

Question 88

What is a variable refrigerant flow (VRF) HVAC system?

Answer 88

Pumps and manifolds move refrigerant to spaces that need heating (high-pressure refrigerant gets hot); and pumps and manifolds move refrigerant from spaces that need cooling (low-pressure refrigerant gets cold). An in-unit fan blows air over the refrigerant coil in each space. Because we can simultaneously heat the perimeter while cooling the core–just by moving refrigerant between the two–this type of system can often be your lowest-energy option.

The ductless mini-split system we covered is a type of VRF.

To watch more on VRFs, click here.

Question 89

You’re designing a renovation of a post-tensioned concrete building. Why is it difficult to simply drill a hole in the floor to run a new vertical pipe?

Answer 89

You could inadvertently core through one of the post-tensioning cables! It’s not that unlikely as you might think– there are lots of hidden cables to accidentally cut (see here). We have slab-penetrating sonar tools to find the cables so you won’t compromise the entire structure with your hole.

Question 90

Should crawl spaces be ventilated or sealed?

Answer 90

Old thinking: crawl spaces may be ventilated or sealed.

New, evidence-based, thinking: crawl spaces should be sealed: treat them like (small) basements and think of them as part of the building’s thermal enclosure. Underlay them with gravel, plastic sheeting, and a concrete slab to keep out groundwater, insulate the walls (but not the overhead plane), and heat/cool them just like the house.

Before a renovation, this crawlspace had been the worst possible option. It was neither ventilated, nor part of the thermal enclosure: insulation had been on it’s overhead plane, below the house floor. The room had a dirt floor, exposed to groundwater; the room required a dehumidifier all summer long. This photo captures the after-renovation crawlspace with plastic sheeting over the dirt floor, insulated walls, and an absence of overhead insulation.

Question 91

What shape offers both the best resistance to torsion and the least resistance to wind?

Answer 91

A: The circle offers the most resistance to torsion and the least resistance to wind.

circular-cross-section columns offer higher resistance to torsion (think about twisting them from above) and circular building structural forms offer the highest resistance to torsion. If you can’t picture this, click here for a video explanation.

Question 92

What is automatic dimming?

Answer 92

When the sun emerges from behind a cloud, photosensors in the ceiling automatically dim the electric lights, especially those near the window, to save energy.

Dimming is usually associated with offices because they are occupied during the daytime and have relatively constant light targets.

Question 93

Without specific prior knowledge, how do you pick which material is less expensive? How do you pick which material is more thermally efficient?

Answer 93

If you have experience working with clients who build cheaply, or if you’ve ever observed a spec strip mall go up, assume that the strip mall’s material choice is the least expensive. . . .

Stucco (EIFS) must be inexpensive by that metric. Same with stick-built structure (2x4s), PVC piping, precast concrete, gravel pathss & roads, local subcontractors (out-of-town contractors need hotel rooms paid for), vinyl flooring vinyl siding & vinyl windows.

And if a newer technology has almost-entirely replaced an older technology, assume that the newer technology is some combination of less expensive, easier to install, or more efficient thermally . . .

EPDM (rubber roofing) must be better than hot-mop (asphalt built-up roofing) by that metric. Same with air barriers, Energy Star appliances, and drainage mat (instead of gravel) at basement walls.

Question 94

You likely will be asked which HVAC system to use for a specific building type or occupancy use.

When thermal control is prioritized, like if each hospital room, dorm room, hotel room, or apartment needs to set its own thermostat and some rooms need heating and some need cooling and some need neither. . . at the same time: which system should you use?

Answer 94

A: Fan coil units, ducted systems with variable air volume (VAV), and variable refrigerant flow (VRF) systems like ductless minisplits

Direct expansion (DX) systems (like window units or through-the-wall systems with a compressor in each room) allow for thermal control, but are unlikely to be used because they are inefficient, loud, facade-ugly, and expensive to maintain.

Question 95

When there’s no room for ducts. . . you’re renovating a historic building and there’s no dropped ceiling to hide the duct work or you’re building with low floor-to-floor heights so there’s no room above or below for duct work: which HVAC system should you use?

Answer 95

A: When there’s no room for ducts, use either (1) a hydronic system pumping hot and cold water around the building in small pipes instead of air in large ducts or (2) a variable refrigerant system (VRF) pumping high- and low-pressure refrigerant around the building in small pipes instead of air in large ducts.

Piped (ductless) systems include: fan coil units or chilled beams served by a central chiller, fan coil units served by a central boiler, in-room evaporator/condensers served by VRF (like ductless minisplits)

Rooftop package units (RPU) can cool the space directly below them without running duct work, but they are noisy, ugly when visible, and inefficient (it’s cold on the roof in the winter and hot up there in summer)

Attic or crawlspace insulation may be added, and high-efficiency equipment may be specified, to improve energy use without tainting the historic character.

Question 96

When energy-efficiency is a priority: which HVAC system should you use?

Answer 96

Energy-efficient systems are (1) central chiller and AHU systems with fewer compressors and fans to run, (2) renewable systems like active solar where the sun heats up hot water that, in turn, moves through a thermosyphon piped loop, (3) waste-heat-capturing systems like variable refrigerant systems (VRF) (ductless minisplits are an example of VRFs) and systems that circulate leftover heat from a hot water heater or other combustion process to a pool or radiant floor, (4) systems that leverage the temperature outside or underground like economizer cycles that allow us to use cold outside to air-condition for “free” or geothermal systems that allow us to use mild temperatures underground, (5) dedicated outdoor air systems (DOAS) that allow for fresh air in separate ducts so we can turn off the AC while still maintaining air quality, (6) all-electric heating systems (A/C is almost always all-electric anyway) in municipalities where electricity is generated with renewables, and (7) radiant and displacement ventilation systems that allow us to lower the thermostat in winter and raise it in summer while maintaining the same level of thermal comfort, like radiant floor heating, radiant ceiling cooling, old-fashioned radiators, chilled beams, and displacement cooling with from-the-floor slow air.

