Thermal & Moisture Flashcards
(83 cards)
<p>Human comfort range</p>
<p>comfort: 65-80 deg F</p>
<p>tolerance: 60-85 deg F</p>
<p>Target temp for IBC/IMB</p>
<p>68 deg F</p>
<p>Types of temperatures</p>
<p>dry bulb = just a thermometer</p>
<p>wet bulb = plus wet cloth, swung around, aka sling psychrometer</p>
<p>hygrometer sensor = electronically sense humidity</p>
<p>relative humidity = ratio of current:max, comfort is 30-65%, tolerable is 20-70%</p>
<p>more humidity at >85 deg F, feels v hot bc evaporative cooling is ineffective</p>
<p>Wind speed vs temp</p>
<p>greater wind speed, lower apparent temp bc of increased convection</p>
<p>Surface temps</p>
<p>changes apparent temp by engaging bodies in radiative heat transfer, v important in cold rooms</p>
<p>Black globe thermometer</p>
<p>detects air temp + emissive heat radiation from objects</p>
<p>can collect MRT, mean radiant temperature</p>
<p>Effective temperature</p>
<p>takes into account temp, humidity, air movement</p>
<p>Surface radiation measurements</p>
<p>viewed angle = how much of the hot/cold surface is viewable</p>
<p>emissivity = ability to absorb/emit heat</p>
<p>emittance = ratio of heat emitted by that obj:heat emitted by a black body</p>
<p>Types of ventilation</p>
<p>to unoccupied space:Âto prevent mold</p>
<p>to occupied spaces:Âto provide breathable air, remove noxious gases, moisture</p>
<p>natural ventilation: must have 4% of room's floor area equal to operable windows, or if an adjoining room is added, 8% of both room's floor area, not less than 25 sqft</p>
<p>mechanical ventilation: tables based on occupancy (not the same ones as for egress) determines air flow rates in cfm/sf (cubic foot minutes)</p>
<p>Comfort charts</p>
<p>combine temp, humidity, other factors for setting ventilation goals</p>
<p>if humidity is high, then temp needs to come down</p>
<p>if temp is down, then radiation needs to increase</p>
<p>psychrometric chart is best example</p>
<p>Psychrometric chart</p>
<p>warm air holds more moisture than cold air</p>
<p>vertical lines = dry bulb temp</p>
<p>lines sloping upper left/lower right = wet bulb temp</p>
<p>curved lines from lower left/upper right = relative humidity</p>
<p>100% humidity = saturation line/dew point line = wet bulb/dry bulb temps are the same</p>
<p>upper left side shows enthalpy = total amt of sensible and latent (water phase stored) heat</p>
<p>enthalpy is the total amt of heat that must be removed by HVAC systems</p>
<p>Heat loss calculations</p>
<p>thermal conductivity = k, the rate at which heat passes through 1 sq ft of a 1 in. thickness of a material when heat difference is 1 deg f</p>
<p>conductance = C, is the same, but with varying thicknesses</p>
<p>resistance = R, is the inverse of C</p>
<p>U value = overall heat transmission coefficient is sum of resistances, inverted</p>
<p>total heat loss, q = U*A*temp change</p>
<p>heat loss via air infiltration: q = Vol(1.08)*temp change, where 1.08 is specific heat of air, vol is volume of air flow</p>
<p>Â</p>
<p>Â</p>
<p>Latent vs. sensible heat</p>
<p>sensible = you can feel it</p>
<p>latent = stored in water phase changes</p>
<p>people produce both!</p>
<p>Dampproofing</p>
<p>controlling moistureÂthat is not under hydrostatic pressure</p>
<p>always applied on positive (wet) side</p>
<p>admixtures: to concrete, salts of fatty acids, mineral oil, powdered iron, can reduce concrete strength</p>
<p>bituminous coatings: asphalt or coal-tar pitch, hot or cold, won't work on cracks that appear later</p>
<p>cementitious coatings: portland cement mortar, with powdered iron, makes a smooth surface for coatings, but also dampproofs</p>
<p>membranes: hot or cold applied asphalt felts, butyl, polyvinyl chloride, etc., membranes, more costly, usu. for waterproofing</p>
<p>plastics: polyurethane or silicone coatings, for above grade dampproofing</p>
<p>Waterproofing</p>
<p>for controlling movement of water under hydrostatic pressure</p>
<p>positive side: wet side, applied after in place;Ânegative side: applied after element is in place, but on dry side; blind side: applied before pour</p>
<p>sheet membranes: built up layers of bituminous saturated felts or butyl, polyvinyl chloride, sometimes nailed, better if adhered</p>
<p>fluid-applied: asphalts, urethanes, all on positive side</p>
<p>cementitious: portland cement, sand, plus waterpoofing agent, eg, metal oxides, positive side best, can do negative side as backup</p>
