Underfloor Heating and Floor Insulation

Insulating a concrete floor

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.

Floor Constructions
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 K3 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

K3 - concrete floor - insulation below the slab with underfloor heating

Concrete floor – Kooltherm K3 insulation below the slab with 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

K3 - concrete floor - insulation below the screed with underfloor heating

Concrete floor -Kooltherm K3 insulation below the screed with 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.

 

K3 - suspended timber floor - insulation with underfloor heating

Suspended Timber Floor – Kooltherm K3 insulation with underfloor heating

K3 - beam and block floor - insulation underfloor heating

Beam and Block floor – Kooltherm K3 insulation with underfloor heating

 

 

 

 

 

 

 

 

 

 

For more details about the different construction methods for floors and how they should be insulated, take a look at our structural quick guide.

To keep up to date with all our latest blog posts you can follow the blog by clicking this RSS Feed link or by following us on Twitter @KingspanIns_UK or on Linkedin.

Share this blog post with your friends and colleagues by clicking on the social media icons below.

Print this page

Kingspan Insulation is a market leading manufacturer of optimum, premium and high performance rigid insulation products and insulated systems for building fabric and building services applications.

0 comments on “Underfloor Heating and Floor Insulation
  1. I have under- floor heating over a suspended timber floor.Would there be any advantage in insulating the underside of the timber floor perhaps between the joists, access is quite easy.

    • Hi Mike,
      Thank you for your question. The simple answer is ‘yes’. It would be beneficial to have insulation between the joists to prevent heat being lost unnecessarily to the ventilated void below. Have a look at our U Value calculator to work out the thickness you need: I’ve done some of this for you…

      Peter

Leave a Reply

Your email address will not be published. Required fields are marked *