Module 2 Section 2 Insulation/Ventilation Study Cards Flashcards
The primary function of insulation is to__
control heat loss
A vapor retarder is designed to__
restrict vapor diffusion
What are the implications of an inadequate air/vapor barrier
moisture may get into the building structure, causing damage
Name 2 purposes of house ventilation
- flushes moisture from unconditioned spaces in winter & heat from these spaces in summer
- provides fresh air for building occupants
Relative humidity
the amount of moisture in the air relative to the amount it could hold if saturated, expressed as a percent
drying potential
ability of a material or assembly to dry out after it has gotten wet
Why are roofs vented in the winter in cold climates?
We were not able to completely to stop air leakage into cool roof spaces, so we need to get rid of that warm, moist air.
Purpose of a heat recovery ventilator:
To transfer some of the heat from the air exhausted from the house into the fresh air coming into the house
Term ventilation might mean 2 very different things with respect to homes. 2 different types of ventilation:
- venting of roof & wall spaces to flush warm moist air out of the building components
- exhausting stale air & supplying fresh air to the living spaces
Indicate where the air/vapor barrier should be located in the wall assembly in a hot, humid climate.
outer part of wall, or not at all
4 common forms that insulation materials may be found in:
- loose fill
- batts or blankets
- rigid boards
- foamed-in-place
10 common insulation materials:
- fiberglass 6. extruded polystyrene
- cellulose fiber 7. closed cell phenolic plastic
- mineral wool 8. polyisocyanurate
- vermiculite/perlite 9. polyurethane
- expanded polystyrene 10. isocyanate/polyisocyanate
What forms do insulation materials come in?
loose, fill, batt, board
loose fill
board
foamed in place
Function of an air barrier:
to stop air movement through building walls/roofs
Indicate 2 reasons we are interested in controlling air movement through building walls and roofs.
- minimize heat flow to exterior/interior
- minimize moisture flow to building components
Describe the function of a vapor barrier
protect building from moisture damage. designed to protect from moisture due to vapor diffusion, not air movement
2 other names for vapor barriers:
vapor retarder, vapor diffusion retarder
Is it more important for the air barrier or vapor barrier to be continuous?
air barrier
Should the vapor barrier be on the warm side or cold side of the wall assembly?
warm side
Should the vapor barrier be on the warm side or cold side of the wall assembly in a hot, humid climate?
warm side
3 functions of roof vents:
- allow warm, moist air out of attic
- reduce attic temps in summer
- helps prevent ice dams in winter by keeping attic cold
4 types of roof vents:
- soffit
- ridge
- roof
- gable
Percentage of total venting should be at soffits?
50%
Percentage of total venting should be high on roof?
50%
When can soffit venting be omitted safely?
If there are gable vents at opposing ends
What do soffit vents baffles do?
prevent insulation from covering the vents
How are mansard or gambrel roofs ideally vented?
- required a ridge & bottom of upper section
- none is required for steep section
Is it possible to over-ventilate an attic? If so, why is this an issue?
- Yes, if ceiling is not well sealed
- can cause negative pressure in attic that promotes warm, moist air to enter at a faster rate
What should you wear when inspecting attics? (3 things)
- mask
- goggles
- long sleeves with tight cuffs
List 3 things that may make attics dangerous:
- fall through ceiling
- electric shock
- irritate lungs
4 common access hatch problems & the implications of each:
- not insulated: results in heat loss
- not weather stripped: results in heat loss & air leakage
- missing: results in heat loss & air leakage
- inaccessible: limits inspection
What are the implications of insulation that is only 2 inches thick, wet, compressed, interrupted by gaps or voids, or missing?
- 2” thick: heat loss
- wet: won’t work well/damage to finishes
- gaps/folds: localized heat loss, ice damming
- compressed: reduced R-value
- missing: heat loss, ice damming
Under what circumstances should insulation cover recessed lights? What is one inspection strategy to help identify recessed lights while in the attic?
only if lights are proper type, or installed in drywall boxes; look for double shell, or IC stamp
Will you ever see walls in attics? Where? Should they be insulated?