Can you believe you just understood (most of) that? Nice work, and treat yourself to a nice meal to congratulate yourself on how far you’ve come since starting!

These systems are the future, and if your firm or mechanical engineer aren’t specifying them, be a hero and change that.

Question 97

When quiet is a priority: which HVAC system should you use?

Answer 97

Systems with far-away central compressors and far-away central fans. . . or radiant systems with no fans at all.

Question 98

You may be given some systems as options that are almost always the wrong choice. Which systems are so clumsy or inefficient that you can eliminate them straight-away?

Answer 98

Direct expansion (DX): noisy, expensive, facade-ugly

Multi-duct: use too much building volume for duct work

Dual duct: inefficient–heats and cools air and then mixes the two to get to the right temperature

Swamp cooler: low-energy, but brings unwanted humidity into the space

Question 99

An architect designing a mixed-use building must decide on HVAC system types. The building includes 24 apartments on two floors, two different office tenants, each occupying all of a single floor, and a single retail store occupying the entirety of the ground floor. The client would like to maximize thermal control in each apartment; allow for thermal control, minimize noise, and minimize equipment maintenance in the offices; and minimize noise and minimize equipment maintenance in the retail store. She would also like to easily meter each tenant so each can be properly charged for the amount of heating and air-conditioning they use. The basement includes a central chiller and central boiler. Select an HVAC system for each occupancy type. You may use a system for more than one occupancy and not all the systems need to be used.

Systems:

Central AHU with multiduct system

Central AHU with varable air volume (VAV)

Central single-zone AHU

Fan coil units

Answer 99

Apartments: Fan coil units (easily metered and high thermal control but loud)

Offices: Central AHU with variable air volume (VAV) (pretty good thermal control and quieter)

Retail: Central single-zone AHU (excellent thermal control (one thermostat), quiet, and easily-metered with one tenant served)

Before 2000, offices typically got VAV and apartments/dormatories/hotel rooms/patient rooms typically got fan coil units. With more sophisticated control systems and digital simulations available, a focus on low-energy and quiet buildings, and more knowledgeable clients, came a better, but less reductive and less predictable regime whereby variable refrigerant and radiant cooling are now specified more frequently. NCARB either doesn’t know this yet or their volunteer non-expert test item writers are hamstrung by the inherent difficulty in writing questions to reflect the new complexity. So stick with the old strategy, laid out above and on the previous card.

Question 100

You are designing a high school football stadium with an elevated drum major platform at 24″ high. Do you need a railing? (A drum major is the member of a marching band that directs the others in the band.)

Answer 100

No railing required for heights below 30 inches.

Railings would (probably) be required for a drum major platform–or deck, walkway, or any floor–above 30 inches. Exceptions that don’t need guards: the loading side of loading docks and the audience side of performance stages

To see a (low) drum major platform without a railing, see here. To see a (high) drum major platform with a railing, see here.

Question 101

When is tempered glass required? When is laminated glass required?

Answer 101

Tempered glass: 5x stronger than untempered annealed glass. Required at storefront door (or glass panel adjacent to a door) like this where the glass extends to 18″ above finished floor. Less likely to break if you back your rolling suitcase into it, or walk into it with your body accidentally. Shards are less jagged than untempered annealed glass.

Laminated glass: stronger still and when it breaks, shards generally stay glued to the laminate like this. Laminated glass is required for skylights, and hurricane-prone regions, as well as security-sensitive rooms like prisons, mental hospitals, or casino cashiers. Laminated glass can also be used instead of tempered glass in glass doors and adjacent panels.

Question 102

What is an impact load?

Answer 102

Load of short duration, like a large tree limb falling on a roof.

Question 103

Print out and fill out this final four bracket for your current design project at work in the same way you would for March Madness. It’ll be fun and useful for the exam.

Answer 103

Click here to visit an Amber Book : 40 Minutes of Competence and review of all of those terms on the bracket. It’s a long video, so skip ahead past any terms or concepts you already have a good handle on if you are facing a deadline at work or anxious to finish the course and get to the exam.

Question 104

Noise control

Answer 104

Watch this Amber Book : 40 Minutes of Competence video. Be sure to pause when I ask a question and answer it in your own works aloud.

Question 105

A new office building is being constructed in a seismically active locality. For greatest efficiency, where should the lateral steel bracing be inserted relative to the primary structure (columns and beams)?

Outboard of the primary structure (like this)

In-line with the primary structure (like this)

Inboard of the primary structure (like this)

Answer 105

In-line with the primary structure provides the most stability.

When in doubt, answer in a way that is consistent with what you’ve most often seen in the field.

Question 106

The problem with lights recessed in the ceiling:

Answer 106

On the top floor with an unconditioned attic above, they offer an unwanted short-circuit path for infiltration (at their perimeter if unsealed) and thermal bridging (interrupts the cavity insulation). See here.

Recessed lights can (rarely) be integrated with exhaust fans (see here) so that excess heat from the fixture is exhausted with the air we need to bring out of the building anyway, and because LEDs otherwise have a hard time shedding the heat they create. . . but you wouldn’t want to blow supply air over your lighting anywhere you need cooling because who wants to warm air used for cooling?

Unless special fixtures or construction techniques are used to box around the fixture in the cavity, recessed lights can ruin the fire rating of a ceiling. See here.

On any other floor with an occupied space above, they offer an unwanted short-circuit path for noise (both airborne noise and impact noise from footfall). To read a booklet I once wrote on the topic of noise control in multi-family design, go here.

People often ask me why I titled this course Amber Book. Read on if you are curious. . .

