Building Envelope and Insulation Flashcards

Degree days are used in building energy analysis to:

Answer: Quantify heating or cooling demand based on outdoor temperature deviation from a base

Heating degree days (HDD) and cooling degree days (CDD) accumulate daily temperature differences from a base (usually 65°F) to estimate seasonal heating and cooling energy needs.

Which roof assembly strategy best reduces cooling loads in a hot climate?

Answer: Cool (high-reflectance, high-emittance) roof surface

Cool roofs with high solar reflectance and thermal emittance reduce roof surface temperatures, lowering heat conduction into the building and reducing cooling energy use.

Adding continuous exterior insulation to a wall assembly primarily helps by:

Answer: Eliminating thermal bridging through framing members

Continuous exterior insulation wraps the entire wall face including studs, eliminating thermal bridges at framing and significantly improving whole-wall R-value.

Fenestration area strongly affects building energy use because windows typically have:

Answer: Much lower R-values than insulated walls, increasing heat transfer significantly

Even high-performance triple-pane windows have U-factors around 0.15-0.20 (R-5 to R-7), far lower than typical insulated walls at R-20 or higher, making windows a major heat loss/gain pathway.

Vapor retarders in wall assemblies are installed to:

Answer: Control moisture diffusion and prevent condensation within the wall cavity

Vapor retarders slow water vapor diffusion through walls, preventing moisture from condensing within the assembly and causing mold, rot, or insulation degradation.

The stack effect in tall buildings causes energy losses because:

Answer: Warm air rises and escapes at the top, drawing cold outside air in at the bottom

In winter, warm buoyant air rises and leaks out at upper floors, while cold outdoor air infiltrates at lower levels, increasing heating loads significantly in tall buildings.