Can Air-Source and Ground-Source Heat Pumps be used with Underfloor Heating?

The short answer is, YES – in fact they compliment Underfloor Heating (UFH) perfectly, although there are a few factors that need to be considered.

The reason that UFH works well with heat pumps and is more efficient, is that it requires a much lower flow temperature than traditional heating systems. Radiator heating systems typically work on a boiler flow temperature of 70-80 degrees, but UFH requires much lower flow temperatures – normally in the region of 40-50 degrees, which is typically the range of flow temperature that a heat pump offers.

Heat Pumps and UFH – the design process

It is very important that any parameters specified by the heat pump manufacturer are incorporated into the UFH design. Ambiente offers a full CAD design service, taking into account any specific requirements of the chosen heat pump.

The design of a UFH system is based around several input parameters:

• The fabric heat loss of the building to be heated
• The manifold location
• The size of the UFH pipework installed
• The spacing between each run of pipework installed
• The flow temperature provided by the heat source
• The room design temperature (the target temperature we are trying to achieve)
• The proposed floor coverings in each area
• The external weather conditions

One final factor to add to the above list is the selection of the actual type of UFH system to be installed, which will be largely governed by the floor construction in the area to be heated. UFH systems for different floor constructions will vary in their heat output capability, which is all taken into account in the design process.

The most accurate way to make sure that UFH will adequately heat a room, is to work back from the heat loss figure – this is the actual heat loading that will satisfy the building heat loss, at worst-case external weather conditions. Room-by-room heat loss calculation would usually be calculated by a mechanical consultant; these can then be compared to the heating output to make sure that the UFH is providing adequate heating to each area.

How does the UFH system differ, when used with a Heat Pump?

The UFH system in conjunction with a heat pump will be made up of the same components, the only real difference is that because the water will be supplied directly to the manifold at a relatively low temperature, there will be no additional need to blend the water at the manifold – so no need for a local blending valve.

Some heat pumps will have sufficient pumping capacity to circulate the water around the entire UFH system – this point will need checking at design stage, to see if the supply of an additional local manifold circulation pump will be necessary.