Moisture Protection & Thermal Insulation Flashcards
Dampproofing
controlling moisture that is not under hydrostatic pressure
always applied on positive (wet) side
admixtures: to concrete, salts of fatty acids, mineral oil, powdered iron, can reduce concrete strength
bituminous coatings: asphalt or coal-tar pitch, hot or cold, won’t work on cracks that appear later
cementitious coatings: portland cement mortar, with powdered iron, makes a smooth surface for coatings, but also dampproofs
membranes: hot or cold applied asphalt felts, butyl, polyvinyl chloride, etc., membranes, more costly, usu. for waterproofing
plastics: polyurethane or silicone coatings, for above grade dampproofing
Waterproofing
for controlling movement of water under hydrostatic pressure
positive side: wet side, applied after in place; negative side: applied after element is in place, but on dry side; blind side: applied before pour
sheet membranes: built up layers of bituminous saturated felts or butyl, polyvinyl chloride, sometimes nailed, better if adhered
fluid-applied: asphalts, urethanes, all on positive side
cementitious: portland cement, sand, plus waterpoofing agent, eg, metal oxides, positive side best, can do negative side as backup
bentonite system: bentonite clay in kraft paper packages or plastic liners in panel form, often combined w geotextiles, for both blind and positive sides
protect during backfilling w/ XPS or asphalt impregnated glass fiber mats
geotextile or drainage board to relieve hydrostatic pressure against wall insulation
crystalline waterproofing: concrete admixture or surface applied that fills pores and cracks, and contintues whenever water is added, so self-healing
Footing drainage
4” or 6” perf pipe layed just below basement slab, at footing
gravel that surrounds it separated from backfill by geotextile
sloped to a storm drain or sump pump, depending on water expected
positive slope away from bldg of at least .5”/ft for 6 ft
Waterstops
seal construction joints in concrete walls that will be waterproofed
rubber or neoprene strips, ribbed or dumbell shaped
half goes in first half of pour, second half in second pour
Weather barrier design considerations
climatic zone, microclimate, indoor environment, type of structure, type of cladding, expected bldg movement, cost, desired appearance, security, acoustics, fire resistance, durability
Water barriers
ext. surfaces of walls, roofing, membranes within walls, below grade waterproofing, drips, flashing
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
Rain screens
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
true = cladding stops water, pressure-equalized, vented, compartmented air cavity behind cladding, with continuous air barrier behind it
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
air barrier always at drainage plane/back of air cavity
Vapor retarders
slows water vapor movement, increases insulation effectiveness
vapor pressure encourages warm, wet air into areas w drier, cooler air/surfaces, can cause condensation
vapor barriers most effective where warm, wet air should be prevented from migrating
can also be air barriers, if they’re in the right location
made of polyethylene, aluminum foil, self adhering sheet membranes, fluid applied membranes
Permeance ratings
perm = 1 grain of moisture per hour per sq ft, per inch of mercury diff in pressure
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
Vapor barrier placement
in very cold climates, place vapor-imperable barrier on warm side of insulation, inside, with a vapor-permeable air barrier on the cold side, outside, in case of weather moisture coming in
in very hot climates, vapor-impermeable placed on warm side of insulation, outside, also acts as air barrier
in mixed climates, a vapor-permeable air barrier should be placed on the outside of the insulation, vapor passes freely
Climate zones & vapor barriers
1A, 2A, 3A = hottest, humid
2B = hot, dry
3A, 4A = mixed, humid
3B, 4B = mixed, dry
4C = cool, marine
5A, 6A = cool, humid
5B, 6B = cold, humid
7, 8 = very cold, sub-arctic
1,2,3,4: no Class I/IIvvapor barriers on inside of framed walls
marine 4, 5,6,7,8: Class I/II vapor barriers req on inside of framed walls
Class III only allow where wall assembly reqmts met
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
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