<p>bentonite system: bentonite clay in kraft paper packages or plastic liners in panel form, often combined w geotextiles, for both blind and positive sides</p>
<p>protect during backfilling w/ XPS or asphalt impregnated glass fiber mats</p>
<p>geotextile or drainage board to relieve hydrostatic pressure against wall insulation</p>
<p>crystalline waterproofing: concrete admixture or surface applied that fills pores and cracks, and contintues whenever water is added, so self-healing</p>
<p>Footing drainage</p>
<p>4" or 6" perf pipe layed just below basement slab, at footing</p>
<p>gravel that surrounds it separated from backfill by geotextile</p>
<p>sloped to a storm drain or sump pump, depending on water expected</p>
<p>positive slope away from bldg of at least .5"/ft for 6 ft</p>
<p>Waterstops</p>
<p>seal construction joints in concrete walls that will be waterproofed</p>
<p>rubber or neoprene strips, ribbed or dumbell shaped</p>
<p>half goes in first half of pour, second half in second pour</p>
<p>Weather barrier design considerations</p>
<p>climatic zone, microclimate, indoor environment, type of structure, type of cladding, expected bldg movement, cost, desired appearance, security, acoustics, fire resistance, durability</p>
<p>Water barriers</p>
<p>ext. surfaces of walls, roofing, membranes within walls, below grade waterproofing, drips, flashing</p>
<p>should be a continuous exterior barrier, but joints, leaks, wind-driven rain, construction defects often let water through, so water must be allowed to exit</p>
<p>Rain screens</p>
<p>deal w weather at exterior surface, then, under an air cavity (so that pressure differentials aren't created), a vapor barrier and flashing prevents what little water makes it through from getting into structure</p>
<p>true = cladding stops water,Âpressure-equalized, vented, compartmentedÂair cavity behind cladding, with continuous air barrier behind it</p>
<p>drained = exterior cladding does not stop water when pressure differences arise, but allow water that gets in to drain out, ventilated air cavity allows this</p>
<p>air barrier always at drainage plane/back of air cavity</p>
<p>Vapor retarders</p>
<p>slows water vapor movement, increases insulation effectiveness</p>
<p>vapor pressure encourages warm, wet air into areas w drier, cooler air/surfaces, can cause condensation</p>
<p>vapor barriers most effective where warm, wet air should be prevented from migrating</p>
<p>can also be air barriers, if they're in the right location</p>
<p>made of polyethylene, aluminum foil, self adhering sheet membranes, fluid applied membranes</p>
<p>Permeance ratings</p>
<p>perm = 1 grain of moisture per hour per sq ft, per inch of mercury diff in pressure</p>
<p>less than 0.1 is impermeable (Class I), 0.1 to 1 is semi-impermeable (Class II), 1-10 is semi-permeable (Class III), 10+ is permeable</p>
<p>Vapor barrier placement</p>
<p>in very cold climates, place vapor-imperable barrierÂon warm side of insulation, inside, with a vapor-permeable air barrier on the cold side, outside, in case of weather moisture coming in</p>
<p>in very hot climates, vapor-impermeableÂplaced on warm side of insulation, outside, also acts as air barrier</p>
<p>in mixed climates, a vapor-permeable air barrier should be placed on the outside of the insulation, vapor passes freely</p>
<p>Climate zones & vapor barriers</p>
<p>1A,Â2A, 3A = hottest, humid</p>
<p>2B = hot, dry</p>
<p>3A, 4A = mixed, humid</p>
<p>3B, 4BÂ= mixed, dry</p>
<p>4C = cool, marine</p>
<p>5A, 6A = cool, humid</p>
<p>5B, 6B = cold, humid</p>
<p>7, 8 = very cold, sub-arctic</p>
<p>1,2,3,4: no Class I/IIvvapor barriers on inside of framed walls</p>
<p>marine 4, 5,6,7,8: Class I/II vapor barriers req on inside of framed walls</p>
<p>Class III only allow where wall assembly reqmts met</p>
<p>Â</p>
<p>Â</p>
Insulation on inside v outside of framing
inside = standard, but then vapor barrier subject to damage, leaks
outside = usu. double insulation (cavity gets filled any way), and vapor barrier can be protected by ext. insulation, must then use clips to not break insul./vapor barrier too often when attaching cladding
Detailing of weather barrier
air barrier continuous, supported, and sealed ab. windows (w/ SASM, eg)
air space should be 2", 1.5" min
cladding/structure cnxns have thermal breaks, and must be moisture proof
on interior side of insulation, limit air movement/ventilation
only one vapor barrier!
