Cormar Primo Grande (1.4 TOG) with Cloud 9 Charleston 9 (2.5 TOG) gives a combined 2.9 in-situ TOG. Whether that passes the 2.5 TOG underfloor heating limit and what to do.
Updated 05 September 2026.
Cormar Primo Grande and Cloud 9 Charleston 9: combined TOG for underfloor heating
The combined TOG for Cormar Primo Grande over Cloud 9 Charleston 9, worked against the UHMA underfloor heating rule.
Combined against the UHMA 2.5 TOG underfloor-heating limit. Under 1.5 also suits a low-temperature heat pump.
| Carpet | Cormar Primo Grande (1.4 TOG) |
|---|---|
| Underlay | Cloud 9 Charleston 9 (2.5 TOG) |
| Published sum | 3.9 TOG |
| UHMA in-situ correction | minus 1 TOG |
| Combined in-situ TOG | 2.9 TOG |
| Standard UFH limit | 2.5 TOG |
| Heat pump target | under 1.5 TOG |
Cormar Primo Grande is rated 1.4 TOG and Cloud 9 Charleston 9 is rated 2.5 TOG. Laid together the combination is what the underfloor heating has to warm through.
The published TOG figures add to 3.9, and even after the UHMA 1 TOG in-situ correction the pair sits at 2.9 TOG, 0.4 TOG over the limit. The carpet is fine; the underlay is doing the damage. Keep Cormar Primo Grande and drop to a low-TOG underlay such as Duralay Heatflow for Carpet (0.75 TOG) or Duralay Technics 5 (0.56 TOG), which brings the combined figure back into range.
Questions and answers
Cormar Primo Grande and Cloud 9 Charleston 9: combined TOG for underfloor heating?
Combined in-situ TOG is 2.9, above the 2.5 TOG limit, so Cormar Primo Grande with Cloud 9 Charleston 9 is not suitable for underfloor heating. Keep the carpet and switch to a low-TOG underlay.