Building Envelope & Insulation Flashcards
7 cards from real HERS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Building Envelope & Insulation flashcards as text
What is the purpose of a wind-washing barrier behind insulation in an attic knee wall?
Answer: To prevent wind from reducing insulation effectiveness
Wind washing occurs when air movement through insulation reduces its thermal resistance; a rigid barrier on the cold side prevents this.
Which climate zone(s) typically require a continuous air barrier but NOT a vapor retarder on the interior?
Answer: Climate Zones 1-2 (hot-humid)
In hot-humid climates, interior vapor retarders can trap moisture inside assemblies; an air barrier alone is the recommended moisture control strategy.
What is the minimum net free area ratio required for ventilation chutes (baffles) in a vented attic per IRC?
Answer: 1:150 of the attic floor area
IRC Section R806 requires a minimum net free ventilating area of 1:150 unless conditions allow 1:300 with balanced high/low distribution.
In HERS ratings, what is the correct term for the total area of all surfaces separating conditioned space from unconditioned space or outdoors?
Answer: Thermal envelope area
The thermal envelope encompasses all surfaces—walls, roof, floors, windows, and doors—that bound the conditioned space.
A rim joist is a common air leakage site in older homes. Which insulation method best addresses both air sealing and thermal performance at the rim joist?
Answer: Spray foam applied directly to the rim joist
Spray foam conforms to irregular surfaces, seals all gaps, and provides insulation in a single step, making it ideal for rim joists.
What does the term 'effective R-value' account for that nominal R-value does not?
Answer: Thermal bridging through framing members
Effective R-value accounts for the reduced whole-assembly thermal resistance caused by thermal bridging through studs, joists, and other framing elements.
Which of the following is classified as an air-impermeable insulation per ASTM E2178?
Answer: Closed-cell spray polyurethane foam
Closed-cell spray foam has an air permeance ≤0.02 L/(s·m²) at 75 Pa, meeting the ASTM E2178 definition of air-impermeable insulation.