The link to my booklet, above, is titled “The Acoustics of Multifamily Housing: For Architects, Builders, Developers & Architects.” I had written the booklet for an Acoustical Society of America grant and then went for a run to figure out the cover. I envisioned it as a rarely-used, but important-to-find-on-your-bookshelf-when-you-wanted-it affair. Because it was thin, it would need a solid color and spine if it were to be ever found at the beginning of a condo design process. I came up with “The Orange Book” because yellow book, green book, red book, and black book already had been taken in the popular imagination–and Orange, to my knowledge, was virgin soil. Plus, it’s always more fun to think about a color named for a food (lime green, for instance). Once published, no one ever called this booklet by its formal title. . . they just called it “The Orange Book.”

So when creating this course, I borrowed that template when titling it: a color that also has another meaning (the amber gemstone).

I’ve since created an animated video course for visual high-schoolers studying for the ACT or SAT: Olive Book! . . . Easy to remember because everyone has a strong feeling one way or another about olives. I hate them.

If I make another course, which I have no immediate plan of doing at the time I write this, I’m thinking about “Copper Book,” but I’m open to other color suggestions if you have one, provided the color also has another meaning.

Most people think I named the course after a girl, but the real story is so much less interesting.

Question 107

To quiet a mechanical system: put fibrous insulation inside the duct or outside the duct?

Answer 107

A: Inside the duct

Interior duct insulation (typically 1″ thick) is remarkably successful at quieting fan noise. There’s nothing as effective. Lining the outside of the duct does nothing acoustically (but will keep the air colder (or warmer) over long distances, so can help with thermal control, efficiency, and preventing condensation on the outside of a cold duct).

Building scientists harbor concerns that the fibers in interior duct insulative lining may deteriorate, loosen, and be carried down the airstream to our lungs (likely carcinogen). Click here to be haunted. They also link glass fiber interior duct lining to microbial growth: allow dust and moisture in a fibrous dark medium that can’t be cleaned and then run room supply air over 100 feet of that medium for fifty years. . . spores!

Fabricators make duct insulation with an (expensive) perforated metal lining to ameliorate air quality concerns without losing (much of) the noise-quieting of interior glass fiber duct insulation; see here. Closed-cell foam duct insulation is marketed as a compromise because there are no fibers to come loose or harbor microbes, but it proves ineffective at any meaningful noise control; see here.

I’ve been disappointed to find my colleagues in the architectural acoustics community are generally dismissive of the air quality concerns associated with one of their most reliable noise control tricks. And I don’t know that NCARB is aware of this air quality trade-off, but you should be.

Question 108

When given a choice on the exam, how do you decide the relative cost of design decisions if you don’t have experience in this realm?

Answer 108

Labor is likely the deciding factor, especially if that labor is technical or specialized. That’s why the screen that you are looking at now was assembled overseas. This Forbes article claims that an iPhone made entirely in the US would cost $50,000!

Expensive labor:

Those who install technical equipment (HVAC contols)

Steel erectors welding ten stories in the air

Crane operators

Out-of-town specialists (Factory floor machine assemblers)

Masons

Anyone doing something more time consuming than it would otherwise be (Disassembling or recycling instead of demolishing)

Specialized trades associated with historic preservation (ornamental plasterers)

Finish carpentry

Anything that the crew hasn’t ever built before (a bubble wrap wall panel)

Union labor

Labor sourced without competitive bidding

Generally less-expensive labor:

Drywall

Light wood framing

Demolition

Roofing (unless very steep roof)

People who build things that no one will ever see (foundations, insulation)

Anything a homeowner thinks she could probably learn to do herself

You will find approximately 10 exam questions related to the cost of design decisions. I don’t think that memorizing building material cost is a good use of your time: so much to know, so few questions. That said, understanding principles like this will help you get about 7 of the 10 correct, without having to memorize anything.

Question 109

On the truss below, what type of connections are found in the circle? Fixed or hinged?

Answer 109

A: hinged

Question 110

In the truss below, which type of connections are in the circles? Fixed or hinged?

Answer 110

Hinged

Question 111

In the truss below, which type of connections are in the circle? Fixed or hinged?

Answer 111

A: hinged. . . the geometry of triangles allows almost all internal web connections to be hinged.

Question 112

In the truss below, which type of connections are in the circles? Fixed or hinged?

Answer 112

A: Fixed

The geometry of triangles allows almost all trusses to have hinge (pin) connections in their webs. . . The exception is the Vierendeel truss, pictured below. No triangles means no hinges: the connections must be fixed.

Architects use Vierendeel trusses because, though more expensive and not as strong for a given depth and weight, they more easily allow for window openings because of their right angles. See here. Like the Trombe wall, Vierendeel trusses probably have a more prominent place in the imagination of architects than in the buildings they design: 20th-century relics–whose performance didn’t live up to their engineering promise-that continue to echo in the test items that NCARB reuses.

Question 113

Why is the melted snow on this roof between the rafters?

While the melted snow on this other roof is at the rafters?

Answer 113

This (below) is a ventilated attic. The thermal envelope doesn’t include the attic because the insulation sits on the attic floor. Heat from the house rises up to the attic, making it (slightly) warmer than the outside air. That heat continues to rise to the rafters. There’s no insulation between the rafters, so the snow melts between the rafters before the snow at the rafters where the wood structure adds some small amount of extra insulation.

This (below) is an occupied attic. The thermal envelope includes the attic because the insulation sits on the attic ceiling between the rafters. Baffles allow outside air to creep up the gap between the rafters, outside of the insulation, but inside the roof. Heat from the occupied attic rises upward, thermally bridging across the rafters, melting the snow at the rafters. the spaces between the rafters remain cold because the baffles bring in outside air above the insulation to the gaps.

This metal structure is especially heat-conductive!

Question 114

From an accessibility point of view, you’ll need to provide enough clearances around doors to allow for a wheelchair or walker, plus the door swing. How much room do you need to allow around a door?

