Building Science Fundamentals 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 Fundamentals flashcards as text
What is the 'dew point' temperature and its significance in building science?
Answer: The temperature at which air becomes saturated and water vapor begins to condense
Dew point is the temperature at which air reaches 100% relative humidity; when a surface falls below this temperature, condensation forms on it.
Which principle explains why basements in cold climates are prone to moisture problems even without rain water intrusion?
Answer: Warm humid summer air infiltrates the basement and condenses on cool below-grade surfaces
In summer, warm humid outdoor air entering a cool basement reaches surfaces below its dew point, resulting in condensation — a classic building science moisture problem.
A HERS rater is evaluating a home with spray foam insulation in the rim joist area. What is the primary benefit of this approach compared to batt insulation alone?
Answer: Spray foam simultaneously provides both insulation and air sealing in a notoriously leaky area
Rim joists are major air leakage sites; spray foam seals gaps and insulates simultaneously, addressing both thermal and air barrier functions in one application.
What is the relationship between sensible heat and latent heat in building HVAC loads?
Answer: Sensible heat changes air temperature; latent heat involves the energy of phase change (moisture)
Sensible heat changes the dry-bulb temperature of air, while latent heat is associated with moisture (water vapor) addition or removal without temperature change.
In building science, what does the term 'vapor retarder' (formerly 'vapor barrier') classify?
Answer: A material classified by its water vapor permeance (perms) that slows vapor diffusion
Vapor retarders are classified by their perm rating: Class I (<0.1 perms), Class II (0.1–1.0 perms), and Class III (1.0–10 perms) per IECC.
Why is 'thermal mass' particularly beneficial in climates with large diurnal temperature swings?
Answer: Thermal mass absorbs heat during the day and releases it at night, dampening temperature fluctuations
Materials with high thermal mass (heat capacity) store energy during warm periods and release it when temperatures drop, reducing peak loads and shifting energy use.
Which building science concept explains why a house can have both high insulation levels and still experience significant heat loss?
Answer: Air leakage can bypass insulation, making airtightness equally important as insulation
Even high R-value insulation is ineffective if air leaks bypass it — air sealing and insulation must work together for energy-efficient performance.