PROJECT PLANNING + DESIGN

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

Right hand reverse bevel: Hinge on right opens outward
Left hand Reverse bevel: hinge on left opens outward
right hand: hinge on right opens inward
left hand: hinge on left opens inward

Question 4

How can we shade windows?
North?
South?
East/West?

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

Can cause extreme deformation to the columns below the shear wall, as they don’t resist the shear forces.

Question 12

What is the “soft story” problem?

Answer 12

a. flexible first floor
b. discontinuity: indirect load path
c. heavy super structure

Question 13

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

Answer 13

the “soft story” allows for building drift and collapse

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. solutions: add more columns, add bracing, add external bracing.

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..

Question 17

If our goal is to shade the windows, which illustrates the west side of the building?
a-vertical shades b-horizontal shades

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

Are wind loads higher at the top of tall buildings?

Answer 19

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 20

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 20

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 21

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 21

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 22

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 22

Which type of soil is more stable to build on?

Clay

or

Sand

Question 23

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

Absorptive

Or

Airtight

Answer 23

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 24

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

Longer

or

Shorter

Answer 24

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 25

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

Sound-reflective

or

Sound-absorptiv

Answer 25

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 26

What is an overturning moment

Answer 26

rotational force such as that found in a retaining wall.

Question 27

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 27

Answer: 2.2 Kips at 63° from horizontal

Question 28

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 28

Answer: insulation

Question 29

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 29

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 30

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 30

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 31

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

Answer 31

Answer: 18amps

Standard voltage is 120 volts.

Question 32

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 32

Answer: Size the wire

Question 33

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

Answer 33

Answer: Add approximately 730 sf of absorbing material

Question 34

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 34

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

Question 35

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

Above

or

The side

Answer 35

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 36

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 36

Answer: 113fc

Question 37

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 37

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

Question 38

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 38

Answer: 85 horizontal footcandles

Question 39

Vierendeel Truss

Answer 39

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.

Question 40

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

Answer 40

Raceways: through the structure, through the concrete topping, through the wall, from the ceiling, suspended along trays.

Question 41

How do we bury conduit into concrete structure?

Answer 41

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 42

Underfloor raceway ducts

Answer 42

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 43

Floor cellular raceway systems

Answer 43

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 44

Poke-through floor boxes vs floor cellular raceways

Answer 44

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 45

Under-carpet wiring system

Answer 45

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 46

Surface metal raceways

Answer 46

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 47

Ceiling raceways

Answer 47

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 48

Raised access flooring system

Answer 48

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 49

Floor-to-ceiling raceway poles

Answer 49

These hanging receptacles offer another from-the-ceiling option.

Question 50

Locate the portions of the section most susceptible to thermal bridging

Answer 50

Overhangs, balconies, door and window perimeters

through uninsulated slab

Question 51

Locate the portions of the section most susceptible to air infiltration

Answer 51

roof overhangs, balconies and window/door perimeters

Question 52

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

Thermal bridging across rafters melts the snow first

Answer 52

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

This double stud door frame provides a “thermal break,” a way to separate the structure of the inside and the outside of the door into two different planes, separated by an insulated space.

Question 53

Bracing types

Answer 53

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

Question 54

What is the area-weighted U-value of this wall
80% @ R-20
20% @ R-1

Answer 54

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= 0.0580% + 120%=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?

Question 55

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 55

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 56

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 56

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=1.74+1.05+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 57

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 57

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.

Question 58

Put these in order from most effective insulation to least effective insulation:
Air in Cavity
Perlite/Vermiculite in cavity
Grout in cavity

Answer 58

Answer:

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 59

Put these in order from highest sound transmission loss (TL and STC) to lowest sound transmission loss
Air in Cavity
Perlite/Vermiculite in cavity
Grout in cavity

Answer 59

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 60

Where should I locate a “vapor barrier?”

