When heating a building adding underfloor heating is a very effective method to ensure that the space is heated evenly.
More and more underfloor heating systems are being fitted but the key question we are being asked about these is where the insulation should be positioned to make the most of the underfloor heating system. This will depend on if the underfloor heating system is intended to be run on a continuous low trickle or to have a quick heating response. We will look at both of these in turn.
There are several different methods of constructing a floor; either with a concrete slab, beam and block or a suspended timber floor. Insulation, such as Kingspan Kooltherm K103 Floorboard, can be used to reduce the heat lost from the room. A key factor in choosing the type of underfloor heating system for your floor construction is the thermal mass of the floor.
Thermal mass is the ability of a material to absorb and store heat energy.
Concrete has a high thermal mass – this means it takes a lot of heat energy to change the temperature of it. With a concrete floor the position of the insulation is important in either exposing the thermal mass of the concrete floor to the heat provided by the underfloor heating system or isolating the thermal mass from it. Timber has a low thermal mass and is better suited to an intermittent heating system.
Continuous Underfloor Heating
If you are considering a ground source heat-pump with underfloor heating as the heat emitter, where the heat source is a continuous low trickle, or a system with a 24 hour heating cycle then a concrete floor with insulation under the slab will be the best solution as the concrete will act as ‘thermal mass’ to release and regulate the temperature of the room above it. This will provide a more even heating regime over a 24 hour period.
Intermittent Underfloor Heating
The other option is to have a quick heating response to help regulate the room temperature. If this is the desired underfloor heating solution then there are a number of flooring options.
When the underfloor heating system is designed to run intermittently then, for a concrete floor, it is more effective to position the insulation between the floor screed and the concrete slab. This isolates the thermal mass of the concrete slab from the underfloor heating system, giving a quicker heating response as less thermal mass of concrete is available to take up heat from the system.
Suspended timber floors and beam and block floors also work best with intermittent underfloor heating. In these cases the insulation layer is directly below the layer which holds the underfloor heating system. This will ensure that the heating system works efficiently.
For more details about the different construction methods for floors and how they should be insulated, take a look at our Kooltherm quick guide.