vinyl wall coverings or impermeable paints may accidentally act like a vapor barrier!
masonry, since absorptive, can conduct moisture, especially when heated (sun radiation, eg)
sill flashing must have turned up dam edges
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Ideal insulation
vacuum is best, but impossible
totally still air is next best, but also not possible
all insulation attempts to make small pocket of still air that aren't so big as to allow convection currents
Insulation types
loose fill: bits blown in, used where hard to reach, esp retrofits, bits of mineral wool (heavy), cellulose (heavy, compacts), cotton, fiberglass, perlite, vermiculite; all need vapor barrier or retarder
mineral wool: rock wool is melted basalt or other, and long fibers made from molten material, bound w chem agents; slag wool is from blast furnace slag, same method, is most common, since req 50% recovered material
cellulose: recycled paper plus fire retardant, binders can prevent settling, wet or dry applied (when wet, called sprayed fiber insulation, blow in blanket system or BIBS), very green, but concerns about dust
cotton: recycled clothing plus polyester for binding, and fire retardant, loose or in batts, slightly higher R-value
fiberglass: melted sand and glass, fibers collected, then binder used (no longer formaldehyde)
perlite: siliceous volcanic rock cooked to puff up, used under floating concrete floors and in hollow CMUs (and elsewhere in bldg materials)
vermiculite: hydrated laminar Mg-Al-Si, forms small wormlike pcs when heated to puff up, sometimes as asbestos, so careful
Batt insulation
glass fiber or mineral fiber faced w something
kraft paper, which can also be a vapor retarder
can have reflective surface, and/or flame resistant facings, esp for where it will be left exposed
Board insulation
organic (outdated) from wood, cane fiber, straw layered w bitumen, paper, foil, etc. but can't acheive high R-values as inorganics
blowing agents for inorganics were CFCs, then HCFCs, but now hydrocarbon or carbon dioxide (still bad?)
EPS expanded polystyrene: closed cell, aka beadboard, bc polystyrene (a petroleum product) in beads before heated/blown (no HCFCs) and formed in molds, comes in various densities, cells can abs moisture, so vapor retarder needed
XPS extruded polystyrene: closed cell, pellets mixed w chemical, then blown (right now w HCFC), forced through extruder, denser, more expensive than eps, better insulation, often used at roofs, slabs
polyisocyanurate: closed-cell, polyiso, starts as liquid components (from PET/plastic bottles), heated, catalyzed, blown (only hydrocarbon), then layered in lams between facing material or directly onto surfaces, very water abs., greener?
polyurethane: closed-cell, no HCFCs, high R-value, but very expensive
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Sprayed foam insulation
polyurethane or polyicynene in tanks, head mixes, expands in place, so very tight seals
spray polyurethane insulation can be liquid-applied, when makes open-cells, but no harmful gases used in blowing process, though lower R-value
cementitious foam insulation: Mg-O Cl cement, compresed air, expander in sprayer to use in cavities bc mold resistant, fireproof, non-toxic, no VOCs, high R-value
no spray foam can be exposed to interior bc of potential offgassing
Radiant barriers
thin sheet of reflective material, usu Al that bounces heat back, must vace a ventilated air space, even if just corrugations
must have reflectivity of .9 9 (out of 1) and emissivity of .1 (out of 1)
used freq in attics, if in hot climate, pointed up, if in cold, pointed down
if backed by insul, called reflective insulation
Insulated concrete forms
ICFs, blocks or panels of foam (XPS)Â used as forms for concrete, left in place
must eventually be covered by a fire-resistant surface, eg gypsum wallboard
freq used at foundations
Roof shingles
asphalt or fiberglass: felt, asphalt or fiberglass, mineral stabilizer, mineral granules in shingles layed over asphalt-impregnated roofing felt nailed to wood sheathing (2"-4" vert rise for low slope shingles, 4"-12" vert rise for regular)
wood: cedar usu, no.1 blue label is best, if hand split, called shakes, edges can't touch so moisture doesn't build up there, same asphalt felt underlay (min 4" vert rise slope)
Roofing tile
heavy, and can't do low slopes (min 4" vert rise)
slate: quarried stone is split, usu .25" thick, edges not touching, layed over asphalt felt over sheathing or concrete decking, attaced w copper or galvanzied nails through pre-punched holes, very $ but durable (100 yrs), v fireproof
