Find out the difference between warm water and electric underfloor heating (UFH), how UFH can affect your energy bills, whether you can install it yourself, what type of flooring you should lay over it and much, much more.

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The cost

You can expect to spend upwards of £100 per square metre for wet systems and from £50 per square metre for electric, excluding floor preparation, underlay and installation. Although electric systems are more expensive to run than wet systems, programmable timers can help cut costs. Compared to a radiator-only system, UFH is estimated to be 25 per cent more efficient when paired with a modern condensing boiler, and up to 40 per cent  cheaper when combined with a heat pump.

Wet vs dry systems

As electric systems are installed directly under the floor covering, and work independently from your central heating system, they are particularly useful for one-room installations or where the sub-floor level is already set. The wire or matting systems are very thin (around 3mm) and shouldn’t cause problems with differing floor levels – thus creating little disruption to the existing room.

Wet systems circulate warm water through plastic pipes installed underneath the floor and are connected to the main central heating source. This system tends to work best when the pipes are embedded in a screed, as this helps dissipate the heat, so it is suited to new floor constructions where the sub-floor can accommodate the pipework and cement screed. Wet systems are therefore more likely to be used in new-builds and extensions or during major renovation work.

Martin Conway, technical services manager at Pimlico Plumbers
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Can I retrofit underfloor heating?

Electric underfloor heating may be installed on all existing subfloors when renovating a room or house. Virtually all floor surfaces can be heated including laminate, vinyl and wood.

An electric underfloor heating system is usually composed of a either a heating cable or a mat with a pre-spaced cable together with a thermostat for the zone. Ultra-thin 1.8mm heating cables are available on the market along with 3mm mats so the system should not affect your floor height. With no pipework, no maintenance, a lifetime warranty and highly efficient zone control of heating, electric underfloor heating is exceptionally good value to install and run.

A 3m² bathroom heater can be self-fitted and installed for less than £250 and cost £20 each year to run.

Remember to get a heat loss calculation done prior to buying a system to ensure the efficiency of your home. The key is to check that the heat output of underfloor heating is higher than the heat loss of a room.

Andrew Stimpson, CEO of WARMUP PLC.

Warmup sticky mat underfloor heatingThe Sticky Mat electric underfloor heating system from WARMUP PLC. with pressure sensitive adhesive for speedy, low-profile installation. From £48.92/m² exc VAT

Efficiency

Wet underfloor heating (UFH) systems generate temperatures of around 40°C to 65°C, meaning that the actual floor temperature will be on average between 23°C and 32°C. This is actually lower than a standard radiator, so your household heating costs should be reduced over time.

Electric systems may prove a little more expensive when directly compared with a wet system. However, programmable timers can be used to optimise performance and, as electric UFH works independently from the central heating system, this allows you to warm a specified floor, without having to heat the entire house and waste energy.

‘You also need to take into consideration the initial low cost of installing an electric system, against the higher installation cost of a wet system.

Royden Evans, managing director of PlumbNation
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Ease of control

Specialist UFH controls are vital to ensure comfort, responsiveness and energy efficiency. UFH takes longer to heat up and cool down compared to radiators, so to overcome this time lag, programmable controls are essential.

For households with irregular or limited occupancy and for holiday homes, it is useful to have remote control so that you can turn it on an hour or two before arriving. Remote control is also useful if you forget to turn the heating off.

Michael Holmes, experienced renovator

Getting the right insulation

Underfloor heating will always be more efficient and cost-effective when fitted above insulation, as this reduces downward heat loss and forces heat up into the room where it is wanted. In new-build homes and extensions, floor insulation will be incorporated to meet Building Regulations, while on refurbishment projects insulation can usually be added.

Taking up existing floorboards to add insulation between the joists is fairly straightforward. Adding insulation to a concrete screed floor, however, will mean that the height of the floor is increased so skirting boards and doors will have to be adjusted accordingly. We always recommend speaking to a reputable company, as they will be able to offer advice based on the individual characteristics of your home.

Chris Weightman, senior development engineer at Nu-Heat
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stone-works-well-with-underfloor-heating
  Check the tile thickness before you match them with underfloor heating. The maximum floor temperature for tiles should not exceed 27°C to avoid damage to the flooring

The installation process

Electric underfloor heating systems can easily be installed by a competent DIY-er, although the majority of projects are still completed by a contractor, such as a tiler or electrician. If you’re tackling it yourself, always follow the instructions accompanying the product, and remember that all electrical connections must be made and tested by a qualified electrician in order to comply with Part P of current Building Regulations.

Wet systems are invariably installed by professionals. However, kits containing everything you need are available. Your chosen company should conduct a full heat-loss calculation of the room/s and provide pipe layout drawings for you to follow, along with installation manuals bespoke to your needs. A qualified installer is needed for electrical or gas connections. All installations, whether wet or dry, should be tested before the final floor finish is laid.

