BPI Air Sealing 3 — Questions and Answers
Question 1: Which air sealing strategy is most effective for a kneewalled attic in a Cape Cod-style house?
- Sealing only the exterior roof sheathing
- Air sealing and insulating the kneewalls, floor behind kneewalls, and attic floor between kneewall and living space (Correct answer)
- Installing spray foam on the interior of exterior walls only
- Adding insulation to the roof deck without sealing the kneewalls
Correct answer: Air sealing and insulating the kneewalls, floor behind kneewalls, and attic floor between kneewall and living space
In kneewalled attics, all three planes — kneewalls, floor behind them, and the horizontal attic floor — must be addressed to establish a continuous thermal and air boundary.
Question 2: What is 'stack effect' and why is it important for air sealing?
- The accumulation of insulation layers in a wall cavity
- Buoyancy-driven air movement where warm air rises and escapes at the top while cold air enters at the bottom (Correct answer)
- The stacking of multiple air barrier layers for redundancy
- The effect of multiple chimneys creating competing drafts
Correct answer: Buoyancy-driven air movement where warm air rises and escapes at the top while cold air enters at the bottom
Stack effect drives air infiltration and exfiltration due to temperature-induced pressure differences, making top and bottom air sealing critical.
Question 3: What is the recommended minimum CFM50 reduction goal per BPI standards when performing air sealing work?
- 5%
- 10% (Correct answer)
- 15%
- 25%
Correct answer: 10%
BPI guidelines generally target at least a 10% reduction in CFM50 as a meaningful improvement from air sealing retrofit work.
Question 4: When using a smoke pencil during a blower door test, what does the movement of smoke toward a surface indicate?
- A moisture problem behind the surface
- An air leak drawing air inward through the building envelope (Correct answer)
- Proper airflow distribution in the space
- A combustion appliance backdraft condition
Correct answer: An air leak drawing air inward through the building envelope
During depressurization testing, smoke moving toward a surface indicates an air leak where outdoor air is infiltrating.
Question 5: What is 'duct blaster' testing used to evaluate in the context of building performance?
- Whole-house air infiltration rate
- Air leakage from the duct distribution system (Correct answer)
- Combustion air supply adequacy for furnaces
- Attic ventilation airflow rates
Correct answer: Air leakage from the duct distribution system
A duct blaster pressurizes the duct system to measure leakage, which can account for 20-40% of HVAC energy losses in typical homes.
Question 6: Which location in a home typically has the greatest concentration of air leakage sites per square foot?
- Exterior wall centers
- Attic floor and ceiling penetrations (Correct answer)
- Basement slab
- Interior partition walls
Correct answer: Attic floor and ceiling penetrations
The attic floor, with its many penetrations for wires, pipes, and framing gaps, typically contains the greatest density of air leakage pathways.
Question 7: What is 'wind washing' as it relates to attic insulation and air sealing?
- Moisture damage from wind-driven rain on siding
- Airflow through or under insulation that reduces its effective R-value (Correct answer)
- UV degradation of air barrier membranes
- The cleaning of ductwork with high-velocity air
Correct answer: Airflow through or under insulation that reduces its effective R-value
Wind washing occurs when air moves through or beneath insulation, dramatically reducing its thermal performance by eliminating the still-air layer.
BPI Air Sealing 3
Which air sealing strategy is most effective for a kneewalled attic in a Cape Cod-style house?