clay tile: made from same clay as brick, many shapes (English, Spanish, Mission), layed over asphalt felt, prepunched holes, also $, durable, fire-proof
concrete tile: portland cement + fine aggregates, either flat or made to mimic slate, clay tiles, layed the same way, but less expensive
Sheet metal roofing
copper, galv. iron, Al, terneplate (coated steel, terne is alloy of Sn w/ Pb (old school) or Zn, SS, Sn, Zn
min slope is 3" rise per foot
need matching accessories: gutters, leaders, flashing, cleats, fasteners, etc. to prevent galvanic action
interlocking joints at panel edges must allow expansion/contraction, fabbed in field
if Sn is present, can't use asphalt underfelt, must use red rosin paper
standing seams are folded, cleated, fastened, parallel to slope; if needed, perpendicular seams/flat seams are folded, soldered
Preformed roof panelsÂ
can also be used as walls; fastened directly to structure
2 layers corrugated metal w insulation btwn
eges have corrugation overhang to allow lapping, interlocking and/or weather sealing (if butt joined only, then must be flashed, usu only at walls)
metal can be Al, galv. steel, porcelain enameled steel
often used in industrial settings
Built-up roofing
built-up roofing: several layers of bituminous-saturated roof felting cemented together w/ asphalt or coal-tar pitch over nailable or non-nailable roof deck, each layer cemented so that felt does not touch felt, 3-5 layers, overlaid w gravel or crushed slag to prevent UV degredation/weathering
inverted built-up is where insulation is on top of layers, keeps layers protected from expans/contr weathering, walking damage, etc.
minimum slope: 1/4" per foot, positive drainage, crickets for diversions around pockets, scuppers/overflow drains at parapets, all intersecion of planes flashed, no 90 deg angles (ease them), items projecting through have curbs and flashing
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Single-ply roofing
less labor intensive than built-up, fewer places for errors, less weather and movement damaged, becoming widespread
modified bitumens: 50 mils of reinforcing fabric impreg with chemical-modified bitumen (make it more elastic), layed over separator sheet, over decking, covered w gravel ballast to prevent UV degr.
thermoset plastics: heated only once (will char after that), EPDM: ethylene propylene diene monomer, resists weathering, heat, fatigue, but only comes in black, must be sealed at seams, usu adhered to decking, can been fastened, v common; CSPE: chlorosulfonated polyethylene, Hypalon, v weather resistant, comes in white, adhered, but not common bc thermoplastics
thermoplastics: heated and reheated, can be recycled; PVC: polyvinyl chloride, inexpensive, hearty, easy to install, looses flex over time, so KEE (ketone ethylene ester) added, seams are heat welded, can be adhered, loose w ballast, fastened, white/tan/gray, bad manuf. process; TPO: thermoplastic polyolefin, polypropylene + ethylene propylene, loose w ballast, adhered, fastened, multicolored
all often reinforced w polyester fibers or glass fibers to get more dimensional stability, tear strength, better puncture, wind resistance, lies flatter for easier seaming, req for adhered, fastened; non-reinforced are cheaper, move better, good for laid loose/ballast
Elastic liquid roofing
fluid applied chemicals: butyl, neoprene, hypalon, etc. good for complex shaped roofs, eg thin shell concrete domes, same as stuff used for below grade waterproofing
Flashing
directs water away from joints/seams, angles, low spots
often still allows movement of jt or seam
made of galv. steel, SS, Al, Cu, plastic, elastomers
Roof accessories
expansion jts (every 100-150 ft), copings, roof hatches, smoke vents (in case of fire in hazardous occupancies), other vents
sealants (low/intermediate/high performance is about max allowed movement), caulking (low perfomance, less movement); jts should not get too deep, especially the wider they get
EIFS
exterior insulation and finish system
wet-applied cementitious finish o/ rigid insulation board attached to sheathing
types of cementitious finishes:
Class PB (polymer based)Â uses expanded polystyrene insul, embedded fiberglass mesh supports acrylic polymer, sand, pigment, etc.
 Class PM (polymer modified) extruded polystyrene insul, reinforcing mesh, polymer, sand, pigment, but thicker, more portland cement finish, so they need control jts, more impact resistant, more water and heat transfer resistant
Class MB (mineral based) portland cement stucco as finish
1990s many lawsuits bc of flaws/failures leading to moisture infiltr., moved to rainscreen assembly
