Why insulate basement walls?

Basement walls can account for up to 25% of a home’s heat loss. Closed-cell foam thicker than 1.5 inches also creates a vapor barrier so the A/C and dehumidifier run less.

What R-value do rim joists need in Indiana?

Indiana is climate zone 5, so rim joists should be at least R-20. If you look up and see bare wood framing, you are losing heat.

Basement Insulation

Rim joist spray foam insulation in a Westfield, IN basement

Basements

Basement walls can account for up to 25% of a home's heat loss. This is due to the large surface area of uninsulated basement walls and the fact that earth is a poor insulator. Closed Cell spray foam sprayed at greater than 1.5" creates a vapor barrier. By spray foaming and insulating basement walls, you are preventing water vapor from entering your basement. This allows your A/C and dehumidifier to run less often, decreasing your energy costs.

Rim Joists

Rim joists can be a major source of heat loss in a home. Rim joists are the pieces of lumber that run around the perimeter of a home, above the foundation, and in contact with the subfloor and sill plate. They can be leaky and under-insulated, allowing air to enter the home through gaps in the siding.

Insulating rim joists can help reduce heat loss, air leaks, and moisture infiltration. It can also help maintain a consistent temperature and lower energy bills. The recommended R-value for rim joists depends on the climate zone:

Climate zones 1–4: Minimum R-value of R13
Climate zones 5–8: Minimum R-value of R20

To check if your rim joists are insulated, you can look up into your basement or crawl space. If you see the wood framing without insulation, that means you're losing heat.

When selecting an insulation product, it's important to consider how it will interact with moisture in the assembly. Proper assembly design and construction is also key to long-term durability.

Longer guides: rim joist insulation in Indiana basements and crawlspace vs basement in Hamilton County.

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Common questions

Why insulate basement walls?: Basement walls can account for up to 25% of a home’s heat loss. Closed-cell foam thicker than 1.5 inches also creates a vapor barrier so the A/C and dehumidifier run less.
What R-value do rim joists need in Indiana?: Indiana is climate zone 5, so rim joists should be at least R-20. If you look up and see bare wood framing, you are losing heat.