How thick a concrete wall would be needed to give the same insulating value as 3 and a half inches of fiberglass?

Answer 1

Poured concrete has an R value of about 0.08/inch. Fiberglass batt has an R value of about 3.14/inch (blown fiberglass wall insulation is about 3.2/inch). From these values we can calculate that the equivalent insulating thickness of concrete would be about 3.5x3.14/0.08 = 137.4 inches.

Note that concrete blocks have a somewhat better insulating value due to the incorporated air pockets.

A 4" concrete block has an R value of about 0.2/inch

An 8" concrete block has an R value of about 0.15/inch

A 12" concrete block has an R value of about 0.1/inch

Answer 2

To provide the same insulation value as 3.5 inches of fiberglass, a concrete wall would need to be approximately 15-18 inches thick. Concrete is a poor insulator compared to fiberglass, so a much thicker wall is needed to achieve similar insulation properties. Alternatively, adding insulation material within the concrete wall can help improve its insulating capabilities.

Answer 3

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