Retrofit Underfloor Heating

What is retrofit underfloor heating?

Underfloor heating, especially a wet or water-based heating system, is typically installed in a new-build property or the extension of an existing property. That’s because a wet underfloor heating system involves extensive installation of pipework, including valves, manifolds and a pump. It’s much easier and quicker to install this type of underfloor heating system when the property is empty and before the flooring surfaces are laid down. 

Retrofitting underfloor heating can cause major disruption, as in some cases, the existing floor surfaces may have to be lifted to install the pipework and insulation. Should retrofitting underfloor heating be the preferred option then it would be best if the property is vacated during the installation work. However, there are other, easier options you might want to first consider.

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.

There are several factors you need to take into consideration when deciding if a retrofit underfloor heating system is right for you. This includes the condition of the existing floor surfaces. For example, a stone, tiled or concrete floor must be sound and level, otherwise, a levelling compound will need to be applied. Timber floorboards must be free from rot, otherwise they will have to be replaced. Floorboards also need to be level although a levelling compound can be added as part of the preparation work.

Other aspects to consider include existing insulation. underfloor heating is at its most efficient when a property is fully insulated. Next, compare overall installation and running costs for both electric and water underfloor heating systems. Are you able to reduce running costs by having a heat pump or solar panels installed? Should you include a thermal store? Costs relating to thermostat and control options can vary too. Some older properties, such as those built from solid stone and without wall cavities are not suitable for 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.

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.

FAQs

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.