Underfloor Heating

New research by the Carpet Foundation in conjunction with the Underfloor Heating Manufacturers Association (UHMA) has proved conclusively that any carpet can be used over an underfloor heating system without impairing the performance of the system. The work, which used a room sized test chamber as opposed to the traditional double plate test, showed that carpet and any underlay system with a combined thermal resistance of less than 2.5 tog allows the underfloor heating system to operate efficiently. New indications are that for the majority of carpet styles the thermal resistance will be less than 1 tog. The findings cast doubt upon the validity of the previous industry standard of 1.5 tog.

The jointly funded project used the extensive testing facilities of BSRIA in Bracknell. Five different carpet types (a wool rich Axminster; wool rich cut pile Tufted; synthetic cut pile Tufted; all wool loop pile Tufted; synthetic loop pile Tufted) and two different underlays (waffle sponge rubber and crumb rubber) were tested over an underfloor heating system in a 4m square by 3m high test chamber. The results showed that:

• none of the carpet/underlay combinations interfered with the efficient warming of the airspace in the room above
• The tested tog values of the carpets (using the test chamber as a life size 'tog' meter) were significantly lower than the previous laboratory test values
• The previous double plate test was of no value when it came to underfloor heating