There are two options for safely heating carpeted floors and these both involve covering the heating element with screed or levelling compound to help it spread the heat evenly across the floor to avoid hot spots developing. We recommend using 160W heating mats or the 3mm cable system with levelling compound on top. Your carpet and underlay can then be laid on the screed or levelling compound. Be aware that the underlay should have a Tog rating no higher than 0.8 Tog, and the carpet no higher than 2.0 Tog. Most hessian-backed carpets have a Tog rating below this. Thermal underfloor insulation boards installed beneath the heating system will increase warm up time and reduce running costs.