Discover everything you need to know about underfloor heating
As the weather cools, nothing beats the luxury of warmth underfoot – especially first thing in the morning. Underfloor heating (UFH) is also energy efficient, convenient, frees up wall space and can add value to your home. As for installing it, the process isn’t as intrusive as you might think.
Read on for more information from which underfloor heating types are available to how to install underfloor heating.
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Why choose underfloor heating?
Ask any homeowner who has underfloor heating, and chances are they’ll say they’d never be without it! But why? Well one good reason is that, with underfloor heating installed, there’s no need for radiators. Aside from spoiling the clean lines of a room, radiators can take up valuable wall space. Remove them, and suddenly a gap appears for extra kitchen units, storage, a sofa or even a doorway.
Underfloor heating is also an extremely cost effective way to warm a room, so it will help you cut your fuel bills. Plus, unlike radiators, stoves or traditional solid-fuel fires, it provides the ultimate comfort levels by distributing heat evenly and gently. There are no cold spots and, as most of the heat is concentrated in the lower part of the room, very little heat is wasted.
If you’re planning on renovating your kitchen, there are even more reasons to choose underfloor heating. UFH runs on an independent thermostat, so if your cooker is generating a lot of heat, it’s possible to turn the heating off in the kitchen but keep it on across the rest of the house. As for cleaning, underfloor heating is a dream. Eliminating radiators means one less surface in the kitchen to attract grease and gather dust, and underfloor heating also results in less air movement. Less air movement equals less dust movement, making UFH more hygienic, especially ideal for allergy sufferers.
Know your types of underfloor heating – wet versus dry systems
There are two kinds of underfloor heating – electric or ‘dry’ systems and water-based or ‘wet’ systems .
Electric systems are more a ordable and less disruptive to install, but their running costs are higher, so they are best suited to smaller spaces such as tiled bathrooms, or spots that are awkward to get to.
Hot-water (or wet) systems
Wet systems are made up of pipes that are typically connected to your boiler, and use warm water from the central heating system. While a condensing boiler will offer the greatest potential savings on running costs, any boiler can be used with UFH, as long as it has a sufficient capacity.
The water is pumped through plastic pipes that are laid on to a sub floor, before the new final surface is installed. Most of the plastic water pipes installed in today’s systems are continuous, so there is no danger of leaks as there are no joints – and the system is generally considered to be maintenance-free.
By nature, they are more costly and disruptive to install (especially if a floor-level alteration is needed to accommodate the pipes). However, they are the most cost effective solution. Underfloor heating of this type also reduces water-heating costs as it uses water at a lower temperature than standard radiators (about 40°C to 65°C to give a floor temperature of between 23°C and 32°C).
If you’re looking to heat a large area, this is the best option.
Electric mat (or dry) systems
Dry UFH is available in the form of basic heating cables, sometimes loosely woven into mesh mats, flat or ribbon cables, or heating films. The mats or rolls are spread out, connected together and are then linked up to the thermostat and mains power supply. Your flooring is then laid on top.
There are three types of dry UFH available: Loose wire is suitable for stone or tile floors and ideal for irregular- shaped rooms with awkward corners or obstacles. Matting is good for stone or tile floors, too, and large or more regular-shaped rooms. A foil mat system is designed specifically for laminate flooring.
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In general, electric systems are cheaper to install, and cause less disruption to existing floor structure. They also allow the room to reach the required temperature faster than the wet varieties because they are direct heat sources. On the downside, they are more expensive to run than wet systems, which are more cost efficient.
Where to use underfloor heating
Underfloor heating is mostly used in ground-floor rooms but, in reality, there is a system to suit any type of floor construction. Wet systems are most easily installed where it’s possible to take up floors or where new floors are being constructed, so is likely to suit new extensions, conservatories and new open-plan kitchen-cum-living areas.
Electric underfloor heating is likely to be more suitable for existing rooms as the electrical mesh system is flatter than a wet system so there is less need for floor heights to be altered to accommodate it. There are even electrical mat systems available that can be used under rugs on existing hard floors. On balance, it’s easier to add electric systems to upper-floor rooms.
Can I lay underfloor heating with wooden flooring?
As a general rule, solid wood floors are not suitable for use with underfloor heating, unless specified by the manufacturer. Engineered boards, which are composed of at least three layers of wood laid with the grain of the centre layer running at right angles to the outer layers, are less prone to movement and most can be used with underfloor heating.
‘Underfloor heating and engineered wooden flooring can make excellent partners,’ says Peter Keane, director at The Natural Wood Flooring Company. ‘Robust and reliable, engineered wood can prove a far better choice than natural wood because it’s unlikely to alter when exposed to changes in temperature and humidity levels’
Any timber flooring recommended for use with UFH should have a top temperature restriction (usually 27°C) and an expansion gap needs to be left around the edges (this is easily hidden by a skirting board or trim). Always liaise with the flooring supplier and heating installer before making your purchase. Many suppliers will recommend a specific brand of electric UFH and it’s a good idea to listen to their advice.
What about other floor types?
