HERS Building Envelope & Insulation 2 — Questions and Answers
Question 1: Which insulation material has the highest R-value per inch?
- Open-cell spray foam
- Closed-cell spray foam (Correct answer)
- Fiberglass batt
- Cellulose
Correct answer: Closed-cell spray foam
Closed-cell spray foam provides approximately R-6 to R-7 per inch, the highest among common insulation materials.
Question 2: In RESNET standards, what is the primary purpose of a blower door test for the building envelope?
- Measure HVAC system efficiency
- Quantify air leakage through the building shell (Correct answer)
- Test duct system tightness
- Verify window U-factor compliance
Correct answer: Quantify air leakage through the building shell
A blower door test depressurizes the home to measure air leakage (ACH50 or CFM50) through the building shell.
Question 3: What does ACH50 measure in residential energy testing?
- Air changes per hour at 50 Pascals pressure difference (Correct answer)
- Average ceiling height at 50°F
- Air conditioning hours per season
- Annual cooling hours at 50% load
Correct answer: Air changes per hour at 50 Pascals pressure difference
ACH50 is the number of air changes per hour measured when the home is pressurized or depressurized to 50 Pascals.
Question 4: When insulating a cathedral ceiling without a vented air space, which approach is code-compliant?
- Standard fiberglass batts only
- Unvented assembly using air-impermeable insulation meeting IRC requirements (Correct answer)
- Vented assembly using batt insulation only
- No insulation is needed in cathedral ceilings
Correct answer: Unvented assembly using air-impermeable insulation meeting IRC requirements
Unvented cathedral ceilings require air-impermeable insulation (such as spray foam) meeting minimum R-value requirements per IRC Table R806.5.
Question 5: What is thermal bridging in a wall assembly?
- Heat transfer through a conductive element bypassing insulation (Correct answer)
- A bridge-shaped roof truss design
- Thermal mass in masonry walls
- Radiant heat distribution through floors
Correct answer: Heat transfer through a conductive element bypassing insulation
Thermal bridging occurs when a conductive material (like wood studs or steel framing) creates a path for heat to bypass the insulation layer.
Question 6: Which wall framing strategy best reduces thermal bridging compared to standard 2x4 construction?
- Single stud framing with OSB sheathing
- Advanced framing (OVE) with continuous exterior insulation (Correct answer)
- Double 2x4 plates at all corners
- Metal stud framing at 16" on center
Correct answer: Advanced framing (OVE) with continuous exterior insulation
Advanced framing combined with continuous exterior insulation minimizes framing fraction and eliminates thermal bridges through the wall assembly.
Question 7: Where should the vapor retarder be located in a cold climate wall assembly?
- On the exterior side of the sheathing
- On the warm-in-winter side of the insulation (Correct answer)
- In the middle of the insulation layer
- Vapor retarders are not needed in cold climates
Correct answer: On the warm-in-winter side of the insulation
In cold climates, the vapor retarder belongs on the interior (warm-in-winter) side to prevent moisture-laden indoor air from diffusing into and condensing within the wall cavity.
HERS Building Envelope & Insulation 2
Which insulation material has the highest R-value per inch?