Walls indicate skylights or light wells;
yes, should be insulated
What 2 things should you be looking for on ducts in attics?
- insulation
- air/vapor barrier
How should insulation be handled around masonry chimneys?
Masonry chimneys should only have noncombustible insulation surrounding them.
How should insulation be handled around metal vents?
Vent is contained in a boxed-in area to keep insulation away
What are the implications of air/vapor barriers that are missing or incomplete?
- air leakage
- rot damage
- insulation gets wet from condensation
3 common problems with roof vents & implications:
Problem: birds nests-implication: inadequate venting
Problem: mechanical damage-implication: mold/rot
What is suggested by snow on attic insulation below roof vents?
If soffit venting is missing, rain & snow may actually be drawn into the roof vents
3 possible concerns with turbine vents:
No ventilation on calm days; too much ventilation; too much ventilation on windy days; noisy or seized
Should power vents be operating in the winter? Why or why not?
No, they can depressurize the attic, increasing heat loss
What is suggested by mold or rot on rafters & sheathing?
an exhaust fan dumping warm, moist air directly into the attic
Describe is one sentence, 4 general approaches to insulating flat & cathedral roofs
Treat as an attic-w/a little insulation & an air space
Completely fill roof space-in theory it stops air flow
Insulate above sheathing-roof membrane applied over insulation
Insulate below roof structure-lowers ceiling heights, but provides good ventilation
5 common problems found with flat rood insulation systems.
- too little insulation
- wet, compressed or voids
- missing or incomplete air/vapor barrier
- missing or inadequate venting
- venting obstructed
Implications of problems with flat roof insulation systems:
- heat loss, no damage to structure
- reduced R-values, mold/mildew/rot
- mold/mildew/rot
- warm, moist air condensing & cause mold/mildew/rot
- mold/mildew/rot
One possible way to get a look at insulation in a flat roof.
- remove ceiling light fixture or exhaust fan covers;
- pop fascia vents off & look through holes
What things might suggest wet insulation:
staining; sponginess or dampness on ceilings
Describe 2 strategies used to deal w/venting of flat roofs:
- vent roof space
- seal roof cavity
On a flat roof, where will you most often see vents?
opposing fascias
Appropriate ratio of vent area to roof area:
One square foot of venting for every 150 sqft of roof area
Basement wall insulation is necessary. T/F
False
In 2 sentences each, 2 strategies for insulating basement walls.
Outside-keeps walls warm, no interior space lost, no interior living space lost, etc, but but only certain types of insulation are suitable
Inside-inexpensive, can be done at anytime, any type of insulation is suitable, can be difficult to detect leaks.
Describe in one sentence each, 2 general approaches to insulating crawl spaces.
- insulate walls, creating a conditioned crawlspace
- insulate floor above, creating an unconditioned crawl space
All crawl spaces should be vented. T/F Explain
True if unheated-vent to outdoors to remove warm, moist air in cold climates.
List 3 safety issues involved in inspecting crawlspaces.
- wet floors
- animals
- dark & dirty
List 9 common problems w/insulation & ventilation in basement & crawlspace areas.
- insulation-too little/incomplete
- exterior insulation not suitable for below grade use
- exterior insulation not protected at top
- insulation missing at rim joists
- insulation sagging, loose or voids
- exposed combustible insulation
- air/vapor barrier missing, incomplete or wrong location
8.no moisture barrier on basement walls - no moisture barrier on earth floor
List the implications of crawlspace problems:
- higher heating/cooling costs
- lower R-value due to moisture
- mechanical damage from lawn mowers, lawn equipment
- increased heating cost
- risk of fire
- wet insulation, reducing R-value
2 possible strategies for keeping floors over unheated spaces warm:
- heated cavity between floor & insulation below
- spray-in-place foams that fill entire cavity
List 7 areas where floors over unheated spaces may feel cool:
- above garage
- above porch
- cantilevered areas
- over breezeway
- over unheated crawl space
- over open areas
- below windows projecting out from building
