Carpets are the traditional floor covering for bedrooms and living areas. It is perfectly possible to achieve good outputs with underfloor heating and carpet but some key points will need consideration. The combined value of the carpet and underlay should not exceed 2.5 tog, and preferably less than 1.5 for heat pump systems.
It makes sense to take care in choosing carpet and underlay that will work well with the underfloor heating. Quality manufacturers will have technical information on their products available to customers.
At the design stage, Nu-Heat’s unique Optimiser software program will consider the thermal resistance of the selected floor coverings to establish the quantity and spacing of heating tube required within each room. As a result, Nu-Heat is able to ensure that the necessary room temperatures can be achieved resulting in a comfortable heated environment.
The tog value of Brinton’s ‘Bell Twist’, a typical 80% wool and 20% nylon carpet, is 1.23. Most nylon pile carpets will achieve around 1 tog and the thickest wool carpet, over 2.5 tog. Accordingly, the thickest 80% wool and 20% nylon carpets should only be used after taking advice from both Nu-Heat design engineers and the carpet suppliers.
Consideration should also be given to the underlay used to ensure its tog rating is taken into account at the design stage – most suppliers provide this information.
Interfloor (manufacturers of Tredaire and Duralay) state that most of their underlay products are suitable for use with underfloor heating, Heatflow being specifically designed for the purpose.
Tredaire Technics sponge underlays with polyester facing and glass reinforced crepe paper backing have tog values of between 0.56 and 0.66 depending on thickness. Felt and heavy crumb underlays should be avoided.