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Choosing a low-TOG underlay for underfloor heating
The underlay is the easiest lever to pull: a low-TOG type designed for heated floors lets warmth through and leaves room for the carpet under the 2.5 limit.
Thin and dense beats thick and airy
Heat resistance comes mostly from trapped air and thickness. A low-TOG underlay for underfloor heating is therefore usually a thinner, denser product, often a dense sponge or polyurethane foam engineered to conduct heat rather than hold it. It will feel firmer underfoot than a plush comfort underlay, which is the trade you make for letting the heat through.
Products built for this job often sit around 0.4 to 1.0 TOG. Some carry a stated low-TOG or underfloor-heating suitability on the datasheet, which is the quickest way to spot them.
What to steer clear of
Thick crumb-rubber and high-density comfort foams are the usual culprits behind a failed combination. Excellent underfoot in an unheated room, they can reach 1.5 TOG or more on their own and leave almost no headroom for the carpet before you hit the 2.5 limit. If the underlay is being sold on how soft and warm it feels, treat that as a warning over underfloor heating.
Match the underlay to the carpet you want
The right underlay depends on the carpet. A lower-TOG carpet around 1.0 TOG can tolerate a slightly thicker underlay and still pass. A warmer carpet nearer 1.7 TOG needs the leanest low-TOG underlay you can find to keep the pair under the limit. Decide the carpet first, then work backwards to the underlay that keeps the sum legal.
Our tool lists real low-TOG underlays with their published figures so you can see at a glance which ones leave room for your chosen carpet.
Confirm before commissioning
A low-TOG underlay gets you a suitable floor, but the installer still sets the flow temperature and commissions the system. Show them the exact underlay and carpet you plan to use so they can confirm the combination will heat the room as expected.
Find a low-TOG underlay that fits your carpet
Open the underlay TOG toolBrowse real underlays by TOG and check them against your carpet.Find low tog underlay underfloor heating on eBayaffiliateRelated
Sources: Interfloor (Duralay/Tredaire) ยท Ball & Young