These 5 questions cover attic insulation, vapor retarders, attic ventilation and exhaust fans. On the National Home Inspector Examination they fall under Property Inspection (70% of the exam). Try each one before you open the answer: the explanation matters more than the letter.
1. Two attics have the same depth of insulation, but one is fiberglass batts and the other is closed-cell spray foam. The foam attic resists heat flow better because it has a higher
- vapor permeability rating
- R-value per inch of thickness
- rate of air leakage through it
- installed density rating
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Answer: B. R-value per inch of thickness
R-value measures resistance to heat flow; higher values insulate better. Materials differ in R-value per inch, so equal thickness does not mean equal performance. Inspectors estimate R-value from type and depth rather than measuring it.
Memory tip: R per inch, not just inches.
2. The inspector observes loose, pink fibrous material blown across the attic floor to a depth of about 10 inches. The inspector should describe this as
- blown-in cellulose insulation
- mineral wool batts
- spray polyurethane foam
- loose-fill fiberglass insulation
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Answer: D. loose-fill fiberglass insulation
Loose-fill fiberglass is pink, white, or yellow and fluffy; cellulose is gray and paper-like; mineral wool is dense and brown or green. Identifying the type and approximate depth lets the inspector estimate the R-value.
Memory tip: Pink and fluffy = fiberglass.
3. A crawl space with a dirt floor has no ground cover, and the joists above show condensation and mold. The MOST appropriate recommendation is
- install a polyethylene vapor retarder over the soil
- add more foundation vents around the perimeter
- remove the insulation from between the joists
- run a circulating fan in the crawl space
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Answer: A. install a polyethylene vapor retarder over the soil
A ground vapor retarder slows the evaporation of soil moisture into the crawl space. Without it, humidity rises and condenses on cool framing, feeding mold and decay. A polyethylene ground cover is the standard correction.
Memory tip: Cover the dirt.
4. An attic has a continuous ridge vent but the soffit vents are completely blocked by insulation. The MOST significant implication is
- the ridge vent will begin to admit rain
- the attic space will become over-ventilated
- the insulation will lose much of its R-value
- no intake, so the ridge vent cannot exhaust air
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Answer: D. no intake, so the ridge vent cannot exhaust air
Attic ventilation needs intake at the soffits and exhaust at the ridge or roof. Blocked intake means the ridge vent cannot pull air through, so heat and moisture stagnate. Baffles keep insulation clear of the soffit vents.
Memory tip: Exhaust needs intake.
5. What problem can occur if attic insulation blocks soffit vents?
- Reduced efficiency of the heating system
- Extra structural load on the ceiling joists
- No intake air, crippling the attic ventilation
- A fire risk from the piled insulation
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Answer: C. No intake air, crippling the attic ventilation
When attic insulation blocks soffit vents, intake air cannot enter the attic. This defeats the ventilation system, allowing heat and moisture to accumulate which can cause structural damage and ice dams.
Memory tip: Insulation blocking soffits = no intake air = failed ventilation. Use baffles to maintain clearance.