According to California Title 24, what is the minimum solar reflectance requirement for cool roof products on low-sloped roofs in Climate Zone 2?
Correct Answer
A) 0.70
California Title 24 Energy Code Section 150.1(c)11 requires cool roof products on low-sloped roofs in Climate Zone 2 to have a minimum aged solar reflectance of 0.70 and thermal emittance of 0.75. This requirement helps reduce cooling energy consumption in California's hot climate zones.
Why This Is the Correct Answer
California Title 24, Section 150.1(c)11 mandates a minimum aged solar reflectance of 0.70 (70%) for cool roof products on low-sloped roofs in Climate Zone 2. Paired with a thermal emittance of 0.75, this standard reduces heat absorption and lowers cooling loads in California's warmer inland zones.
Why the Other Options Are Wrong
Option B: 0.55
0.55 falls well below the Title 24 requirement for low-sloped roofs in Climate Zone 2. This value might apply to steep-sloped or different climate zone scenarios, but it does not meet the 0.70 threshold mandated for this specific combination.
Option C: 0.63
0.63 is between the incorrect options and the correct answer, making it a tempting distractor. However, Title 24 does not use 0.63 as a threshold for this scenario — the standard is set at 0.70 for Climate Zone 2 low-slope applications.
Option D: 0.75
0.75 exceeds the minimum requirement, so while a roof with 0.75 solar reflectance would comply, 0.75 is not the specified minimum — it is actually the minimum thermal emittance value required alongside the 0.70 solar reflectance. Mixing up reflectance and emittance numbers is a common error.
Memory Technique
Remember '70 Reflect, 75 Emit' for low-slope in Zone 2. Visualize a 70 MPH speed limit sign painted on a reflective roof, with a 75-watt light bulb above it emitting heat — reflecting 70, emitting 75.
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