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. Ask your installer about finding out the property’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.
Electric underfloor heating (dry system)
Also known as a dry system, electric underfloor heating is installed directly under a floor covering. It’s ideal for single-room installations, where a sub-level is already set. The wire or matting is very thin (about 3mm) and causes little disruption to the existing room. 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, but can get less expensive the more you buy. A loose-fit kit will cost from £100 per m.
Image: Stone & Ceramic Warehouse (020 8993 5545; sacw.co.uk)
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 have a slower warm-up time than other heating (depending on the system) but, on the plus side, 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. Prices start at just over £100 per sqm.
Image: Junckers (01376 534 700; junckers.co.uk)
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, director of Lapicida (020 3012 1000; lapicida.com). ‘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.’
Image: Havwoods (01524 737 000; havwoods.co.uk)
- 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, too, 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 UFH 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 UFH system.
- Choose a system that comes with an extended warranty as standard.