CSLB C-39 Roofing ContractorEstimating and PlanningEasy
A commercial building has an attic space of 2,000 square feet. According to California Building Code (CBC) Section 1203.2, if no vapor retarder is installed, the ratio of net free ventilation area (NFVA) to attic floor area must be at least 1:150. What is the minimum required total net free ventilation area for this attic?
- A15 sq ft
- B10 sq ft
- C20 sq ft
- D13.33 sq ft
Show answer & explanationAnswer & explanation
Correct answer: D. 13.33 sq ft
The requirement is 1:150 of the attic floor area. So, 2,000 sq ft / 150 = 13.33 sq ft.
Why the other options are wrong
- A. This would be for a 1:133 ratio, not 1:150.
- B. This would be for a 1:200 ratio, not 1:150.
- C. This would be for a 1:100 ratio, or if the attic was 3,000 sq ft at 1:150.
Attic Ventilation Ratio (No Vapor Retarder)
The minimum net free ventilation area required for an attic space when no vapor retarder is installed, as specified by building codes (typically 1:150 of the attic floor area).
- Code requirement is 1:150 when no vapor retarder.
- Ratio is NFVA (Net Free Ventilation Area) to attic floor area.
- Adequate ventilation prevents moisture buildup and heat issues.
Memory trick: No vapor? 150 is the magic number for fresh air!