BPI Air Sealing 5 — Questions and Answers
Question 1: In a balloon-framed home, what is the primary air sealing challenge compared to platform-framed construction?
- Lack of insulation in wall cavities
- Continuous stud cavities that run from basement to attic, creating vertical air bypass pathways (Correct answer)
- Excessive number of exterior wall penetrations
- Difficulty accessing attic framing members
Correct answer: Continuous stud cavities that run from basement to attic, creating vertical air bypass pathways
Balloon framing has continuous stud bays from foundation to roof with no fire stops or blocking, creating direct air bypass channels throughout the building.
Question 2: When air sealing a home with an atmospherically vented water heater, what health and safety hazard must be evaluated?
- Scalding risk from water temperature changes
- Carbon monoxide backdrafting into living space if negative pressure exceeds draft capacity (Correct answer)
- Combustion of foam sealant near the water heater jacket
- Electromagnetic interference from nearby electrical panels
Correct answer: Carbon monoxide backdrafting into living space if negative pressure exceeds draft capacity
Atmospherically vented appliances rely on positive draft; excessive negative pressure from air sealing can cause combustion gases including CO to backdraft into living areas.
Question 3: What does 'CFM25' measure in duct leakage testing?
- Cubic feet per minute of air leaking through the building envelope at 25 Pascals
- Cubic feet per minute of duct leakage at 25 Pascals of pressure (Correct answer)
- Ceiling fan airflow measured at 25 inches from the fan
- Carbon monoxide flow rate at 25 parts per million
Correct answer: Cubic feet per minute of duct leakage at 25 Pascals of pressure
CFM25 measures the volume of air leaking from the duct system when pressurized to 25 Pascals, used to assess duct system airtightness.
Question 4: Which air sealing application requires a fire-rated or intumescent product rather than standard spray foam?
- Sealing around window rough openings
- Penetrations through fire-rated assemblies such as floor/ceiling separating living floors from garages (Correct answer)
- Gaps around interior door frames
- Cracks in basement concrete walls below grade
Correct answer: Penetrations through fire-rated assemblies such as floor/ceiling separating living floors from garages
Fire-rated assemblies require intumescent or fire-rated sealants that expand when heated to maintain the assembly's fire resistance rating.
Question 5: What is the natural infiltration rate (ACH natural) approximation derived from ACH50 for an average-height building in a typical wind zone?
- ACH50 ÷ 5
- ACH50 ÷ 10 (Correct answer)
- ACH50 ÷ 20
- ACH50 ÷ 50
Correct answer: ACH50 ÷ 10
A common rule of thumb divides ACH50 by 20 for single-story buildings and by 17–20 for average conditions to estimate natural infiltration rate.
Question 6: Which of the following is a common air leakage site at the rim joist area in a basement?
- The concrete footing below grade
- Gaps between the sill plate, rim joist, and subfloor where wood meets masonry (Correct answer)
- The center of basement concrete walls
- Floor drain connections in the slab
Correct answer: Gaps between the sill plate, rim joist, and subfloor where wood meets masonry
The rim joist area where the wood framing meets the foundation wall is one of the most significant air leakage locations in homes with basements.
Question 7: When air sealing an attic hatch, which combination of measures provides both air sealing and thermal performance?
- Weatherstripping the hatch only
- Weatherstripping the hatch perimeter and adding rigid foam insulation to the hatch door (Correct answer)
- Spraying foam around the hatch frame only
- Installing a second hatch cover on top of the existing one
Correct answer: Weatherstripping the hatch perimeter and adding rigid foam insulation to the hatch door
Adding weatherstripping to seal air leakage and rigid foam to the hatch panel addresses both air infiltration and heat conduction through this critical bypass point.
BPI Air Sealing 5
In a balloon-framed home, what is the primary air sealing challenge compared to platform-framed construction?