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Will my carpet work over underfloor heating

A carpet suits underfloor heating when its TOG, added to the underlay beneath it, stays at or below the 2.5 combined limit.

It is the pair that passes, not the carpet alone

There is no simple yes or no for a carpet on its own, because the underlay changes the outcome. A carpet that fails over a thick comfort underlay may pass over a lean low-TOG one. So the honest answer to whether your carpet will work is: it depends on what you put under it, and on the two figures adding to 2.5 TOG or less.

Start by finding the carpet TOG from the manufacturer. Many Cormar ranges, for example, publish it. If yours does not list one, ask the retailer before assuming.

Rough carpet TOG bands

Many standard carpets fall somewhere around 1.0 to 1.7 TOG. A carpet nearer the low end leaves more room for the underlay. A carpet nearer the high end demands the leanest low-TOG underlay to stay under the limit. Thick, deep-pile and heavily backed carpets tend to sit higher, which is why the warmest-feeling carpets are the hardest to make work over underfloor heating.

Use the exact figure for your product rather than the band; the band is only a sense of where to expect it to land.

Run the sum against 2.5

Once you have the carpet TOG, add the underlay TOG and compare the total to 2.5. If you are at or below, the carpet works with that underlay. If you are over, you keep the carpet and switch to a lower-TOG underlay, or accept the carpet is not suited to underfloor heating.

Our tool holds published TOG figures for real carpets and underlays, so you can test your carpet against several underlays in seconds.

When to change the carpet instead

If even the leanest underlay cannot bring a very warm carpet under the limit, the carpet itself is the problem, and a lower-TOG covering is the fix. That is uncommon with a sensible low-TOG underlay, but it does happen with the thickest, plushest carpets.

Related

Sources: Cormar datasheets · Underfloor Heating Manufacturers Association (UHMA)