CSLB General Building (B)Finishes and Building EnvelopeMedium
Under California's Title 24 Part 6 prescriptive requirements, a new low-slope (flat) roof in most climate zones must meet a minimum aged solar reflectance to qualify as a 'cool roof.' What is that minimum aged solar reflectance value?
- A0.63
- B0.85
- C0.20
- D0.40
Show answer & explanationAnswer & explanation
Correct answer: A. 0.63
Title 24 prescriptive cool roof requirements for low-slope roofs typically require a minimum aged solar reflectance of 0.63 (with an initial reflectance around 0.70) to reduce heat absorption and cooling loads.
Why the other options are wrong
- B. Exceeds typical requirements; not the standard threshold.
- C. This value applies to steep-slope roofs, not low-slope.
- D. Below the prescriptive threshold for low-slope cool roofs.
Title 24 Cool Roof
California energy code requirement mandating minimum solar reflectance and thermal emittance for roofing to reduce building cooling loads.
- Low-slope aged reflectance minimum: 0.63
- Steep-slope aged reflectance minimum: 0.20
- Reduces urban heat island effect and cooling costs
Memory trick: 'Sixty-three keeps low-slope roofs cool and free.'