UHMA CARPET TEST RESULTS FINAL

UHMA TEST PROGRAMME REVEALS TRUE FACTS ABOUT CARPETS AND UNDERFLOOR HEATING

Underfloor heating and carpets can make perfect partners - and that's official.

A test programme carried out by The Underfloor Heating Manufacturers' Association (UHMA) has established, once and for all, that the old 1.5 Tog maximum is too low. In fact, carpets and underlays with a combined Tog rating of 2.5 can be safely used without impairing heating efficiency.

Now analysed and collated, the test results will provide UHMA Members with vital design data.

Confirmation

The findings confirm what UHMA Members have long known from years of practical experience.

"The tests were devised to clear up one of the last myths about underfloor heating," explained UHMA Chairman Rex Ingram who organised the research programme at BSRIA’s Bracknell laboratories.

"BS EN 1264 advises a maximum thermal resistance of just 1.5 Tog for any floor covering laid upon a heated floor. However, all experienced underfloor heating specialists know that it's possible to achieve full comfort conditions - and good response times – with the higher levels of resistance offered by some combinations of carpets and underlay.

In the past, carpet industry test results have focused only on how carpets work with radiators and air heating systems, ignoring how they work with underfloor heating. UHMA set out to discover what the facts really were!"

Most exhaustive research

The tests - which constitute the most exhaustive research into the subject ever - were carried out in liaison with The Carpet Foundation and BSRIA engineers in a test room built to the requirements of BS EN 442-2:1997. An

underfloor heating system topped with a 22mm floating chipboard deck was constructed in the room with sensors and measuring devices configured in such a way as to effectively create “single-plate” test conditions.

This system was used to test the thermal conductivity of some 19 carpet and underlay combinations at flow temperatures of 40, 50 and 60oC. Air temperature within the test enclosure was controlled to maintain 20oC at the central inner room reference point, which was 0.75m from the floor.

Convinced

Ingram is convinced the findings confirm that carpet and underfloor heating can work together perfectly well.

"Our tests showed that the tested combinations of carpet and underlay functioned as if they had a resistance of about 1.0Tog less than their combined published Tog values. As a consequence, it has been demonstrated that some carpet and underlay combinations with published Tog values of up to 2.5Tog have “real life” resistances that are within EN1264 guidelines.

However, it must not be assumed that the tests validate ANY carpet plus ANY underlay combination above a 2.5Tog combined resistance. The nature of their construction may determine their “real life” resistance over a heated floor. Some carpets and underlay have air layers and cells within their structure and this may increase the thermal resistance, because air is a poor conductor. Radiant heat can pass easily through these air spaces and this could explain the difference between the “real life” and published resistances.

Practical experience also suggests that as carpet "wears in with age", with its fibres being compacted by foot traffic and, as manufacturing “fluff” is vacuumed out, the resistance decreases even further. These factors – combined with the improved connectivity achieved by using double-sided tape or spray adhesives to fix the carpet - make possible even greater reductions in “real life” Tog ratings."

Other Articles