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Retrofit underfloor heating

Retrofit Underfloor Heating

Learn about retrofitting underfloor heating and what it'll entail

Retrofitting Guide

Have you ever considered having underfloor heating installed in your home? Retrofitting underfloor heating involves laying down underfloor heating after the flooring of your home has already been placed. Not all properties are suited for retrofitting and, in some circumstances, existing subfloors may have to be lifted, causing major disruption. However, due to advancements in technology, it is now possible to lay underfloor heating efficiently and effectively on top of most types of existing flooring. 

In this article you’ll learn about retrofitting both water and electric underfloor heating systems and what that entails, the advantages and disadvantages of retrofit underfloor heating, and the all-important installation costs involved.

Types of retrofit underfloor heating systems

  • Retrofit electric underfloor heating

    Retrofit electric underfloor heating could be the answer should you not wish to move out of your home while underfloor heating is being installed. Electric underfloor heating can be quickly fitted to an existing property, causing much less disruption. Floorboards may still need to be lifted if you want to keep the same floor height, otherwise, the underfloor heating matting and electric cables can be laid on top of any existing surface, including concrete. Most of the work can be carried out by a DIY enthusiast although connecting the system to the mains electricity supply is best carried out by a professional electrician.

  • Retrofit water underfloor heating

    A retrofit water underfloor heating system is slightly more labour-intensive and time-consuming. It also involves many more components than an electric underfloor heating system. For that reason, it is much more expensive to install but it’s still cheaper to run in the long term. Water underfloor heating system technology has improved significantly over recent years, allowing this type of heating system to be installed on top of most existing floor surfaces. It can also be connected directly to an existing heat source, such as a gas boiler or heat pump.

  • Overlay underfloor heating

    Overlay underfloor heating is an extremely versatile system that can be considered for most floor surface types, especially those that cannot be easily removed. For example a concrete or stone kitchen floor. Overlay underfloor heating consists of a series of grooved panels, which are simply laid or fixed onto the existing floor surface. Overlay panels are best used for water underfloor systems, with grooves ready to thread through pipes. With overlay underfloor heating kits, the floor level is raised by just 15mm and installation time is considerably reduced, making this option ideal for most retrofitting underfloor heating projects.

  • Low profile underfloor heating

    Another specially designed system for installing underfloor heating in existing house projects is low profile underfloor heating. This quick and easy system makes use of low profile groove boards, which raise the floor height by just 16mm. A low-profile underfloor heating system can be custom-designed for rooms of any size and because no screed is involved, tiles and laminate floor surfaces can be laid directly on top. For other floor coverings, such as carpet and vinyl, a levelling compound will need to be added to the subfloor. A range of water low profile underfloor heating kits are available.

How much does retrofit underfloor heating cost?

Retrofit underfloor heating installation costs will depend on many different factors such as the type of underfloor heating system you want to install, the number of rooms to which it will be installed, and the type of heat source available. The cost of retrofitting to an existing and occupied property would be considerably higher than installing as part of a renovation project or to a home extension. A water underfloor heating system installation will certainly be more expensive than an electric underfloor heating system. However, other costs you should seriously consider include annual running and maintenance costs.  

Water underfloor heating, although more expensive to install, is more economical to run and should last at least 50 years. An electric underfloor heating system is quicker and less expensive to install but more costly to run and will last about 25 years. Here is a quick guide to installation and running costs for both systems.

Water underfloor heating system: *Expect to pay on average between £120 and £135 per m² for a new build property and between £135 and £185 per m² for a retrofit project. Average running costs are £2.10 per hour.

Electric underfloor heating system: *Expect to pay on average between £50 and £75 per m² for a new build property and between £60 and £85 per m² for a retrofit project. Average running costs are £2.90 per hour.

More information can be found in our underfloor heating cost guide.

Advantages of retrofit underfloor heating

There are obviously advantages and disadvantages to retrofit underfloor heating. Some of the benefits include:

1. Energy costs – replacing a gas boiler with a heat pump can lead to more savings in the long term.

2. No more radiators – plus more room space and no protruding pipework. It makes decorating a lot easier too.

3. Electric underfloor heating systems are virtually maintenance-free and quick and easy to install.

4. Both water and electric, low profile and overlay systems, can be installed on top of existing floors with only a minimal rise in floor height.

5. No more dust allergies – The low surface temperatures of underfloor heating mean less air turbulence and therefore fewer allergens circulating in the air. Underfloor heating also virtually eliminates the causes of mould on walls and around windows.

Disadvantages of retrofit underfloor heating

Of course, every heating system will have its disadvantages and these include:

1. Retrofitting an underfloor heating system can be costly and disruptive but the savings in energy costs can be considerable, especially if the heat source is a heat pump.

2. Some floor coverings are not suitable for underfloor heating systems, especially thick pile carpets. However, there should be no need for thick carpets with any underfloor heating system.

3. Underfloor heating systems have a slow heating-up time when compared to radiators so you will need to adjust the time clock thermostat accordingly.

How to retrofit underfloor heating

If you’re seriously considering a retrofit underfloor heating installation then here’s what you can expect. 

First, your property will need to be assessed to ensure it is suitable for a retrofit procedure. Some old stone-built houses and cottages are not suitable. The property will need to be suitably insulated to specification BS EN 1264-4.

Consider whether the floors will need to come up or whether you can have the underfloor heating laid on top of existing subfloor surfaces. Whatever the circumstances, you can expect a degree of disruption throughout the process. Also, remember the floor could be raised by around 15mm.

It’s advisable to get professional advice about what is the best system for your home, based on your budget and preferences. You can save some money on installation costs if you are able to carry out some of the work yourself. However, connecting the system to the mains water or electricity supply should be left to a professional.

Consider the final floor covering. Underfloor heating is suitable for a wide range of floor types including, tile, stone, vinyl and laminate, timber and carpet.

How to insulate retrofit underfloor heating

Heat can travel downwards, upwards and also sideways so you should consider whether your retrofit underfloor heating system will need insulating. First, consider the insulation of your loft and walls. Next, if the floor has to come up for the underfloor heating installation then there will need to be some insulation fitted beforehand. Existing timber flooring, which is suspended on beams, will need to be insulated before laying any type of underfloor heating system. Stone or concrete floors do not need insulation as these materials have minimal downward heat loss.

Suitable insulation products for retrofit underfloor heating include mineral wool, insulation boards, polystyrene, sheep wool, aluminium floor foam and foil. Any existing insulating material can be replaced with one of the above products, if necessary.

Frequently Asked Questions

Can you retrofit underfloor heating?

Yes, you can retrofit underfloor heating, provided the property is suitable and the subflooring is in good condition.

Do I have to dig up my floor for underfloor heating?

No, you do not have to dig up your floor for underfloor heating. Very often, modern underfloor heating systems can be installed on top of an existing floor with minimal disruption.

Can I add underfloor heating to an existing system?

Yes, you can add underfloor heating to an existing system. Underfloor heating can be connected to an existing gas boiler or heat pump or connected to the mains electricity.

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