Retrofit UFH

Customers are increasingly looking at energy efficient solutions for their heating needs. In a new-build scenario there are many options available, but how can low carbon and renewable technologies work with existing properties? Adrian Troop, Nu-Heat’s Sales and Marketing Director discusses the reality of retrofitting underfloor heating and how it can be future-proofed for use with a heat pump. 

There is no doubt that retrofitting underfloor heating (UFH) can present major challenges, but this is not a reason to dismiss the technology. Having said that, it is vital to ensure that a property is suitable – there is no point fitting the system if it won’t work properly.

There are minimum requirements regarding insulation. The existing property should be brought broadly in line with the requirements of Part L of the Building Regulations; wall insulation, double glazed windows and doors are all helpful. Floor insulation is essential and could affect floor height build-up. A good UFH supplier will undertake full heat-loss calculations and advise where shortfalls, if any, will be.

Floor constructions

There are three standard floor constructions available: floating floor, suspended timber and screed. Screed is better suited to new-builds, extensions and conservatories due to an average floor height build-up of 150mm and renovation projects where floors are being removed or sufficient height is available.

Overall we found working with underfloor heating very straightforward. Information was readily available and it helped that we had an installer that was keen to learn new skills

Paul Pulman of Pulman's Builders

For retrofit, suspended timber floors have little impact on floor height build-up, although ceilings or floors will have to be removed in order to lay the floor heating tube. This is fine if they are being replaced anyway but if they have to remain in-situ a floating floor is a better solution. The floating floor construction is a popular option for retro-fitting UFH as it benefits from minimal floor height build-up and is straightforward to install, laying over the existing deck.

One example of successful UFH retrofit is the conversion of two derelict farm buildings into three holiday cottages with eco-friendly, cost-effective heating. The biggest challenge for contractor Paul Pulman of Pulman’s Builders was to maximise the available internal living space within the existing footprint. Underfloor heating (UFH) was recommended as usable room space would be increased by up to 15% by removing the need for radiators.   

On the first floor, Paul utilised Nu-Heat’s aluminium ClippaPlate™ which is self-supporting and only needs a couple of screws to fix in before tubing is clipped into place, making installation faster and safer.

For this project, UFH was integrated with air source heat pumps (ASHP), a combination offering long term ecological and financial benefits.

Future proofing UFH for heat pump technology

It is possible to install UFH on its own with view to changing to heat pump technology at a later date, but if this is the case, the cost of future-proofing UFH at installation stage will be far less than attempting to change everything when the heat pump is installed. An experienced design and supply company will ask the relevant questions to ensure that the final system will work equally as efficiently with a boiler or heat pump.

Major considerations

It is possible that more pipe may be required for use with a heat pump due to the lower water temperature. For example, pipe spacing for a conventional boiler might typically be at 200mm centres and a heat pump at 150mm centres. With so many variables such as room size, glazing and floor covering, the spacing can only be properly determined at the design stage.

The choice of floor covering will also have an impact, and it is important to know what will be used when the heat pump is installed. Most tiles, slate, laminates and solid wood coverings work well with UFH. Carpet and underlay are acceptable as long as a tog of more than 2.5 is not used. 

For any UFH installation, levels of insulation are essential to the efficiency of the system, but when a heat pump is to be used this is even more critical. Insulation levels should ideally ensure that less than 45 watts of heating are required per square metre of floor space. 

It is also vital to see if the installation needs of heat pump technology are practical in a particular property. For example, an area approximately two and a half times the size of the property is needed for laying the ground loops for a ground source heat pump. An air source heat pump requires space outside, pipework and wiring from the external unit back into the property and both types of heat pump require internal space to house the cylinder, buffer tank and other equipment. 

It is possible to install UFH both in retrofit and for future use with a heat pump within certain parameters. Once a good design and supply company has the project details they should give frank and unbiased advice on feasibility.

	Published: 27/07/10
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