Heat Pumps and Underfloor Heating

A heat pump supplying an underfloor heating system in a solid floor make-up is ideal.  Typical output for a heat pump should be between 40ºC to 45ºC.  In a solid floor make-up this works extremely well, however attention should be paid where the floor construction uses standard joists or batten.

Heat Pumps and Joisted Floors

In a joisted floor (without a heat pump), underfloor heating typically operates at 60ºC-70ºC.  While it is possible to get a higher temperature than 45°C from a heat pump, its efficiency suffers which reduces the benefits of the heat pump in the first place.

With a traditional joisted floor, a low temperature underfloor heating system would struggle to heat a room due to the thermal resistance of the chipboard.  To obtain maximum efficiency from a heat pump and underfloor heating where there is a joisted floor, IHS recommends the use of Lewis Plates.  Incorporating Lewis Plates allows for a screed pour over the joisted floor, which is ideal for use with a low temperature underfloor heating system.  The thermal transfer of the screed gives a far higher output, removes the need for chipboard and increases overall efficiency due to the higher thermal mass.  Further benefits of Lewis Plates include increased load bearing of the joisted floor, improved fire rating, and excellent sound absorption qualities.

The alternative to using Lewis Plates is to lay a hardwood floor throughout the joisted area, and increase the amount of underfloor heating pipe in the floor.  You might however struggle to achieve the output in the bathrooms where we would still recommend the use of Lewis Plates. (Bathrooms have a far higher heat requirement that other rooms).