Underlay TOG rating

Cormar Primo Tweeds TOG value and underfloor heating

The published Cormar TOG value for Cormar Primo Tweeds and the underlay budget it leaves over a heated floor.

1.2TOG

Suitable for UFH

Leaves 1.3 TOG of the combined budget for the carpet on top before the 2.5 TOG limit is reached.

PassMarginalFail

Published value

Range	Cormar Primo Tweeds
Construction	polypropylene tweed loop
TOG rating	1.2 TOG
Max underlay TOG for UFH	2.3 TOG

Cormar Primo Tweeds is a polypropylene tweed loop with a published TOG value of 1.2. A flecked tweed loop rated 1.2 TOG, comfortably within range for a heated floor with a low-TOG underlay.

Using the UHMA rule, in-situ resistance is carpet plus underlay minus 1. To keep Cormar Primo Tweeds under the 2.5 TOG limit the underlay must be no more than 2.3 TOG.

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.

Underlay pairings

Cormar Primo Tweeds with Duralay Technics 5combined 0.76 TOG Cormar Primo Tweeds with Duralay Heatflow for Carpetcombined 0.95 TOG Cormar Primo Tweeds with Tredaire King (Duralay King)combined 1 TOG Cormar Primo Tweeds with Duralay Durafit 650combined 1.3 TOG Cormar Primo Tweeds with Tredaire Softwalkcombined 2.89 TOG Cormar Primo Tweeds with Tredaire Dreamwalkcombined 3.33 TOG

Sources: Cormar Carpets published carpet TOG values · UHMA guidance on underfloor heating with carpet and underlay (combined-TOG rule)