Your type of flooring can help heat travel through – or diminish it. Thick carpet will lessen the benefits, but tiles, laminate and solid and engineered wood floors are good at conducting the heat (but check first if a wood floor has a recommended maximum temperature).
UFH can be used with almost all types of flooring, even carpet, providing that the carpet and underlay have a thermal resistance of less than 2.5 tog. Indications show that, for the majority of carpet styles, the thermal resistance will be less than 1 tog.
Stone, ceramic, slate and terracotta
As these flooring materials have become more fashionable, there has been an increase in the number of homes using UFH. Heat-up time depends on the thickness of the tiles. Thick flagstones will take longer to reach optimum temperature, but once this is reached there’s no difference in heat quality between thick or thinner floor surfaces.
Vinyls and laminates
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UFH can be used with high-quality vinyls and laminates. However, not all laminates or vinyls are compatible with UFH, so it’s a good idea to check with the flooring manufacturer or the heating installer before committing. Many suppliers have developed their own UFH systems, or have one or two that they recommend.
Underfloor heating – getting the timing right
It takes longer to heat a room with UFH than turning on radiators, but once the system is switched off the room stays warm for much longer. A couple of hours in the morning is usually enough to keep a room warm for most of the day, with a boost in the early evening. If you still have radiators in other rooms, it’s best to run your UFH on a separate heating zone with direct boiler control.
How much does it cost to install and run underfloor heating?
Installing a wet UFH system throughout a new build would cost around £5,000 all-in, but for an existing property, it depends on the size of the room and how much floor lifting is required. For just the system, a wet version will cost £20-£30 per sq m excluding fitting.
Either way, that’s significantly more expensive to fit than a dry UFH system. The good news, however, is that once installed, wet UFH can be 30 per cent more efficient than traditional radiators and far more economical to use. It’s also significantly cheaper to actually run than dry UFH.
An electric system makes economic sense if fitting it in one room. Prices for roll-out UFH mats start from around £75 per sq m, or a loose-fit kit from around £100 per sq m, plus insulation board and electrician’s charges. However, while electric UFH is cheaper to install than a wet system, it may also be anything up to 40 per cent more expensive to run.
For a wet system, use specialist companies, such as Nu-Heat or FloRad, which offer an all-in service.
How to install underfloor heating
1. Seek professional advice before you start
Don’t go ahead without professional advice to help you calculate the desired temperatures, the ceiling height, the potential heat loss and the type of flooring required. Carpet and natural wood are not the best insulators, whereas engineered wood, stone, marble and slate are ideal.
‘Begin by contacting at least two reputable, experienced suppliers,’ advises Adrian Troop, joint Managing Director at Nu-Heat. ‘The BEAMA trade association website has a list of members and can be a useful starting point. Discuss all of the installation and oorcoverings options with potential suppliers.’
2. Are you planning a renovation or a retrofit?
The best way to install wet underfloor heating is as part of a renovation or extension, and at an early stage of the the work. If this isn’t the case, you’ll either have to take up existing flooring and lay new – screed is best with the underfloor system laid on top – or add a floating floor to accommodate the piping. This raises the level of the floor, which in turn affects skirting boards and means doors will have to be rehung. One solution is to use very shallow piping, less than 20mm in diameter.
If you’re fitting retrospectively, low-profile and lightweight super-thin systems can be applied to sub-floor surfaces. Some designs are only 15mm deep, negating the need to alter skirting boards, door frames and stairs.
‘If your underfloor heating is going to be installed in multiple rooms, make sure that the system includes a detailed design that is tailored to your requirements and will take the fabric of your property into account,’ says Adrian. ‘And do try to ensure that your underfloor heating will effectively heat each room without the need for any supplementary heating.’
3. Take insulation into account
For your underfloor heating to be most cost- and energy-efficient, your property needs to be adequately insulated. To prevent heat loss, and to ensure that the heat is directed upwards, there needs to be room for insulation to be installed beneath the system. Bear in mind that if you live in a single-glazed property, you may still need to combine underfloor heating with radiators to create enough warmth.
4. Think about where the controls will go
With wet systems, make sure you have a space for the controls to be situated (a cupboard will do). Like a radiator, each room heated with UFH has its own valve. But they can all be sited in one spot, along with the timer controls. Also consider using systems that work with apps, such as Hive. This will enable you to control the heating via your smartphone.
5. Can I do it myself?
DIY kits are available from many manufacturers, but installing a wet UFH system is pretty labour intensive and complex. It’s therefore advisable that wet UFH should only be fitted by a professional. They’ll check that the boiler is powerful enough to support the system, and set up the timers and valve controls.
Electric dry systems are another matter. Provided you follow the instructions, it’s simple enough to fit a dry systems as a DIY product. However, you should secure the services of a qualified electrician to connect the cables or mats to the mains supply. Any domestic electric heating installation must be also signed off by an electrician, under the 2005 Part P Building Regulations.
6. Decide on an installer
Finally, think about who will do the installation for you. Do you have a local plumber who could fit the system? If not, your heating supplier should have a network of installers that they can refer you to.
Stay toasty people!