David Perl, managing director of Cosyfloor
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Tiles work well in the bathroom with underfloor heatingTiled floors are ideal for use with UFH due to their low thermal resistance and high thermal mass. Hexagon floor tiles, from £29,95 per m2, and Mono Patchwork wall tiles, £49.95 per m2, both Walls and Floors

Choosing flooring

Solid floors, including stone, porcelain, ceramic, terracotta and slate are ideal, as they tend to have great thermal conductivity and will provide good heat output when it comes to underfloor heating. If you prefer timber flooring, always check with your supplier to ensure it is suitable for use with underfloor heating, or consider engineered timber boards that, due to their construction, tend to be more stable during changes in temperature.’

In both cases, bear in mind that temperatures shouldn’t exceed 27°C. Most top-of-the-range laminates can also be used with underfloor heating, as can all carpets — although you may find heat output is slowed down a little, due to the combination of carpet and underlay.

Ian Paton, home world interior buyer at Homebase
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Potential faults

The main cause for concern for many prospective buyers of warm water underfloor heating is what to do if the pipes leak. However, unless a nail is accidentally put through them at some stage, this simply does not happen. There are no joints in the floor and the various pipes used are designed and tested to have a 50-year life expectancy at temperatures and pressures that exceed those required by the system.

If accidental damage should occur, then individual pipes can be pressure tested to locate the correct one. In timber floors, the pipe can usually be exposed to allow for repairs, while screed floors will need to be excavated to uncover the pipe. When it comes to electric systems, the heating element often sits directly under the floor so it is simply a case of lifting the floor covering and replacing the damaged circuit.

Chris Ingram, chairman of UHMA (Underfloor Heating Manufacturers Association) 
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 Installing-underfloor-heatingIf you’re installing underfloor heating at first-floor level and won’t be laying screed, you can use a steel Lewis Deck as a base. This helps spread the heat quickly across the whole of the floor and further improves its efficiency. Expect to pay from £20 per square metre for Lewis Deck, excluding installation and the UFH system

Choosing the right system

It’s particularly effective for large open-plan spaces – particularly those with high ceilings – as the entire floor radiates heat upwards so you benefit from warm feet and even room temperatures. This radiant heat also means reduced draughts, moisture levels and airborne allergens.

Typically underfloor heating is more than enough as a stand-alone form of heating. However, its capabilities will often be dictated by other factors, such as floor coverings and a building’s insulation levels (especially walls and windows). This is why heat-loss calculations are so fundamental, as having looked at a building’s individual thermal performance they will tell you how much heat you need to generate.

For example, a poorly insulated room with lots of glazing may not heat fully when it is cold outside (which means additional insulation or supplementary heating may be necessary). Floor coverings also play an important role. Normally, stone and tiles are excellent options, as are carpets with suitable tog ratings. If you’re keen on timber, however, remember it has a lower temperature tolerance.

Bob Sage, head of operations at Robbens Systems 
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Underfloor heating vs radiators

Where cost is an issue, the expense of installing underfloor heating may outweigh the advantages, especially if it involves removing concrete floors and re-screeding. In houses not occupied during the day, underfloor heating’s slow warm-up and cooling time (which can be up to four to six hours) may not suit you.

‘A combination of both systems can often be the best answer for many homes, as radiators can be easily incorporated into an underfloor system. A good compromise is to install underfloor heating on the ground floor, with radiators upstairs to accommodate the different requirements for living and sleeping spaces, especially as many people still want heated towel rails in their bathrooms.’

Saffet Kalender, managing director of Aeon 
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Extended warranties

Look for systems that come with an extended warranty as standard. Wet systems consist of various components, and you may find different lengths of warranty are offered on each part — for example, 25 years on pipes, but perhaps two years on the manifolds. As a general rule, manifolds are simpler to replace than pipes, so a long warranty on the pipes themselves is highly desirable. With electric systems, extended warranties are usually in the order of one year for the thermostats, which are easily replaceable, and 10 years for the heating cables, which are not. Lifetime warranties are also available with some brands.

When looking at warranties, do ensure that the company backing it has some substance. A number of online companies have sprung up offering extended warranties on their systems, but if they are no longer in existence when the system fails then that warranty will be worthless.

David Green, director of Heat Mat 
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Engineered wood flooring works well with underfloor heating
Engineered wood copes better with changes in temperature than solid wood, meaning it’s a good match for underfloor heating. Kahrs Unity Cliff engineered wood flooring, £49.99 per m2, Carpetright

Other ‘invisible’ forms of heating

Skirting board heating
‘Wet or electric skirting heating systems are a great option,’ says Martin Wadsworth, managing director at Discrete Heat. ‘Wet systems can be used with heat pumps as well as conventional boilers due to their large surface area and the even distribution of heat around rooms. Direct electric versions are easier and simpler to install into properties with no existing gas or pipework, but are more expensive to run. However, their fast response times and even heat distribution does offset some of the additional costs when compared to other forms of electric heating.’

Installation of a skirting board heating (below) system in a typical two bedroom semi-detached house would cost upwards of between £3,600 to £6,000, although cheaper, DIY supply-only options are available; expect to pay upwards of £500 to £720 per room.

Wall panel heating
Variotherm modular wall and ceiling heating panels (above) are a solution for rooms where underfloor heating is not an option, whether in renovations or new builds. They are easily adaptable for walls, sloping ceilings and complex roof structures. Full systems start from £70 per sq metre, including the manifold, boards and controls, from UFH1.

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