Answer 114

You don’t have to memorize this. . . but you may be asked to understand this diagram if you see it. The dashed lines can’t have a wall pilaster, fire extinguisher cabinet jut-out, column, pinch-point, or anything else blocking the way.

Question 115

Given the same number of fixtures per square feet, which room has more light at the desk plane?

Answer 115

The low-ceiling large room (proportions of a tuna can) has more light reaching the desk than the high ceiling narrow room (proportions of a straw).

Why? Imagine that we instead measure how much water reaches the floor from a sprinkler on the ceiling, and the walls absorb water because they are wallpapered with sponges. In the water example, you can see how the tall, skinny, room’s walls will absorb more of the water on its way down to the floor. Similarly with light: the tall skinny room’s walls absorb more of the light as it bounces between walls on its way downward to the work plane at desk height.

The tall skinny room has a HIGHER room cavity ratio (2.5 x total wall area / total floor area) and a LOWER coefficient of utilization (percent of light available in the room reaching the work plane)

The short wide room has a LOWER room cavity ratio (2.5 x total wall area / total floor area) and a HIGHER coefficient of utilization (percent of light available in the room reaching the work plane)

We use room cavity ratio (RCR), in concert with the color (reflectivity) of the room’s surfaces, to determine the coefficient of utilization (CU). We use CU to determine how many light fixtures we need in a room to sufficiently illuminate it. CU is part of a formula given in the reference material available under the electrical tab in the exam.

Read this card again and again until you understand the relationships involved. To see an example table translating cavity ratio and ceiling + wall reflectance into a CU for a given light fixture, click here. Run through the numbers: you can see that lower cavity ratio values (y-axis) and higher room reflectances (ceiling, then wall, on the x-axis) beget higher CUs. Keep working at this until you understand it.

Question 116

This is the first in a series of seismic failure photos that you’ll need to be familiar enough with to identify.

What caused this failure?

Answer 116

A: Strong beam, weak column

We generally design buildings so that the beams fail before the columns. When the columns fail before the beams, the building may undergo a complete collapse.

Question 117

What’s the potential seismic problem?

Answer 117

A: perforated shear wall (bottom-right) . . . shear walls must extend foundation to roof to work correctly in an earthquake

Question 118

What caused this seismic failure?

Answer 118

A: Re-entrant corner/Irregularly-shaped building. Simple forms perform best in earthquakes.

Question 119

What caused this seismic failure?

Answer 119

A: Variations of perimeter strength and stiffness.

Question 120

Why do we use seismic isolation?

Answer 120

See image

Question 121

SD cost estimating technique?

Answer 121

“Unit-rate cost estimating”

We start at programming with a “rough order of magnitude” cost estimate (might be off by as much as 2X), used for a “napkin estimate” before design to determine feasibility. Used in Pre-design/programming (PA exam)

As we move through design phases we get more specific and have more confidence that our estimate is close to the final construction cost; eventually, we want our estimate to be within 5%.

For later, SD, DD, and CD stages:

“Unit-rate cost estimating” . . . early-on in the unit-rate method (SD), we know enough about the building’s size to use estimates based on cost per square foot or per cubic foot measurements Then later, as we know more about the project (CD), our estimates will tally detailed units like “number of pipe bends” and “linear feet of conduit” and “estimated cost of labor to install 50,000 sf of EPDM roofing membrane.”

Question 122

Roof safety railing: What height minimum?

Answer 122

42 inches minimum for rooftop safety railings.

Permanent and temporary railing systems available. Railings required anytime work happens on the roof. May penetrate the roof or parapet. . . or may sit on top of the roof, non-penetrating, with weights (like this)

Mechanical equipment screens, in most cases, are limited to no more than 18 feet above the roof surface.

Question 123

An architect is looking to reduce the cost of ductwork in an open-plan office. Which is a viable approach?

Economizer

Geothermal

Plenum

Dual-duct

Answer 123

A: Plenum

To reduce the cost and building volume associated with return air ductwork, in open-plan offices we often run a single large return air duct into the “plenum” space above the dropped ceiling and below the structural deck. If a duct is analogous to a stream, a plenum is analogous to a lake. The entirety of the plenum is then suctioned so that a return grille can be placed anywhere in the grid and suck air back to the AHU through the plenum. See an example here. Or a video here.

In “displacement ventilation” systems, we also use a plenum for supply air. See here.

Question 124

How many water closets are required for the women’s room of a 15,000 GSF one-floor office building with an occupancy load of one person per 150 GSF?

Answer 124

A: 2 water closets for the women’s restroom

15,000 GSF/1 person per 150 GSF = an occupant load of 100 people. BUT only half of them are women, so we have 50 women to serve. Don’t forget to divide by two on the exam!

Business classifications require one water closet per 25 for the first 50 occupants, so we need two water closets in the women’s room.

The common use of English terms in plumbing fixtures don’t align with plumbing trade jargon. A “lavatory” means a non-kitchen sink. . . like a small sink in a bathroom for handwashing. A “water closet” in this code table means a toilet (or sometimes a urinal. . . sussing that out requires more code reading). In this example, the table told us that we need two toilets in the women’s room. To confuse you further, a women’s restroom—the whole room—may be noted on a floor plan, among other titles, as “toilet,” “toilet room,” “water closet,” or “lavatory.”

Question 125

At its most shallow, the roof slopes such that it drops 4 inches over a 16’-8” horizontal run. The slope of the roof, at its most shallow, is _______ degrees. Round up or down to the nearest whole number. Use the NCARB demonstration exam’s calculator for practice (click here and then select the ARE 5.0 Demonstration Exam on the right-hand column.)

Answer 125

A:1 degree

Explanation

At its most shallow, the roof slopes such that it drops 4 inches over 16’-8” . . .

