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Insulation Terms to Know: K-Value, R-Value, U-Value

While we make it a point not too use too much industry jargon while talking with our customers, it is inevitable that a few technical terms — like K-value, R-value and U-value — will come up. If we've used any of these in our meetings before and neglected to explain (sorry about that!), here's what we meant.

K-value, R-value and U-value all have something to do with how effective an insulating material will be. More specifically, we're looking at a product's ability to reduce heat exchange between a surface and the environment — the whole point of insulation!


K-value is shorthand for "thermal conductivity," a.k.a. how quickly heat flows through one square foot of insulating material. If two items of the same temperature are made to touch, no heat will flow from one item to the other. However, if there is a temperature difference, or "gradient" as we call it, heat will start to flow.

If there's insulation in between, heat transfer between the two objects will happen more slowly. This is why you would look for insulation with a low K-value, as this will help keep conditioned air inside your building. Make sense?


R-value, or "resistance value," is a standard rating system that describes how certain building insulation products perform when compared to their peers. For the most part, R-value increases in tandem with an increase in product thickness. So a 2-inch thick material will have twice the R-value of a 1-inch thick material.

When you do your research, look for a material with a high R-value. This signifies that the material can resist heat transfer well.


U-value, rather than identifying the thermal performance of a single material, identifies the thermal performance of a system. For example, a typical home insulation system might include a combination of gypsum wall board, fiberglass batts, polystyrene insulation boards and a plastic film vapor barrier. U-value takes all of these components into consideration. And if this sounds hard to calculate, it is!

The lower the U-value, the lower the rate of heat transfer. A well-insulated building will have a much lower U-value (and much less heat transfer) than an uninsulated or poorly insulated building.

You learn something new every day, right?

If you want a much closer look at the standardized terminology we use to determine these definitions, you can read this. It's not exactly thrilling stuff, but if you were the kind of kid who used to read the dictionary for fun, you might enjoy it!

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