Answer 60

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

1. Keep out rain: rain control layers
2. Keep out outdoor air: air control layer
3. Keep out cold/heat: thermal control layer
4. 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 61

Condenser

Answer 61

pump that circulates refrigerant

Question 62

Compressor

Answer 62

high-pressure hot refrigerant

Question 63

Evaporator

Answer 63

low pressure cold refrigerant

Question 64

Air-to-air system

Answer 64

fan over condenser and evaporator

Question 65

Air-to-water system

Answer 65

fan over condenser, pumped water over evaporator

Question 66

Water-to-Air system

Answer 66

pumped water over the condenser, air over the evaporator

Question 67

Water-to-water system

Answer 67

pumped water over the condenser and a different pumped water system over the evaporator

Question 68

Split system

Answer 68

condenser outside, evaporator inside (residential)

Question 69

Minisplit

Answer 69

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

Question 70

Swamp cooler

Answer 70

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

Question 71

Evaporative cool tower

Answer 71

uses evaporation of water for cooling, no fan, for very dry climates only

Question 72

Cooling tower

Answer 72

for cooling condenser water by blowing outside air over it

Question 73

Chiller

Answer 73

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)

Question 74

Air-handling unit

Answer 74

located down the hall, cools air for delivery to the room via ductwork

Question 75

Fan coil unit

Answer 75

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

Question 76

Direct expansion (DX

Answer 76

like a window unit; with all cooling components including refrigeration machine and fan in one box

Question 77

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

Answer 77

how much control over the rate of flow. Variable generally offers more comfort control and more energy-efficiency, but more complex equipment

Question 78

Geothermal system

Answer 78

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

Question 79

Chilled beams

Answer 79

like radiators for coolth; measures are required to prevent condensation

Question 80

Why are lab buildings big energy hogs?

Answer 80

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 81

What building type is most associated with chilled beam technology?

Answer 81

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 82

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

Answer 82

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 83

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 83

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.

Question 84

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. 2,000 square feet of the 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 84

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 85

Types of security systems. . . .

Answer 85

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 86

Displacement ventilation

Answer 86

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 87

When do architects use a Faraday cage?

Answer 87

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

Question 88

Embodied energy

Answer 88

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).
The take-away: Note the high embodied energy of petroleum-based products (carpet and vinyl). Linoleum seems like it would be a petroleum product, but is instead made with organic materials: sawdust, jute, and linseed

Question 89

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

Answer 89

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.
The takeaway: Everyone seems to forget about the weight! Intentionally misleading manufacturer’s literature compounds this problem

Question 90

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

Answer 90

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 91

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

Answer 91

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 92

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

Answer 92

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 93

What are the takeaways from this graph:

Answer 93

Materials that involve mining or petroleum (including plastics)–and those with complicated industrial processes–require more energy to produce. Organic options (wood, cellulose insulation, linoleum, wax), simpler processes, and recycled content generally require less energy to produce.

Question 94

A ballroom dance floor measures 24 feet by 20 feet; what is its maximum occupant load?

Answer 94

A: 96 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, we find that we can calculate an occupancy load of 5 sf/occupant.

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

480sf / 5 sf per occupant = 96 occupants

Question 95

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 95

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.

Question 96

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 96

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 97

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 97

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.

Question 98

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 98

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

Question 99

Fire wall vs fire barrier vs fire partition

Answer 99

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 100

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

Answer 100

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 101

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

Answer 101

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 102

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

Answer 102

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.

Question 103

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 103

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 104

Should crawl spaces be ventilated or sealed?

Answer 104

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 105

vectors

Answer 105

correct vector arrows will meet tip to tail if rearranged

Question 106

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

Answer 106

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 107

What is automatic dimming?

Answer 107

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 108

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

Answer 108

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 109

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 109

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 110

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 110

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 111

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

Answer 111

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 112

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

Answer 112

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

Question 113

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 113

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 114

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 114

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 115

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 115

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

Question 116

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

Answer 116

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 117

What is an impact load?

Answer 117

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

Question 118

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 118

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 119

The problem with lights recessed in the ceiling:

Answer 119

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.

Question 120

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

Answer 120

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 121

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 121

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 122

Snow melted between rafters? vs Snow melted on top of rafters

Answer 122

Between: 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.
On top: 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.