Building Science Principles Flashcards

Which phenomenon causes warm, moist air to condense on a cold surface inside a wall assembly?

Answer: Dew point condensation

When air cools to its dew point temperature at a cold surface, water vapor condenses into liquid moisture.

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

Answer: On the exterior side, toward the hot exterior

In hot-humid climates, the dominant moisture drive is inward from the hot exterior, so the vapor retarder belongs on the exterior side.

What does the term 'thermal mass' refer to in building science?

Answer: A material's ability to store and slowly release heat

Thermal mass describes a material's capacity to absorb, store, and release heat energy, moderating interior temperature swings.

Which heat transfer mechanism does low-emissivity (low-e) window coating primarily reduce?

Answer: Radiation across the air gap

Low-e coatings reflect infrared radiation, reducing the radiative heat transfer between the glass panes.

A HERS rater measures attic ventilation to ensure balance between intake and exhaust. What is the recommended ratio of net free area to attic floor area when using balanced ventilation?

Answer: 1:150

The standard building code ratio for balanced attic ventilation (50% intake, 50% exhaust) is 1:150 net free area to floor area.

What is the primary purpose of an air barrier in a building enclosure?

Answer: To resist convective air movement through the building shell

An air barrier controls convective airflow (infiltration and exfiltration) through the building envelope, not diffusion.

Which condition best describes a 'negative pressure' house?

Answer: Interior air pressure is lower than exterior pressure

A negative pressure building has interior pressure below outdoor pressure, causing outdoor air to be drawn inward through any gaps.