16’-8” = 200 inches

4 inches / 200 inches = rise over run

SOH CAH TOA: tan (theta) = 4 / 200

tan (theta) = 0.02

when you open the calculator, it will default to radians. . . be SURE to switch from rad to deg!

you’ll enter this into the exam’s calculator by first inputting 0.02 and then pressing atan

atan 0.02 = (theta)

(theta) = 1.15 degrees

Being able to seamlessly move between degrees, percentages, and ratios will net you at least three extra correct questions on PA and PPD. Take a moment now to convert the slope in this problem to percentage, then to a ratio. . . scroll down far to see the answer.

Question 126

What is a one-way solid slab with bearing walls?

Answer 126

Pros: least expensive; cons: can’t span far, can’t handle much load; uses: apartments/hotels containing small uniformly-arranged rooms with many bearing wall opportunities and light residential loading.

Question 127

What is a one-way solid slab with beams concrete system?

Answer 127

Pros: longer spans, and higher loads; cons: more expensive, increased floor-to-floor height requirement, beams interrupt duct runs; uses: heavily-loaded industrial buildings with large open-plan wall-less rooms. Click here.

Question 128

What is a one-way solid slab with beams and girders concrete system?

Answer 128

Higher-still loads, spans, floor-to-floor height requirements, and expense because of formwork.

Question 129

What is a One-way solid slab with slab bands concrete system?

Answer 129

Like the previous two flavors, slab bands support high loads but unlike those, they do so with less floor-to-floor height requirement and less formwork, and may even require less concrete (because the slab needn’t span as far between beams). The beam is kind of “on its side” and flat instead of vertical.

Question 130

What is a One-way concrete joist concrete system?

Answer 130

Like one-way beams conceptually, but many smaller joists instead of a few medium-sized beams. Also called a “ribbed slab,” this system reuses metal pans for formwork. As an alternative in medium-loading applications, we can skip every-other joist (click <>). While these are similar to the others structurally, we build them inside-out: instead of using custom formwork to bump down horizontal structural elements, we use off-the-shelf formwork that comes in standard sizes to carve out—to subtract—the slab-only spaces between horizontal joist elements. To see how these are built click here.

Question 131

What is a Two-way flat plate concrete system?

Answer 131

Just columns supporting a floor-ceiling concrete plane. Pros: inexpensive (no extra beam formwork), low floor-to-floor height requirements, and flexible for design because columns can be moved a bit one way or the other so they don’t land in the middle of a corridor; cons: can’t handle high loads and not great with seismic lateral loads because the connection between the column and floor is so flimsy; uses: VERY popular for apartments and hotels.

Question 132

What is a two-way flat slab concrete system?

Answer 132

A slightly more complicated, slightly more expensive, and much-better-at-resisting-lateral-forces version of the flat plate system with a beefier connection where the column meets the slab.

Question 133

What is a two-way slab and beam concrete system?

Answer 133

Beams move in both the X and Y dimensions. Heavy loads, used with a square column grid, high floor-to-floor height required, expensive because of extra formwork.

In the image below, we see a two-way slab and beam concrete system on the left and a one-way solid slab with beams and girders system in the rest of the ceiling.

Question 134

What is a waffle slab system?

Answer 134

A two way grid. Expensive, lots of re-usable off-the-shelf, subtractive, metal-pan formwork, capable of carrying large loads, and popular 75 or 50 years ago. Click here to see what they look like.

Question 135

Lifecycle cost analysis: what phase of design?

Answer 135

A: Best answer is DD, especially on the exam. For instance, curtain wall systems, photovoltaics, mechanical systems, exterior finish materials, and many other commonly life-cycle-cost analyzed alternatives–generally materials and systems– get fleshed out in DD. . . .but, know for your career, depending on the alternatives we’re comparing, LCCA could be involved in planning/programming, SD, or CD too. That’s because less commonly we may need to analyze sites to purchase factoring in not only purchase price but also account for tax rates and long-term government subsidies for building in a brownfield or economic development zone (planning); or we may need to compare alternative initial and long-term costs associated with two different fasteners, one that offers low purchase price and another that offers longevity (CD).

Lifecycle cost analysis: Tells us things like which chiller is really cheaper . . . in the LONG term? LCCA means accounting for the cost of not only purchasing and installing a system or material, but also the (inflation-adjusted) cost of running it, powering it, maintaining it, and salvaging it.

Question 136

List the advantages and disadvantages of packaged terminal air conditioners (PTACs)

List the advantages and disadvantages of mini splits

List the advantages and disadvantages of fan coil units

Answer 136

Remember that the compression-refrigeration cycle makes the coolth, and that a separate system of fans and pumps move coolth around. Each of these three systems looks like a box, so folks often get confused between them, but the technology inside them varies considerably.

PTACs are essentially window units that are set into the exterior wall instead of the window. You’ve seen them in hotels, apartments, and hospitals. They look like this. They’re self-contained because they have their own compression-refrigeration cycle and don’t rely on a remote chiller and pumped chilled water.

Advantages: Inexpensive, no ducts needed, super-easy to install (no trained HVAC professional needed) high level of thermal control (I can have mine on heat and you can have yours on cooling and someone else can have their’s off)

Disadvantages: Very noisy (fan and compressor in the room), ugly (visible both inside and outside), inefficient (all those separate compressors, each one only serving one room!), and that’s a lot of compressors to run and maintain over time.

Mini splits: smart split-system A/C with one outdoor unit connected to one to five indoor units, so one indoor unit for each thermal zone. You’ve seen them too, but primarily in newer buildings and newer renovations. They look like this. Each indoor unit–and the outdoor unit–can serve as the condenser (high-pressure refrigerant, hot) or the evaporator (low-pressure refrigerant, cold), so each indoor unit can heat or cool through variable refrigerant flow (VRF) technology. Think of an old-time telephone operator patching through calls. . . . VRF technology works like that, moving refrigerant to zones where heating is needed (high-pressure, hot) and moving refrigerant away from where cooling is needed (low-pressure, cold). Heat can then be moved from inside to outside, from outside to inside, or from room to room.

