Carpeting over Heated Floor

There is a type of floor becoming very popular and that is the heated floor. This type of floor is also known as the hydronic or radiant-heated floor and has been very popular in Europe for a number of years. The heat in these floors is generated in most cases by water heated between 80 degrees Fahrenheit and 125 degrees Fahrenheit. The conduit of the heated water is through flexible tubing running underneath the floor’s surface.

As you can imagine, this sounds very comfortable and warm for the feet. No longer do you have to live with the cold flooring characteristic of vinyl, wood, tile, and marble surfaces. But what if you desire carpeting? You can have radiant floor heating systems underneath carpet as well. But there is a metric you must consider when purchasing carpeting for heated floors and it is known as the thermal resistance or R-value of the carpet and its pad.

The R-value is important because of the fact that carpet is an insulator from the cold. This means that your heating system underneath has to work harder to heat from underneath to over the surface of the carpet. The water temperature will have to be higher as well. Therefore, the carpet should have a lower R-value so as to minimize the stress on the heating system. The R-value is the measure of heat resistance (insulating power). When the carpet is not so resistant to heat, it can let the heat pass through to the environment above the surface.

An R-value of 4.0 is the maximum suggested by carpet manufacturers when selecting carpet to go over heated floors. The preferred R-value is at the midpoint of 2.0. And the lower pile carpet is preferred over the high-pile carpet (less resistance to the underlying heat flow). It is even recommended that a carpet cushion be skipped but if one is used it should be no more than 3/8 inch. Even better, if you want to use a cushion, use one that is intended for a heated floor.

One efficient way to increase the heat mass is to install a suspended thermal flooring system where there is a supported slab above existing floor and tubing runs in the space between. In order to increase the heat mass efficiently, sand is used to fill the space because it is very good heat conductor. Doing this makes even carpet a good surface to place over heated floors.

Of course it still comes down to preference. Some homeowners really love carpet and would probably be able to live with the fact that their heated floor system has to work harder so that they can walk on that soft surface. A harder working heating system to maintain higher temperatures will ultimately cost you more.

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