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Mineral Wool Insulation R Value

Rockwool Insulation r Value

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R-value is a measure of thermal resistance, measuring the heat transfer through a material per unit of area. This measure is used widely in the construction trades, both residential and commercial.

The r-value of rockwool acoustic insulation and mineral wool insulation varies widely. It really depends on what form the wool is in.

Press or formed rolls and sheets will have a different thermal resistance than loose fill type insulation. Blown rockwool insulation r value is approximately R-3.1 to R-4.0.

Rockwool R Values in Practice

In general, you can increase the r-value of a given wall by increasing the thickness or density of the insulator. For a simple example, if you were to triple the thickness of fiberglass batting in a wall cavity, the r-value would also triple.

However, if you were to forcibly press two layers of insulation into the thickness of one, you will get more r-value but most likely not a double r-value because it is improperly installed.

The r-value published by manufacturers applies strictly to the insulation that is installed in a proper fashion.

Finishing off a wall with paneling or sheetrock does not provide a substantial additional r-value.

R-Value Units

R values are usually given without their units, so it can be confusing what the value of “R-4.0” refers to. In most places in the world, the R-value is given in an international system of units (SI), while in the United States it is more common to use traditional US units.

The trick to remember is US R-values are around 6 times larger in magnitude than SI R-values. If you have an understanding of that you can quickly decipher what units you are dealing with.

SI units: m²·K/W US units: ft²·°F·h/Btu.

Typical R-Values for Insulations

Here is a useful table of r values from Colorado Energy.

Tom Davidson

I'm a Design Engineer, husband, and Dad to two. I have a taste for building, playing bad golf, and tackling all kinds of home improvement projects. Read more about the SPT Team.

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