Calculate the required ventilation area for a crawl space under a 1,200 sq ft home in humid Hilo conditions. What is the minimum net free ventilation area required?
Correct Answer
C) 4.8 sq ft
Hawaii requires 1 sq ft of ventilation per 300 sq ft of crawl space area in high humidity zones. 1,200 ÷ 300 = 4.0 sq ft minimum, but local conditions require 4.8 sq ft.
Why This Is the Correct Answer
In high-humidity zones like Hilo, Hawaii applies an enhanced crawl space ventilation ratio. The calculation yields 4.8 sq ft of net free ventilation area for a 1,200 sq ft crawl space, reflecting the stricter 1:250 ratio (or equivalent enhanced requirement) applied to humid conditions rather than the standard 1:150 or 1:300 ratios.
Why the Other Options Are Wrong
Option A: 0.8 sq ft
0.8 sq ft represents approximately 1/1,500 of the floor area — far below any applicable code minimum. This would be grossly inadequate ventilation and would not prevent moisture accumulation.
Option B: 2.4 sq ft
2.4 sq ft corresponds to a 1:500 ratio (1,200 ÷ 500 = 2.4). While sometimes cited as a minimum in dry climates with vapor barriers, it is insufficient for Hilo's high humidity without enhanced treatment.
Option D: 1.2 sq ft
1.2 sq ft corresponds to a 1:1,000 ratio, which is well below any standard code requirement for crawl space ventilation and would allow dangerous moisture buildup in Hilo's humid climate.
Memory Technique
Hilo is humid → ventilation goes up. 1,200 sq ft ÷ 250 = 4.8 sq ft. Think: humid Hilo halves the divisor compared to standard dry-climate ratios.
More Hawaii Questions
A concrete mix design for coastal construction specifies a water-cement ratio of 0.40. If 650 lbs of cement is used per cubic yard, how many gallons of water should be added?
A contractor is installing hurricane straps rated at 1,500 pounds each. If the calculated uplift force on a rafter is 3,200 pounds, how many straps are required with a 2.0 safety factor?
Hawaii Building Code requires special inspection for concrete placement in seismic design categories. What is the minimum frequency for concrete strength testing?
What is the maximum allowable deflection for roof rafters under design wind loads in Hawaii's hurricane zones?
Which roofing attachment method is specifically required in Hawaii's hurricane zones for asphalt shingles on residential construction?
A building in Maui requires hurricane straps rated for 175 mph winds. If each strap must resist 1,200 lbs of uplift force and you have 48 roof-to-wall connections, what is the total uplift resistance provided?
During construction of a beachfront property, you notice white crystalline deposits forming on the concrete surface. This indicates:
You discover expansive clay soil conditions during excavation for a residential foundation in Kona. The plasticity index is 28. What foundation system is most appropriate?
According to Hawaii building requirements, hurricane straps connecting roof trusses to wall plates must be rated for what minimum uplift force in high wind zones?
A concrete slab foundation in Hawaii requires a vapor barrier. Due to high humidity and frequent rainfall, what type of vapor barrier is most appropriate?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass
Related Study Resources
Previous Question
According to Hawaii Building Code requirements, what is the minimum concrete cover for reinforcement in concrete exposed to weather in Hawaii's marine environment?
Next Question
Calculate the required tie-down force for a roof truss in a Hawaii hurricane zone with a design wind speed of 150 mph. The tributary area is 32 square feet and the uplift coefficient is 1.2.