Advantages: no ducts needed (just refrigerant pipes connect the units), can heat and cool different rooms simultaneously (because each unit can be hot or cold), efficient, the noisy compressor is in the outdoor unit and the indoor fans are quiet (more because someone prioritized quiet in their design and branded them as such than anything inherent in this specific technology. . .there’s no reason that fan coil units couldn’t be just as quiet as mini splits, it’s just that no one expects them to be so they aren’t).

Disadvantages: More expensive and more complicated to install than PTACs (but the price keeps coming down), needs a spot outside the building for that outdoor unit, and if you have 500 dorm rooms to cool, you’d need 100 of those outdoor units. . . so these systems don’t scale well to very large buildings. It may be difficult to get fresh air into the building through this system necessitating a separate fresh air system.

Fan coil unit: a remote chiller–on the roof, in the basement, or in some nearby building–makes chilled water and pumps it around to all the thermal zones. A remote boiler–on the roof, in the basement, or in some nearby building–makes hot water and pumps it around to all the thermal zones. Each thermal zone has a fan coil unit (FCU), which looks like this, sits in the ceiling connected to ducts, in a closet connected to ducts, or as a box in the room without ducts; each fan coil unit includes a chilled water coil and a hot water coil and a dumb fan that blows room air over one coil or the other when the thermostat tells the fan that the room is too hot or too cold. If it’s a big residential building, hotel, hospital, etc. with different simultaneous heating and cooling needs, lot’s of thermostats, there’s a good way to get fresh air into each room, and you don’t see grilles from PTACs on the outside under each window, there’s a good chance each dwelling has fan coil units. . . likewise for spaces in large non-residential buildings–like a server room or storeroom–where fan noise isn’t a problem and fresh air for occupants isn’t important. In other occupied and noise-sensitive areas of large non-residential buildings, we’ll typically install remote ducted air handling units that bring coolth and fresh air down the corridors, then branch into office suites where one thermostat may control 10 rooms. People are grudgingly willing to give up control of their room’s thermostat at work. . . but folks get weird when you take away their thermal control at home.

Below is a photo I took of an exceptionally simple fan coil unit. Hot water moves through the pipe and when the thermostat reads that the room is too cold, the valve in the pipe opens up, hot water moves through the coil, and the fan blows air across the coil.

FCU Advantages: no visible ugly grilles on the facade and no ugly outdoor equipment (other than a remote cooling tower for the remote chiller), no ducts needed (just hot and cold water pipes connected to a remote mechanical room), can heat and cool different rooms simultaneously (because each unit can blow over the hot or cold coil), efficient (because FCUs rely on large central equipment), quieter than PTACs (but noisier than mini splits when there are boxes in the room,…though they wouldn’t have to be noisy if some company put some R+D into quieting the fans the way that the mini split manufacturers have). Relatively noisy FCUs may be just as quiet as mini splits with long duct runs between the fan and the room (but I don’t think that NCARB knows that because that’s not in any of the books they use). These are scalable and make the most sense for large buildings. Only one compressor to maintain for the whole building, located at the central chiller.

Disadvantages: More expensive and more complicated to install than PTACs (lots of piping), each zone needs fresh air from somewhere, so we’ll need to duct that in with a separate system or open a window.

Question 137

A ten-story building is built with a story drift factor of 0.01 and a story height of 12’. The door on the bottom floor has a maximum displacement of 1/4 inch before it gets jammed. How high can that door be?

Answer 137

Those who live in earthquake-prone regions know to scurry under a table when the earth starts to shake; but those who manage a restaurant, retail store, or funeral home know to prop the egress door open with a chair when they feel the tremors.

Story drift is the side-sway displacement of one floor’s facade, relative to the one below it, as a percentage of floor-to-floor height, in the event of an earthquake. Under seismic activity, the lateral forces pushing to the right will translate to a leaning (displacement) of the whole right-side building facade to the right. In our case, for every foot of height, the building’s facade will lean over 0.01 feet. For every story of height, the facade might displace 12 feet * 0.01 = 0.12 feet (or more than an inch from the bottom of the floor to the top of the ceiling). A ten-story building times 12 feet per story gives us a 120-foot tall building. At a story drift factor of 0.01 times 120 feet tall, the top of our building could lean 0.01 * 120 = 1.2 feet! If it’s a tall building, and the buildings are packed tightly on the street, the top of our tall building could collide with the tall building next to it in an earthquake! This means that, depending on how earthquake-prone the building’s location, the facade will need to be stiff enough–and/or the building will need to be sufficiently far away from its neighbor–so that it doesn’t touch its neighbor. See this table that relates the maximum allowable drift to facade construction type and “seismic use group.” (This rates the building’s life-saftey importance in an earthquake so an agricultural shed is Seismic Use Group I, a retail store is Group II, an elementary school is Group III, and a hospital is Group IV).

A steel frame with only moment connections will have a higher story drift factor than one with cross-bracing. A story drift factor of 0.02 is serious; a story drift factor of 0.06 will bring about building damage, and a story drift factor of 0.10 will likely topple the building.

Dealing with story drift factor might necessitate shoring interior non-load-bearing partitions so they don’t topple, or expanding the gap of seismic joints in building facades to the point where filling the joints against weather infiltration becomes difficult. Below is an example of one of those large seismic joints that must be filled (they can reach a total width of two feet!). Architects on the west coast sarcastically refer to these as “beauty caps” and do their best to visually integrate them into a building’s facade.

Besides colliding with a neighbor’s building, we also fear that a building’s exterior facade will shift enough to misalign the doors and jamb them shut just when occupants need to flee a collapsing building in an earthquake. Egress doors, doors to exit stairs, and revolving doors are of particular concern and that is the topic at hand in this example. Here, we know that the door can displace no more than 1/4-inch and still swing, so how high can the door extend and still displace small enough laterally so that it still swings open in an earthquake?

