What Is R-Value for Insulation? Explained & Myths Debunked



When it comes to insulation, the term “R-value” is often mentioned, but what exactly does it mean? Unfortunately, it is a bit confusing, and the answer should be more straightforward.

But, once you get some background into how it  was created and measured, you’ll easily be able to answer the question when someone asks, “what is R-value?”

First: What Is R-Value?

R-value is a measure of a material’s ability to resist heat flow. Before 1945, the U-factor measured this, with lower U-factors being better at resisting heat.

Rated vs. Real World R-Values

The rated R-value is a regulated number. The regulation requires insulation to be labeled with a rated R-value derived from one of four approved test methods. Real-world R-value is a dynamic number that changes depending on various factors. 

Discover the Different Types of R-Value

- Material R-Value - Center-of-Cavity R-Value - Clear-Wall R-Value - Whole-Wall R-Value - Overall R-Value

Why We Shouldnt Just Be Looking at R-Value

R-value is important, but air leakage is also crucial in determining insulation performance. The R-value test can measure the effects of convective loops within insulation but not the amount of air that may leak through the wall assembly once installed.

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