BPI Insulation Standards 2 — Questions and Answers
Question 1: What does the term 'thermal bridging' refer to in the context of insulation?
- Heat loss through conduction across a material with higher conductivity than surrounding insulation (Correct answer)
- Air movement through gaps in insulation
- Moisture condensation on cold surfaces
- Radiation of heat through insulation materials
Correct answer: Heat loss through conduction across a material with higher conductivity than surrounding insulation
Thermal bridging occurs when a conductive material (like a stud) bypasses insulation, creating a path for heat to transfer more readily.
Question 2: Which insulation material has the highest R-value per inch?
- Fiberglass batt
- Closed-cell spray polyurethane foam (Correct answer)
- Cellulose
- Mineral wool
Correct answer: Closed-cell spray polyurethane foam
Closed-cell SPF provides approximately R-6 to R-7 per inch, the highest of common insulation materials.
Question 3: According to BPI standards, what is the minimum required total R-value for attic insulation in Climate Zone 5?
- R-38
- R-49 (Correct answer)
- R-60
- R-30
Correct answer: R-49
BPI and IECC guidelines recommend R-49 as the minimum attic insulation level for Climate Zone 5.
Question 4: What is the primary purpose of a vapor retarder when installed with insulation?
- To increase R-value of the assembly
- To limit moisture diffusion into the building assembly (Correct answer)
- To provide an air barrier
- To reflect radiant heat
Correct answer: To limit moisture diffusion into the building assembly
A vapor retarder controls the diffusion of water vapor through building assemblies to prevent moisture accumulation and related damage.
Question 5: In BPI's building science framework, which metric describes the rate of heat flow through a building assembly?
- R-value
- U-factor (Correct answer)
- SHGC
- Perm rating
Correct answer: U-factor
U-factor (or U-value) measures the rate of heat transfer through an assembly; it is the inverse of R-value.
Question 6: When auditing a rim joist area, which insulation approach is typically recommended by BPI for existing homes?
- Fiberglass batt only
- Closed-cell SPF or rigid foam with air sealing (Correct answer)
- Blown-in cellulose
- Mineral wool batt without air sealing
Correct answer: Closed-cell SPF or rigid foam with air sealing
BPI recommends using closed-cell SPF or rigid foam at rim joists because these materials simultaneously insulate and air seal this leaky zone.
Question 7: What is 'settled R-value' as it applies to blown-in insulation?
- The R-value at time of installation before any compression
- The R-value after the insulation has compacted over time (Correct answer)
- The R-value measured at freezing temperatures
- The R-value per square foot of coverage
Correct answer: The R-value after the insulation has compacted over time
Settled R-value reflects the insulation's thermal resistance after it naturally compacts from its initially installed depth, which is lower than the installed R-value.
BPI Insulation Standards 2
What does the term 'thermal bridging' refer to in the context of insulation?