In a cold climate, on which side of the wall insulation is a vapour retarder normally placed?
- The warm-in-winter side, toward the heated room
- Both faces of the insulation, sealing it in
- The cold-in-winter side, against the sheathing
- The middle of the cavity, between two batts
Show the answer
A. The warm-in-winter side, toward the heated room
Water vapour moves from the warm, humid interior toward the cold exterior. Placing the retarder on the warm side keeps vapour from reaching cold surfaces where it would condense. A retarder on both sides can trap moisture in the cavity.
Reference: IRC 2021 R702.7 (vapour retarders, concept)
A bathroom exhaust fan duct ends in the attic, a foot above the insulation. Why is this a defect?
- It lets attic heat flow back down into the bathroom
- It dumps moist air into the attic, where it can condense
- It makes the fan motor work against too much pressure
- It lets attic insulation fall down into the fan
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B. It dumps moist air into the attic, where it can condense
Exhaust fans must discharge outdoors. Moist air released in the attic condenses on cold framing and sheathing, leading to mold and decay. Ending the duct near a roof or soffit vent is not the same as ducting it outside.
Reference: IRC 2021 M1501.1 (exhaust discharge to outdoors)
What is the purpose of the gypsum board on the garage side of the wall between an attached garage and the house?
- To reduce the noise of the overhead door opener
- To keep vehicle exhaust from passing into the house
- To slow the spread of a garage fire into the living space
- To stiffen the wall against impact from vehicles
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C. To slow the spread of a garage fire into the living space
Garages hold vehicles and fuel, so the wall and any ceiling under living space are covered with gypsum board to give occupants time to escape a fire. Holes, missing sections and attic hatches made of thin plywood are reported as breaches of this separation.
Reference: IRC 2021 R302.6 (dwelling-garage fire separation)