Underfloor heating
If you are considering installing underfloor heating, read Sophie Vening’s guide to how it works, how much it’s likely to cost and the installation process involved
How do you know which system is the best fit for your project? Sophie Vening explains how to decide
Underfloor heating (UFH) is often chosen because, as the name suggests, it’s hidden beneath your floor covering. This allows for clean lines and an open flow throughout your home that is uninterrupted by radiators. It also frees up wall space, which gives you the feeling of extra room, too.
UFH works really well with renewable technology such as heat pumps because it works at a lower temperature than a standard radiator system (around 27ºc-31ºc). This means an energy efficient setup and less demand on your boiler for a similar, if not better, level of comfort.
Wet vs electric systems
There are two types of underfloor heating to choose from – wet and electric. The latter is typically easier to install and is ideal for retrofit scenarios, whereas the former tends to be more complicated and costlier to fit. However, a wet underfloor heating arrangement works out more efficient and cheaper to run than the alternative.
A wet UFH setup features pipes filled with warm water. It is powered by a boiler or heat pump, which circulates the water throughout the floor to warm the space. This network is concealed within the floor structure, usually embedded within a screed. This helps keep the system in place and ensures the flooring surface is even.
The pipes are connected to your heat source via a manifold. The bigger the system, the more conduits you’ll have and the more complex the manifold is likely to be.
The arrangement will be fitted to a thermostat or multiple thermostats, depending on how many zones there are, so you can regulate the temperature.
Installing electric underfloor heating, on the other hand, avoids the need to raise floor levels in existing rooms.
This makes it a popular choice for use in small, awkward spaces that you want to warm, such as a bathroom or an ensuite. This type of system comprises matting, onto which cables connect into the property’s electrical circuit. The setup is then operated via a thermostat.
Installation know-how
A wet underfloor system should be fitted by a qualified professional, as it’s a complex process with plumbing connections and tests that need to be carried out.
The floor should always be properly prepared and insulated to ensure everything works efficiently. It’s why this system tends to be easier to lay in a new build, as these considerations can be made from the start of the design process. However, there are low-profile products available for renovation projects – more on this later.
There are also options available that incorporate a thermal protection layer into their design. For example, Polypipe’s Floating Floor System features high-density polystyrene floor panels that provide a base for the heating pipes and enhance insulation.
Retrofit options
It’s more complicated to install underfloor heating in an older property, as the system would raise the existing floor
height by nearly 150mm-200mm once you’ve added the screed, insulation and pipework, plus new floor covering. In reality, the floor would need to be dug out and relaid to accommodate the UFH and screed to the right level, thus making it impractical on cost grounds.
Thankfully, recent advances in technology have seen low-profile systems enter the market, which can be fitted directly on top of existing floors. Nu-heat has recently launched the Fastdeck, all-in-one, whole-house UFH and floor deck solution with a total height build-up of just 35mm. It can be installed either as a replacement for a screeded setup, or retrofitted over suspended timber and concrete surfaces. Alternatively, Nu-heat’s Lopro is available in three variations. It comes with a height buildup as little as 15mm, with optimum performance and high heat outputs, plus quick response times. Lopro Max in particular has an impressive heat output, ideal for properties with lower insulation levels or lots of glazing.
Wundagroup’s Wundatherm wet UFH offers a profile depth as little as 16mm, ideal for projects that require minimal height build-up. “This solution can only take a 12mm diameter pipe, which carries 57% less water compared to the 20mm design,” says Paul Simmonds at Wunda Group. “To combat the lower heat output, we made the conduit channel spacings smaller in the 16mm panel. They measure 125mm instead of the 150mm intervals in the 20mm boards. This means more tubing is required, but the optimum heat output is still achieved, despite the thinner profile depth and smaller pipe diameter.”
Something to note, however, is that installing UFH in an old and draughty house isn’t going to be the most efficient heating solution due to this technology’s lower running temperature. If you’re set on the idea, look to upgrade the building’s insulation and airtightness as part of the project.
Key considerations
Don’t forget to do your homework when it comes to specifying the floor covering that will partner your UFH. Tile, stone and polished screed are the best solutions. They absorb heat, rather than insulate, which allows warmth to radiate into the room effectively. Timber tends to create a thermally protective barrier and therefore reduces efficiency. This material is also likely to warp and cup when repeatedly heated and cooled. Engineered alternatives are more dynamically stable compared to real wood, and can work well. Interestingly, some carpets with an underlay of less than 2.5 togs can complement UFH, too. Always discuss the potential options with your installer before you buy. They will advise on which material is the most compatible with your chosen heating system.
Combining radiators with underfloor heating is another option to consider. Using both types of emitter can be the answer for many homes. A popular solution is to have
UFH on the ground floor, where people spend most of their time in the communal living areas. Radiators can then be used to provide short blasts of high output warmth upstairs, in zones that are not used as much throughout the day. Be aware that their need for higher temperatures normally means they need their own heating circuit.
The control system you use to operate your UFH is another element to bear in mind. Underfloor installations can take longer to warm up than radiators, so a userfriendly, programmable setup is essential. Smartphone apps mean you can manage your heating remotely. This is great for holiday homes or if you’re away on vacation, as you can switch everything on prior to your arrival so you’re greeted with a warm, comfortable environment.
Calculating the cost
According to Underfloor Heating Systems, self builders should budget around £12 to £14 per m2 for product supply, and between £5 and £6 per m2 for the installation of a wet underfloor heating setup. An electric arrangement will work out cheaper to buy and fit.
Rachel Roberts, technical account manager at Nuheat Underfloor Heating & Renewables advises a slightly bigger budget. “In a typical self build project, such as a detached three bedroomed home with a 100m2 floor area, you could expect a bespoke screed UFH system to cost approximately £2,800-£3,000 (£30 per m2), excluding the screed,” she says. “This would include a unique system design that is tailored to the property, the highest quality components and unrivalled customer support for the lifetime of the system,” she says.
“In a renovation project, like an average Victorian terrace with a downstairs floor area of 60m2, a bespoke Lopro10
setup would cost in the region of £4,000, or £65 per m2. This would include everything required to install the UFH so it’s ready for the chosen floor finish,” says Rachel.
She also advises that the cost of having the system fitted by a qualified heating and plumbing engineer is difficult to quantify. “The sum varies depending on the area of the UK and the size and type of UFH product being installed. If we consider a new build with a total floor area of 100m² and choose a professional who charges £30 per hour, you could expect it to cost roughly £800,” she says.