Thermal, Moisture, and Openings
What is tested
Thermal, moisture, and openings tests envelope performance: insulation, air and vapor control, flashing, roofing, waterproofing, windows, doors, and glazing.
Core rules
- R-value is thermal resistance; U-factor is thermal transmittance; U = 1 ÷ total R. Add resistances in series, including surface films.
- Control layers: water, air, vapor, and thermal. The vapor retarder goes on the warm side in cold climates; in mixed climates, use a material or placement that allows drying.
- Flashings manage water at roofs, walls, windows, and penetrations. Window pan flashing, sill seal, and back dams are common exam points.
- Openings: check fire rating, egress size, safety glazing, and weather seal. Store windows upright and protect them.
- Roofing: slope, underlayment, drip edge, and counterflashing matter more than surface appearance.
Worked example
A wall has R-13 cavity insulation, R-5 continuous insulation, and R-0.68 interior plus R-0.17 exterior surface films. Total R = 13 + 5 + 0.68 + 0.17 = 18.85. U = 1 ÷ 18.85 = 0.053 Btu/(h·ft²·°F). Reasoning: thermal resistances add; U is the reciprocal of total R.
Traps
Putting a vapor retarder on both sides; treating caulk as flashing; ignoring pan flashing at windows; mixing R and U; forgetting thermal bridging of framing.