First, convert 1/4 inch to feet

1/4 * 1/12 = 0.0208 feet for our allowable maximum lateral offset to ensure that we can escape when the facade drifts.

0.01 * h = 0.0208

h = 0.0208 / 0.01 = a maximum height of about 2 feet tall

What does that mean? It means we have a problem because if our door is more than two feet tall, it may stick shut in an earthquake. We better find another door with greater tolerances, another way of detailing our door to allow for greater tolerances, or we better make our facade much more robust so it doesn’t sway (drift) as much. . . because we have no use for a 2-foot-tall egress door leading out of our building.

Note that neither the total height of the building nor the floor-to-floor height was relevant to solve this problem.

Question 138

Closed-cell rigid insulation (extruded polystyrene (XPS), expanded polystyrene (EPS), polyisocyanurate, and spray foam) uses tiny bubbles inside the insulation to create the thermal resistance. Each bubble of air in the cross-section of the board adds some tiny amount of additional R-value. The theoretical maximum R-value for tiny bubbles of air is 5.6. Why then do some manufacturers report foamed insulation values of greater than R-5.6?

Answer 138

A: The insulation from those manufacturers doesn’t use air, but rather another less-thermally-conductive gas, to fill the bubbles!

The problem with an architect using these higher-R-value values in her thermal modeling calculations: over time, and especially with either high or low outside temperatures, the high-R-value gases trapped in the tiny bubbles leaks out and is replaced by lower-R-value air. As a building with three of these four types of insulation ages, then, its thermal performance wanes because of the “leaking out” of the high-performance gases and the “leaking in” of the air. (The fourth type of insulation, expanded polystyrene (EPS)–the white rigid insulation–doesn’t shed R-value as it ages because it uses air instead of low-R-value gas to fill the bubbles from the beginning, which is part of the reason EPS is reported to have a bit lower R-value per inch than the others.)

This process–of time and temperature deteriorating the performance of closed-cell insulation because the air replaces the insulative gasses inside the cells–is called thermal drift.

We don’t know that much about thermal drift. Exactly how much of the insulations potency is lost, and after how many years is it lost?. . . but emerging research suggests that the deterioration happens rather quickly so maybe we shouldn’t be using the higher-R-value numbers in our calculations at all, especially in cold and hot climates (where insulation matters more in our models).

Question 139

Which has the highest embodied energy as measured in MJ/kg?

Aluminum

Concrete

Steel

Answer 139

A: Aluminum

Note the units. We are asking for embodied energy in megaJoule per KILOGRAM. Besides requiring a lot of energy to mine and process, aluminum is very light. In that unit, the order of the three materials is:

Aluminum 150 MJ/kg

Steel 20 MJ/kg

Concrete 1 MJ/kg

Optional reading: In about 2015 NCARB was spooked by how little “sustainability” content these exams had, so they added what they thought was sustainability content in haste, over-relying on materials discussions that is easily greenwashed. It’s so rare that you are debating between aluminum and concrete, and if you were, it is stupid to compare the two by weight. If you were deciding upon a cladding, and narrowed it to aluminum and precast concrete, you’d want to note that precast concrete is about 35 times as heavy as aluminum. Even after accounting for weight, then, the precast seems to have a lower embodied energy. But more importantly, as concrete cures, it releases CO2–insane amounts of CO2–into the atmosphere. This isn’t picked up in many embodied energy measurements. My back-of-envelope of equivalent CARBON per kg has precast concrete cladding and aluminum on par with one another. I don’t think NCARB knows about this yet, so stick with aluminum on the exam if you were asked something like this.

Question 140

What is a rigid frame?

Answer 140

Horizontal beams and vertical columns work together as a single unit. To resist wind, must be stabilized with stiff infill material.

To see an example, click here

Question 141

Describe the following IBC construction types:

Type I A; Type I B

Type II A; Type II B

Type III A; Type III B

Type IV

Type V A; Type V B

Answer 141

You likely won’t have to memorize these (they’ll be given in a code excerpt as part of the case study). . . but it’s good to be familiar with the concepts. . .

When reading the list below, know that by fire-rating, we’re often talking about wrapping the building’s structural elements in gypsum board or spray-on fireproofing; A=additional wrapping of the structure and B=no (or less) additional wrapping of the structure, so the structure in B often has a fire rating based only on the material itself without additional protection from gypsum board or spray-on fireproofing.

Type I: Noncombustible building elements. IA=3-hour fire rating and IB=2-hour fire rating

Type II: Also noncombustible building elements: IIA=1-hour fire rating and IIB=no additional fire rating

Type III: Exterior walls noncombustible. IIIA=2-hour fire rating on exterior walls and 1-hour fire rating on the rest and IIIB=2-hour fire rating on exterior walls and no fire rating on the rest

Type IV: Heavy timber (but you already knew that)

Type V: Any materials allow by code (typically Type V shows up as a stick-built structure). VA=1’hour fire rating on exterior walls and VB=no fire rating required

Question 142

What occupancy are courtyards (or roof terraces)?

Answer 142

More than 75 people and more than 25 feet above (or below grade)? Assembly (A-5)

More than 200 people and at grade? Assembly (A-5)

Fewer than 75 people high in the air or fewer than 200 at grade? Business (B)

The terrace or courtyard or other “enclosed” hard-to-egress outdoor space, then has to meet all the requirements of those occupancy groups.

* These kinds of things shouldn’t be memorized, but they’re good to understand and have a familiarity with in case you have trouble finding them quickly in case study reference materials.

Question 143

What type of flooring finish material works best with under-floor radiant heat? What type works worst with under-floor radiant heat?

Answer 143

Best floors for radiant heat: Stone and ceramic tiles

Not bad, but not great: Carpet (provided the carpet + pad is not too insulative), vinyl (but the heat can’t be too hot)

Not good: hardwood (warping and gapping from expansion/contraction as the floor is heated, then not-so-much heated, every few hours throughout the winter.

