Should Underfloor Heating be Considered for Upper Floors?

Underfloor Heating

The question?

You have a project, be it renovation or new-build and are considering upgrading to the luxury of underfloor heating for the ground floor as you know that it is a sign of quality but should you also be considering it for the upstairs?

The use of underfloor heating upstairs is becoming more common, but an understanding of the advantages this brings could be helpful in making decisions...

 

Underfloor Heating from below

Efficiency of the heating system

Perhaps the most compelling reason for using underfloor heating within a concrete or screed is the effect it has on the efficiency of the heating system, whether it be a conventionally fueled or renewable energy based one.

Underfloor heating should only be considered when the insulation and airtightness of the building has been addressed and is sufficient to ensure this type of heating system is suitable.

Typically the temperature of the water within a traditional radiator based system is around 65-75oC, compared to 35-45oC in the pipes within a typical concrete or screed floor (please use the terms concrete and screed interchangeably for the purpose of this post).

By decreasing the temperature of the water produced by the heating system, less energy is required to provide the heating to a building.

This is great for the ground floor as it is generally relatively simple to have a concrete ground floor.

Upper floors are typically made of timber and therefore require a suspended under floor heating system, these can be based on the pipes being installed under a traditional timber deck, usually tongue and groove, chipboard or plywood boards. Timber boards understandably act as an insulation layer and therefore a higher temperature is again required, often back up to the 65-75oC range, making this type of system often no more efficient than radiators.

Ideally to get the same efficiency as a concrete ground floor it makes sense to use concrete at first floor and above.

The introduction of the Renewable Heat Incentive (RHI), increasing performance requirements of Part L of the Building Regulations and the Government’s drive to see all new buildings built to Zero carbon standards within the next few years will see a rapid rollout of heat-pump systems. These are ideal for use with under floor heating as they efficiently produce heat at the lower temperatures associated with underfloor heating.

It’s understood that where underfloor heating is used on the ground floor and radiators on upper floors the heating system will be required to produce higher temperature water for the radiators that is then blended with colder water for the ground floor, thus detrimentally affecting the efficiency of the system, especially where heat-pumps are involved.

Therefore to maintain the efficiencies of a heat-pump system it is sensible to link the system to under floor heating on all floors.

Thermal mass

Many of today’s buildings are constructed using lightweight materials, be it light weight blocks, timber frame, light gauge steel frame or SIPs or using techniques that effectively isolate the thermal mass from the interior of the building, for example ICF or plasterboard linings mounted on battens or “dot and dab” effectively introducing an insulation layer of polystyrene or still air between the internal atmosphere and the material that has the mass.

Thermal mass helps to buffer heat losses and gains, heat loss in the winter and overnight and solar gains in the summer, making for a more comfortable internal environment without spikes in temperature, up or down and the resulting affect this has on the occupants and how hard the heating system has to work.

By introducing thermal mass into the project in the form of concrete floors into any of building systems mentioned above enables this buffering system to assist in regulating the internal temperature.

To get the best out of the thermal mass and an underfloor heating system, appropriate floor coverings should be chosen, the denser the better, including all types of tile, dense timber, polished concrete, carpets and underlays designed for use with underfloor heating, etc.

Space

Incorporating underfloor heating eliminates space consuming radiators and their effect on room layouts. Radiators should not be placed under windows as, even with triple glazing, these will be the worst performing areas of the wall and people often have curtains that extend right to the floor, this allows a lot of the heat generated to escape. Having radiators on other walls will always then compromise the choice of placing furniture.

In discussions with an architect recently, it was estimated that the use of radiators effectively reduced the useable space within a room by about 10%. For self-builders, this means that by using under floor heating, their rooms are effectively bigger for the same foot print and for developers, their footprints could be reduced but they would still be offering the same useable area for each room, this benefits both type of builder.

The efficient utilization of space is vitally important in many other types of buildings, including: apartments, student accommodation, hotels, motels, care homes, etc.

Education

The use of any underfloor heating system requires a change in thinking about how the system operates as they tend to have longer heating up and cooling down periods. This necessitates patience and understanding of how the system best works.

A properly programmed, zoned thermostat controlled heating system will ensure that rooms are very comfortable during the course of the day and night. This is especially the case with heat pumps that work most efficiently over longer periods and are therefore ideally suited to underfloor heating.

Summary

With the continued increasing uptake of under floor heating, especially in conjunction with heat pumps, the case for taking it “upstairs” needs to be defined. This is not just down to the practicalities of how to install the pipes, but also what the effects are on the efficiencies of running the building and how this fits with the continued tightening of regulations to make buildings of all types more efficient.

Being able to easily install a concrete floor upstairs is key to ensuring the best efficiencies are achieved from any heating system chosen to be combined with underfloor heating.

About the author: Chris Holt is the MD of CDI Innovative Construction Materials Ltd, which brings Lewis® Decking to market to create concrete or screeded suspended underfloor heating, acoustic, wet-room and fire-proof floors. He is also a BRE registered Code for Sustainable Homes Assessor.

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