Thermal & Moisture Flashcards
<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>
<p>Insulation on inside v outside of framing</p>
<p>inside = standard, but then vapor barrier subject to damage, leaks</p>
<p>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</p>
<p>Detailing of weather barrier</p>
<p>air barrier continuous, supported, and sealed ab. windows (w/ SASM, eg)</p>
<p>air space should be 2", 1.5" min</p>
<p>cladding/structure cnxns have thermal breaks, and must be moisture proof</p>
<p>on interior side of insulation, limit air movement/ventilation</p>
<p>only one vapor barrier!</p>
<p>vinyl wall coverings or impermeable paints may accidentally act like a vapor barrier!</p>
<p>masonry, since absorptive, can conduct moisture, especially when heated (sun radiation, eg)</p>
<p>sill flashing must have turned up dam edges</p>
<p>Â</p>
<p>Ideal insulation</p>
<p>vacuum is best, but impossible</p>
<p>totally still air is next best, but also not possible</p>
<p>all insulation attempts to make small pocket of still air that aren't so big as to allow convection currents</p>
<p>Insulation types</p>
<p>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</p>
<p>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</p>
<p>cellulose: recycled paper plus fire retardant, binders can prevent settling, wet or dry applied (when wet, called sprayed fiber insulation, blow in blanket systemÂor BIBS), very green, but concerns about dust</p>
<p>cotton: recycled clothing plus polyester for binding, and fire retardant, loose or in batts, slightly higher R-value</p>
<p>fiberglass: melted sand and glass, fibers collected, then binder used (no longer formaldehyde)</p>
<p>perlite: siliceous volcanic rock cooked to puff up, used under floating concrete floors and in hollow CMUs (and elsewhere in bldg materials)</p>
<p>vermiculite: hydrated laminar Mg-Al-Si, forms small wormlike pcs when heated to puff up, sometimes as asbestos, so careful</p>
<p>Batt insulation</p>
<p>glass fiber or mineral fiber faced w something</p>
<p>kraft paper, which can also be a vapor retarder</p>
<p>can have reflective surface, and/or flame resistant facings, esp for where it will be left exposed</p>
<p>Board insulation</p>
<p>organic (outdated) from wood, cane fiber, straw layered w bitumen, paper, foil, etc. but can't acheive high R-values as inorganics</p>
<p>blowing agents for inorganics were CFCs, then HCFCs, but now hydrocarbon or carbon dioxide (still bad?)</p>
<p>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</p>
<p>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</p>
<p>polyisocyanurate: closed-cell,Âpolyiso, 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?</p>
<p>polyurethane: closed-cell, no HCFCs, high R-value, but very expensive</p>
<p>Â</p>
<p>Sprayed foam insulation</p>
<p>polyurethane or polyicynene in tanks, head mixes, expands in place, so very tight seals</p>
<p>spray polyurethane insulation can beÂliquid-applied, when makes open-cells, but no harmful gases used in blowing process, though lower R-value</p>
<p>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</p>
<p>no spray foam can be exposed to interior bc of potential offgassing</p>
<p>Radiant barriers</p>
<p>thin sheet of reflective material, usu Al that bounces heat back, must vace a ventilated air space, even if just corrugations</p>
<p>must have reflectivity of .9 9 (out of 1) and emissivity of .1 (out of 1)</p>
<p>used freq in attics, if in hot climate, pointed up, if in cold, pointed down</p>
<p>if backed by insul, called reflective insulation</p>
<p>Insulated concrete forms</p>
<p>ICFs, blocks or panels of foam (XPS)Âused as forms for concrete, left in place</p>
<p>must eventually be covered by a fire-resistant surface, eg gypsum wallboard</p>
<p>freq used at foundations</p>