Engineered wood does better than hardwood, and laminate may do okay, but it depends on the particular product. In general, check with the manufacturer before specifying any finished flooring material if radiant heat will be used.

Question 144

Where do you put a parking lot entrance? Where do you put a parking lot exit?

Answer 144

A: The entrance goes on the major street and the exit goes on the minor street

It’s most efficient to separate the entrance and exit and prioritize the moving inbound traffic from the roadway to the building. Above all, we don’t want to back up traffic on the public road as cars wait to enter our parking lot.

We’ll put the exit discharge farther away from the building, on the low-volume, low-speed secondary road because exiting traffic tends to move more slowly. If a traffic backup or queue needs to form somewhere, better that it form inside the parking lot as cars exit, rather than on a public roadway as cars enter.

Of course, we’d never want a lot entrance or exit very close to an intersection of two roads.

Question 145

Watch this outstanding animated six-minute video.

Answer 145

https://www.youtube.com/watch?v=CZw9VtR0wS8

Question 146

Pipes. . . ABS, PVC, PEX or Copper?

Answer 146

ABS, PVC, PEX or Copper?

Memorize this one phrase for the exam: Plastic piping has less friction (good), but more thermal expansion (bad)

ABS (a type of plastic): Easy to install, inexpensive, low friction, no erosion of pipe over time. . . Drain, waste, and vent use only (not for supply water, only for wastewater under very low pressure).

PVC (another type of plastic): used for irrigation supply or wastewater, no rust or metal deterioration. . . Can’t be used with hot water, not rated for drinking water because it can’t handle UV, high temperatures, or high pressures.

CPVC: A type of PVC that CAN be used for hot water and drinking water. It’s rigid, white, and looks like this.

PEX (another type of plastic): easy to install and inexpensive, low friction, no erosion of metal pipes . . . some grades of PEX are more durable than others. It’s flexible, blue (for cold) and red (for hot), and looks like this.

Copper: ductile (so can be bent around corners without the need for elbow joint fittings), can handle higher pressure than palstic, and unlike plastic, you can leave copper exposed outdoors without UV breakdown. . . but expensive, labor-intensive to install, and hard water can cause deterioration. Because it can handle higher pressures, copper is used for many large-building applications.

How to decide between PEX and CPVC for supply water applications? Their advantages vary based on your tolerance for water hammer (both are good but PEX is better), whether you have to snake your pipe between tight spaces without drilling holes in studs (PEX is better), your water flow noise tolerance (both are good but PEX is better), the likelihood of nasty organic growth in the pipe (CPVC is better), the likelihood that someone will bump into an exposed pipe with a box they are carrying (CPVC is better), the maximum water temperature (CPVC is better), the amount of chlorine in your municipal system (CPVC is better), UV exposure (both are bad, but CPVC is better). . . I don’t think this is worth memorizing the relative advantages of these two, but it’s good to be familiar with them so you can recognize them when needed.

*You may think that this is a PDD question more than a PPD question, but there’s LOTS of questions on this level of detail in PPD.

Question 147

How do you design a blast-resistant building? Take a moment to guess the answers aloud. . . . the answers are exactly what you’d guess if you think about it for a minute.

Answer 147

It’s not the blast’s concussive wave, nor the “primary fragments” of the bomb casing. . . but rather the “secondary fragments” of the shattering shards of flying building materials that kill and mame the most in a blast event. How to protect your building? Keep the bomb far away, hold the skin together, and avoid progressive structural collapse

1. Increase the “standoff distance” so that a van with a bomb can’t get close to the building. This is both the most obvious and the most effective. . . but is not always possible.
2. Concrete: specify extra rebar reinforcing (click here) to secure the concrete building envelope and structure
3. Steel: specify building assemblies with multiple tough-but-bendy layers. For instance, steel studs with thin-gauge sheet steel on each side of the stud with meshed cement board and extra lateral bracing between the studs. This bend-but-don’t-break strategy should be ductile, stable, and structurally redundant. Click here.
4. Specify blast-resistant glazing: plastic interlayer holds onto the glass shards in a laminated window
5. Avoid masonry (too many small fragments that can become projectiles)
6. Recognize that you can’t plan for every possible blast; and even if you could, you can’t make the building totally blast-proof

It’s not just bombs from the outside we’re worried about. Petrochemical plants, munitions plants, and any building storing explosive materials inside may be a more common spark (pun intended) for a blast-resistant building (BRB).

Question 148

Which increases cooling loads more on the HVAC system: uplights that illuminate ceiling or downlights that illuminate the occupants? Try to answer yourself before flipping these cards! It’s important in developing long-term recall.

Answer 148

The answer: Probably the uplights increase the cooling load on the mechanical system because we’ll need more light reflected off the ceiling to get the required light levels at the desk. . .

If the goal is to keep the foot-candles constant (light received at the desk), then the uplight will require more lumens because some light will be lost to the ceiling before reflecting back down and reaching the desk. We’ll then need more watts for lighting and thus introduce more heat from the up-lights than from downlights. . . and the air conditioner will have to eliminate more BTUs just to keep up.

Read on only if you want to geek-out. . .

A subtle caveat (that I’m not sure NCARB is sophisticated enough to pick up on): If, however, the downlights are incandescent, you could imagine that occupants, baking under the “heat lamps” directed at their skin would need to set the thermostat to a lower temperature just to keep comfortable. In other words, you and I could both be in a 75-degree room, but if an incandescent or halogen light is shining on you, but I was in a room where the same incandescent lumens were directed at the ceiling, you’d likely feel warmer than I do and need to set the thermostat at 70, increasing the load on the HVAC system. Plus downlights shine in occupants’ eyes, and with their attendant glare issues, may make the room appear darker than measured by a light meter.