Underfloor heating can be completely hidden unlike bulky radiators, is efficient and toe-warming but which, if any, system is right for your home extension or room renovation?   

What are the benefits?

Underfloor heating can add value to your property. It is associated with luxury and high-end fittings. In the winter months, what could be more luxurious than a warm floor as you step out of your bed in the morning?  Aside from cosy toes, there are other benefits to a heated floor. In a conventional heating system, the hot air from radiators rises. While temperatures at ceiling level could be almost tropical, floors remain icy. One significant plus of underfloor heating is that heat is distributed more evenly around a room than with radiators, so fewer cold spots.

It’s hidden underfloor, so there’s less space taken up by ‘dust traps’ radiators, making rooms less cluttered and easier to clean. A well-installed and insulated underfloor heating system works at a lower temperature compared to a traditional radiator setup, reducing heating bills.

So, what’s not to like?

A major drawback is that installation is typically more expensive than a standard central heating system because it’s embedded under the floor. Depending on the system, it could mean removing and replacing the existing floor structure. This means even if your heating bills are lower, you’re unlikely to recoup your investment.

Also, on the downside, it takes longer to heat up and cool than radiators. A concrete floor can take two to three hours to warm up to the required temperature and a timber floor 30 minutes to an hour, whereas radiators are almost instantaneous.  It could take 24 hours to heat up a room from stone cold. Similarly, cooling time can be lengthy. A programmable timer and thermostat are essential to overcome this problem. Electric underfloor heating can be quicker to heat up than water-based systems but is usually more expensive to run.  Underfloor heating should not be fitted under floor mounted units. This may restrict where you place furniture and fittings. 

Warm water: buried

Underfloor heating dates back at least 2,000 years to the Romans. The stone floor of a villa was raised on brick piers and hot air from wood fires circulated below.  Modern underfloor heating uses either hot water flowing through pipes or electrically heated cables. In a ‘wet’ system the pipes which are connected to the boiler are buried in screed, a type of cement, and insulated so the heat flows up and not down.

A water-based system is generally regarded as the most energy-efficient way of delivering underfloor heating and has low running costs.  However, it requires space for pipework and could involve the floor being raised, so is best suited to new-builds or extensions.

Warm water: surface mounted

Fortunately, options have increased for home improvers who don’t want the hassle of digging up their floors. It’s possible to buy insulated panels with routes channelled out for pipes to sit in, which can be laid on top of your existing floor. The low-profile panels add about 1.5cm to the floor height.  Warm water is circulated in a similar way to the buried system. The downside is it’s relatively expensive and can cause floor level changes between rooms.

Electric

In an electric underfloor system, a series of wire coils or electric mats are installed beneath or within the floor. As this system is powered by electricity, there’s no need for a boiler. Options include loose-fit wiring flexible enough to fit into small or awkward spaces and cables woven into a mesh mat for easy installation. The ready-to-roll electric underfloor mats are slim and can be laid within tile adhesive, making them popular for bathrooms. The electric systems are easier to retrofit and cheaper to install. This system is great for renovations as it won’t raise floor levels. However, the running costs are higher than water-based systems, so better suited to small spaces.  

Installing underfloor electric heating

Most people employ a professional company or supplier to install underfloor electric heating. Experts are best placed to advise you on the most suitable system and how to prepare the floor. If you’re a confident DIYer, it’s possible to lay electric underfloor heating mats yourself. But you’ll need a qualified electrician to wire the electrical system to the mains supply. A water-based system is much more complicated to install. If you’re doing it yourself, your supplier should provide pipework drawings. All installations will need to be tested before the final floor finish is laid. You will need a professional plumber to connect a wet system to your boiler.

How much does underfloor heating cost?

Prices are around £50 to £90 per metre2  for electric mats - prices correct in November 2018. In addition, you will need to add the costs of screed, insulation board and heating controls. Remember you’ll need to pay a qualified electrician to link it to your electricity supply.

A water-based system is more expensive to install than an electric one as it involves laying pipes and plumbing connections. Expect to pay upwards of £120 per metre2 Costs will vary depending on individual circumstances, such as how far it is to the boiler.

How does it cut heating bills?

Underfloor heating is typically more energy efficient than radiators and less expensive to run.  This is because the system can use water at a lower temperature than radiators. The temperature of a heated floor surface is around 29C for a solid floor or 27C for a timber floor compared to 65C to 80C for a radiator. If a room is properly draught-proofed and insulated, this may be enough heat to keep it warm. But if not, you may still need radiators. Underfloor heating is even more efficient when teamed with a modern condensing boiler or heat pump.

What types of flooring are suitable for underfloor heating?

Underfloor heating can be used with a variety of floor types – stone, tile, timber and even carpet. Solid floor surfaces are often the most suitable floor covering, including terracotta, porcelain tile and slate. If you opt for timber, check with your supplier it’s suitable to use with underfloor heating as surface temperatures shouldn’t exceed 27C. Engineered timber boards tend to be more stable during temperature changes due to their construction. Some higher quality laminates, vinyls and carpets can also be used with underfloor heating but not all, so double-check. Remember, heat output may be slowed by thick carpet and underlay.  Adding insulation under the pipes or electric cables is extra cost but essential to direct the heat upwards.

Underfloor heating is suitable for many different types of projects from retrofits to refurbishments and new extensions. Ask an expert to make sure you get the correct system for your building project.