Building Science Principles 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 Science Principles flashcards as text
According to building science principles, why is it important to align the air barrier, thermal barrier, and vapor control layer in a building assembly?
Answer: To prevent misalignment from creating moisture traps and thermal bypasses that degrade performance
Misaligned control layers allow air, heat, and moisture to bypass each control layer independently, creating condensation risk and energy penalties.
What is 'exfiltration' in the context of building air leakage?
Answer: Conditioned air leaking out of the building through gaps in the envelope
Exfiltration is conditioned interior air escaping outward through the building envelope, the opposite of infiltration.
In building science, what does the 'Pressure Boundary' of a house define?
Answer: The continuous plane that separates the conditioned interior from the unconditioned exterior
The pressure boundary is the continuous air barrier that encloses the conditioned volume, separating pressurized interior air from the exterior.
What is the primary risk of installing a vapor-impermeable material on BOTH sides of a wall assembly?
Answer: Any moisture that enters the assembly has no drying pathway and can accumulate
A 'moisture trap' is created when impermeable layers on both sides prevent the assembly from drying in either direction, leading to moisture accumulation.
Which climate-related factor most influences whether a HERS rater recommends a vented or unvented attic assembly?
Answer: The climate zone, humidity levels, and roof geometry
Climate zone moisture conditions and roof geometry determine whether vented attics will introduce harmful humidity or whether unvented conditioned attics are more appropriate.
What is 'wind washing' in an insulated building assembly and why is it problematic?
Answer: Air movement through or behind air-permeable insulation that reduces its effective R-value
Wind washing is air movement through permeable insulation (like batts in a vented cavity), which convectively removes heat and dramatically reduces effective thermal resistance.
How does the 'stack effect' influence air leakage patterns in a multi-story home during winter?
Answer: Warm air rises and exits near the top of the house, drawing cold exterior air in at the bottom
In winter, warm buoyant interior air rises and exfiltrates through gaps at the top of the house, while cold exterior air infiltrates through low openings.