Without a thermal break, the concrete acts as a heat sink. Therefore, the heat is drawn first into the concrete sub-floor before your floor covering. This is why Warmup recommends installing Warmup Insulation Boards over the concrete sub-floor to act as a thermal break. This forces the heat radiate upwards first rather than down into the concrete slab. Warmup insulation boards can increase ramp up time by over 70% and decrease heat loss by over 90%.