Underfloor heating: a buyer’s guide
How it works, the different options available and what costs are involved
Once used predominantly in kitchens and bathrooms, underfloor heating (UFH) is now an option for heating larger spaces, and even the whole house. As well as being pleasant underfoot, it also emits radiant heat, making it an energy efficient way to heat the home that works well with renewables.
‘One of the biggest attractions is that it’s completely invisible, with no need for radiators taking up your wall space,’ says Stuart Wisbey of the Stone & Ceramic Warehouse. ‘It is also particularly advantageous in spaces such as wet rooms, as floor moisture is quickly evaporated.’
Although there are many systems on the market, they all fall into one of two basic types – electric or water-based. An electric system, usually in the form of very thin wire or matting, works independently from central heating. A water-based system, on the other hand, is connected to the main central-heating source and works by circulating warm water through plastic pipes installed under the floor.
Water-based systems are an ideal whole-house solution. Electric systems offer easy retro-fitting for individual rooms and are cheaper to install, but cost more to run.
Electric underfloor heating (dry system)
Also known as a dry system, electric underfloor heating is installed directly under a floor covering and its low-profile has little impact on floor levels. It’s ideal for single-room installations, where a sub-level is already set. Loose wire systems allow for awkwardly shaped rooms, whereas self-adhesive mats offer the ultimate easy-fit solution. And it’s not restricted to use under floors; an electric underfloor heating system can be installed on a wall and seating in a shower and wet room.
All electrical connections must be made and tested by a qualified electrician in order to comply with building regulations. Because the heating element sits directly under the flooring, circuits are easily accessible if they need to be repaired. A disadvantage of this type of underfloor heating is that it can be more expensive to run than a wet system, and the Energy Saving Trust doesn’t recommend it for use in large areas. Roll-out heating mats start at £50 per sqm, and a loose-fit kit will cost from £100 per sqm.
Water-based underfloor heating (wet system)
A water-based underfloor system consists of a series of pipes connected to a boiler, which circulate warm water throughout the floor to heat a space. Generally used in new-builds or extensions, it is best suited to new floor constructions, which can be designed to hold the pipework and be adequately insulated. It’s ideal for an open-plan space or whole-house system, and can be fitted to a solar water-heating system.
A wet system can take longer to warm-up than other heating, but it also takes longer to cool down. A heating engineer or specialist will complete the water based underfloor heating installation, which can run to thousands of pounds if it’s a whole-property system. But problems tend to be extremely rare, and pipes are designed and tested to have a 50-year life expectancy. Just be aware that retrofit can be difficult, and floors may have to be elevated to allow for pipework.
Water-based underfloor heating systems are more expensive to install but cheaper to run in the long-term than electric systems. Expect to pay upwards of £100 per sqm.
How much does underfloor heating cost?
There are conflicting figures about the eco benefits and savings for under floor heating, depending on the type of piping laid and the insulation used. It can take a couple of hours to heat up a room using under floor heating, whereas a radiator might take only 20 minutes. However, radiators cool down a lot faster.
The key is to leave under floor heating on all day at a moderate temperature, such as 16°C, which requires less energy than a radiator would need to heat a room from cold.
An electric system can be more expensive, but a programmable timer – such as the 6iE Smart WiFi Thermostat by Warmup – can be used to optimise performance. Plus, as it runs independently from central heating, you can warm a specified area without having to heat the whole house.
Generally, under floor heating offers more than enough warmth to be used as a single form of heating, but its capabilities will be dictated by factors such as the floorcovering and building insulation levels. Your installer will be able to offer advice about looking into your home’s individual thermal performance, so you can calculate the amount of heat you need to generate. All installations should be tested before the floor finish is laid.
The price of underfloor heating depends on the system you choose, the size of the space you wish to heat, the desired heat output, how often your run the heating and how well-insulated your home is. But according to checkatrade.com, for installation you can expect to pay around £60-£85 for electric underfloor heating during a renovation (£50-£75 for a new build), and £135-£185 for water-based underfloor heating during a renovation (£120-£135 for a new build).
The Warmup website also offers a useful guide to system, installation and running costs.
Choosing your flooring
Underfloor heating is compatible with a wide range of floorcoverings, including carpet, providing the combined thermal resistance of the carpet and underlay is less than 2.5 tog. The thicker the product, the longer it will take to heat up and cool down.
‘The material needs to be expertly installed,’ says Jason Cherrington of Lapicida. ‘You have to wait for the screed to dry properly and then the UFH needs to be run to test it, as thermal movement can cause certain types to crack. Laying the floor tiles is relatively quick and shouldn’t take more than a day per 10sqm for a proficient tiler.’
Engineered boards are also a popular option among renovators and self-builders because they are less likely to warp. ‘It is one of the best materials for use with UFH,’ says Russell Calder at Havwoods. ‘Natural, warm to the touch and a good conductor of heat, the majority of engineered boards are perfectly suited for use with UFH. This is particularly true of those with a solid-oak lamella – the top layer of an engineered plank.’
Things to consider before installing UFH
- Underfloor heating is more efficient and cost effective if fitted above insulation, as it reduces downward heat loss. Ensure the rest of your house is well insulated, too.
- Stone, porcelain, slate and ceramic are compatible with underfloor heating, and have good thermal conductivity to provide a quality heat output. Thicker stone floors will take more time to warm up, but will retain heat for longer.
- If you’re looking for wood flooring, check suitability with your supplier, or consider engineered-timber boards.
- Most luxury laminates and vinyls are compatible, and you can also use carpet, providing that the combined thermal resistance of the carpet and underlay is less than 2.5 tog – check the details with the manufacturer.
- As a general rule, flooring that is compatible with underfloor heating can be used with both wet and electric systems.
- The expense may outweigh the advantages if you need to remove and rescreed a concrete floor to install a wet underfloor heating system.
- Choose a system that comes with an extended warranty as standard.