According to California Title 24, what is the minimum aged solar reflectance requirement for cool roof products on steep-slope residential roofs in Climate Zone 2?
Correct Answer
C) 0.20 (20%)
Title 24, Part 6, Section 150.1(c)5 requires steep-slope cool roof products to have a minimum aged solar reflectance of 0.20 (20%) in most California climate zones including Zone 2. This energy efficiency requirement helps reduce cooling loads and urban heat island effects.
Why This Is the Correct Answer
Title 24 Part 6, Section 150.1(c)5 requires a minimum aged solar reflectance of 0.20 (20%) for steep-slope cool roof products in Climate Zone 2. 'Aged' reflectance accounts for weathering and soiling over time, making it a more realistic performance standard than initial/new reflectance.
Why the Other Options Are Wrong
Option A: 0.15 (15%)
0.15 (15%) is below the minimum required threshold of 0.20. A product with only 15% solar reflectance would not qualify as a code-compliant cool roof in Climate Zone 2 and could result in higher cooling loads and a failed Title 24 compliance check.
Option B: 0.30 (30%)
0.30 (30%) exceeds the minimum requirement and while desirable for performance, is not the mandatory minimum set by Title 24 for Climate Zone 2. Confusing a higher performance target with the code minimum is a common error.
Option D: 0.25 (25%)
0.25 (25%) is higher than the required minimum of 0.20. It may sound like a reasonable threshold but does not match the specific Title 24 Part 6 requirement for steep-slope residential roofs in Climate Zone 2.
Memory Technique
Remember '20% for Zone 2': both numbers contain a 2. Climate Zone 2 → 0.20 aged solar reflectance. You can also associate it with the phrase 'twenty percent in zone two' — the matching digit makes it easy to recall during the exam.
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