InterNACHI Insulation and Ventilation 5 — Questions and Answers
Question 1: Under ASHRAE 62.2, what is the minimum recommended whole-building mechanical ventilation rate for a 2,000 square foot home with 3 bedrooms?
- 25 CFM
- 45 CFM (Correct answer)
- 60 CFM
- 75 CFM
Correct answer: 45 CFM
ASHRAE 62.2 uses a formula based on floor area and number of bedrooms; for a typical 3-bedroom, 2,000 sq ft home the result is approximately 45 CFM of continuous ventilation.
Question 2: What deficiency does an inspector report when vermiculite insulation is found in an attic of a home built before 1990?
- Vermiculite has a very low R-value and should be replaced with modern insulation
- Vermiculite from that era is likely to contain asbestos and is a potential health hazard (Correct answer)
- Vermiculite absorbs moisture and should be removed to prevent structural damage
- Vermiculite is combustible and creates a fire risk in contact with recessed lights
Correct answer: Vermiculite from that era is likely to contain asbestos and is a potential health hazard
Most vermiculite sold before 1990 came from the Libby, Montana mine and was contaminated with asbestos; its presence should trigger an asbestos testing recommendation.
Question 3: What is the purpose of an 'energy recovery ventilator' (ERV) compared to a standard heat recovery ventilator (HRV)?
- ERVs recover both heat and moisture from exhaust air; HRVs recover heat only (Correct answer)
- ERVs use electric resistance heating to temper incoming air; HRVs use heat exchange only
- ERVs are designed for cooling climates only; HRVs are for heating climates only
- ERVs exhaust more air than they supply; HRVs maintain balanced airflow
Correct answer: ERVs recover both heat and moisture from exhaust air; HRVs recover heat only
An ERV transfers both sensible heat and moisture (latent energy) between incoming and outgoing air streams, while an HRV transfers only sensible heat.
Question 4: A home inspector finds kraft-faced fiberglass batts installed with the facing toward the exterior (cold side) in a Climate Zone 6 wall. What is the concern?
- The facing will prevent the wall from drying toward the interior
- Facing toward the cold side places the vapor retarder on the wrong side, trapping moisture in the cavity (Correct answer)
- Kraft facing is not rated for use in climate zones above Zone 4
- The facing will reduce the R-value by compressing the fiberglass fibers
Correct answer: Facing toward the cold side places the vapor retarder on the wrong side, trapping moisture in the cavity
In cold climates, the vapor retarder should be on the warm (interior) side; placing it on the cold side traps moisture driven from the interior inside the wall cavity.
Question 5: What condition is indicated when an inspector observes dark staining on attic insulation directly below roof sheathing nail tips?
- Insulation has been contaminated by animal waste
- Condensation is forming on cold nail tips and dripping onto insulation — a sign of inadequate attic ventilation (Correct answer)
- Roof shingles are bleeding asphalt through the deck onto the insulation
- Electrical arcing from improperly installed sheathing nails is scorching the insulation
Correct answer: Condensation is forming on cold nail tips and dripping onto insulation — a sign of inadequate attic ventilation
In cold weather, nail tips protruding through sheathing become cold spots where moisture condenses; the drips stain insulation below and indicate inadequate attic ventilation or air sealing.
Question 6: Which insulation installation defect is described as gaps between batt edges and framing members that reduce effective R-value significantly even when small?
- Thermal bypass
- Compression
- Voids and gaps (Correct answer)
- Wind washing
Correct answer: Voids and gaps
Voids and gaps — spaces where insulation does not make full contact with framing — allow air movement and convective loops that dramatically reduce the assembly's effective R-value.
Question 7: What is the InterNACHI-recommended action when a home inspector identifies that a crawl space has no vapor barrier over bare earth?
- Report it as a deficiency and recommend installation of a ground vapor barrier (Correct answer)
- Test the soil moisture level before deciding whether to report it
- Recommend the crawl space be converted to a conditioned space immediately
- Note it only if there is visible standing water or mold growth present
Correct answer: Report it as a deficiency and recommend installation of a ground vapor barrier
Exposed bare earth in a crawl space is a reportable deficiency; InterNACHI standards require inspectors to recommend a ground cover vapor barrier to control soil moisture evaporation.
InterNACHI Insulation and Ventilation 5
Under ASHRAE 62.2, what is the minimum recommended whole-building mechanical ventilation rate for a 2,000 square foot home with 3 bedrooms?