Thermal Primer is an energy star approved product that creates a small thermal barrier between the underfloor heating system and the subfloor below. This barrier helps reduce the amount of heat soak into the subfloor, meaning more of the heat rises through the floor into the room. Thermal primer is an easy way of reducing the running costs of your underfloor heating system. Thermal Primer also acts as a PVA alternative when used with Tile Adhesive, so when choosing this option the Mira primer is not required. Enough Thermal Primer is provided to provide 2 coats, this provides the maximum benfits.