The Myth of R-Value and Spa Covers

R-value is a measure of the resistance of various materials to heat transfer. It is commonly used to determine the heat retention of various components of a spa cover.

Most industries that use R-value are regulated by FTC standards. When used properly, insulation can pass independent tests created by ASTM.


The Myth: Since there is no independent test for spa covers, any R-value that a dealer provides is simply an interpretation of the insulative value. This is not ideal, as it can be easily manipulated or exaggerated.

The R-value of our standard foam covers is calculated by adding the foam insulation to the spa cover thickness. This calculation shows that the foam insulation provides a higher amount of heat retention than the standard foam.

Foam Density and Foam Thickness.

These two factors affect the R-value of a particular spa cover.

It's easy to understand why a thicker and denser foam will reduce heat transfer.

This type of foam is made from varying amounts of fat and gas, and its properties can vary widely. The level of gas used in the mix can also affect the strength and density of the foam.

Our spa covers are made from rigid cellular foam, which can resist both heat and chemical damage. This material is the most expensive spa cover foam we've found.

ASTM C578 Type IV, 25 psi, 1.55 pcf density

When shopping for a spa cover, be sure to check the foam density and thickness numbers to see if they are real. Also, be aware that the new EPS we use may not be as accurate as the old ones.

Myth Busted!

R-value testing is done at room temperature, but it doesn't take into account vapor and moisture. In the spa environment, the hot water and humidity can dramatically reduce the R-value.

The R-value of a material will also decrease dramatically if it is subjected to high temperatures. For instance, if a material is tested at 75 degrees, the R-value will still decrease dramatically.

Instead of measuring the R-value of the quality of the product, look for a spa cover that has high density and weight, which can be vacuum wrapped in continuous sheets in 6 mil heat welded polyethylene.


If you have any other questions about pool and spa products please do let us know - we are here to help!

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