Building Envelope Flashcards

What is the primary purpose of a vapor retarder in a wall assembly?

Answer: To limit moisture diffusion through the assembly

A vapor retarder limits moisture vapor diffusion through the building envelope, reducing condensation risk within wall cavities.

In a hot-humid climate, where should the vapor retarder typically be placed in a wall assembly?

Answer: On the exterior (warm-in-summer) side

In hot-humid climates, moisture drives inward from outside, so the vapor retarder belongs on the exterior side of the assembly.

Which blower door metric directly represents building airtightness normalized by conditioned floor area?

Answer: CFM50

CFM50 per square foot of conditioned floor area is the standard BPI metric for normalizing airtightness to floor area.

A 'thermal bridge' in a wall assembly most commonly results in which problem?

Answer: Localized cold spots that can lead to condensation and mold

Thermal bridges conduct heat faster than surrounding materials, creating cold interior surface spots where condensation and mold can develop.

What does 'stack effect' refer to in building science?

Answer: Pressure difference caused by indoor/outdoor temperature difference driving air movement

Stack effect is the buoyancy-driven pressure difference between indoor and outdoor air caused by temperature (and thus density) differences.

According to BPI standards, what is the maximum recommended CO concentration in living spaces during a combustion appliance zone (CAZ) test?

Answer: 35 ppm

BPI standards set a 35 ppm threshold for CO in living spaces as a health-based safety limit during CAZ diagnostics.

Which type of window glazing most effectively reduces solar heat gain while maintaining visible light transmittance?

Answer: Low-e coating with spectrally selective properties

Spectrally selective low-e coatings block infrared radiation (heat) while allowing visible light through, yielding a low SHGC with high VT.