Underlay TOG rating

Cloud 9 Cumulus TOG rating and underfloor heating

The published TOG and datasheet figures for Cloud 9 Cumulus, and what it means over a heated floor.

3.1TOG

Too warm for UFH

Already 0.6 TOG over the 2.5 TOG limit on its own, before any carpet is added.

PassMarginalFail

Cloud 9 Cumulus is rated 3.1 TOG. That alone is above the 2.5 TOG combined limit for underfloor heating, so it is not suitable over a heated floor with any carpet.

Published datasheet

Manufacturer	Ball & Young
TOG rating	3.1 TOG
Thickness	11 mm
Density	PU foam
Sound	43 dB impact reduction
Underfloor heating	Not suitable

Cumulus is Ball & Young's 11 mm luxury PU foam underlay. At 3.1 TOG it is built to insulate a cold floor, which is exactly the opposite of what an underfloor heating system needs above it.

Because Cloud 9 Cumulus is already 3.1 TOG before any carpet is added, no carpet brings the pair back under the 2.5 TOG limit. Over underfloor heating, swap it for a low-TOG underlay instead.

TOG measures thermal resistance, so a low number means heat passes through easily. For a floor covering over underfloor heating that is what you want. A comfort underlay chosen for warmth underfoot does the opposite job and is the usual reason a heated floor underperforms after a carpet goes down.

Pairings and alternatives

Cormar Pimlico with Cloud 9 Cumuluscombined 3.1 TOG Cormar Primo Textures Ribbed with Cloud 9 Cumuluscombined 3.1 TOG Cormar Primo Textures Weave with Cloud 9 Cumuluscombined 3 TOG Cormar Apollo Plus with Cloud 9 Cumuluscombined 3.2 TOG Cormar Apollo Elite with Cloud 9 Cumuluscombined 3.6 TOG Cormar Fairisle with Cloud 9 Cumuluscombined 3.6 TOG

Sources: Ball & Young Cloud 9 Cumulus underlay specification · UHMA guidance on underfloor heating with carpet and underlay (combined-TOG rule)