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Underfloor Heating Buying Guide

What are the benefits of underfloor heating?
Is electric underfloor heating better than water?
Which floor coverings work best with underfloor heating?
How do I choose the right system for my floor covering?
What type of system should I use?
What wattage should I choose?
What size underfloor heating kit do I need?
What insulation do I need beneath my underfloor heating system?
How do I choose an underfloor heating thermostat?
How do you install electric underfloor heating?
What else do I need to install my underfloor heating?
What’s the best underfloor heating system for bathrooms?
What are the benefits of underfloor heating?

Benefits

Comfort

In terms of comfort, underfloor heating is without parallel. It’s the only heating solution that warms the floor as well as the room, so you can say goodbye to those chilly mornings where you wince as you step onto chilly tiles. You’ll be surprised what a difference it makes when you’re not losing heat from your feet into cold floors. You’ll also find that your room is much more evenly heated than with radiator systems, because the heating system spreads across the entire room, rather than creating hot spots around individual radiators. The steady rise of radiated heat is much more even and comfortable than the restless movement of convection heat from radiators. Underfloor heating systems are also much quieter than radiator systems. Electric underfloor heating systems are usually entirely silent, depending on the quality of your installation.

Efficiency

Underfloor heating systems are particularly efficient because they heat entirely by radiation.

Most heating systems deliver the majority of their heat through convection – radiators and central heating systems included. Cold air circulating through the room heats up as it passes through the radiator. This hot air rises to the top of the room until it cools, sinks, and passes through the radiator again. This cycle keeps the air in the room warm so that it can transfer its heat to the room’s occupants. This system is fairly effective but not very efficient: plenty of heat is lost as it transfers from radiator to air to room occupant, and warm air can easily escape through draughts and opened doors. Because hot air rises, the ceiling will always warm up before the lower areas of the room – not very useful!

Radiation, meanwhile, cuts out the middleman by heating people directly. Underfloor heating systems warm up the floor, which radiates heat upwards, warming the room from the ground upwards. Not only is this more efficient – you’ll also notice the heat much faster because it heats living levels before heating the ceiling, unlike radiators.

Underfloor heating systems are also much more controllable than central heating systems, which allows you to save power and money by only heating the rooms which will be in use. Each room in an underfloor heating system has its own thermostat, unlike a central heating system which is limited by a single, central thermostat, so you can program your heating room by room.

Home Design

Underfloor heating gives you the ultimate freedom in your home interior design. With your heating system neatly hidden away under the floor, you don’t need to worry about finding radiators that match your design scheme. Underfloor heating frees up your wall space entirely, which is particularly useful in rooms with lots of furniture such as kitchens, bathrooms and libraries.

Health & Safety

Another benefit to having your heating system hidden under the floor is that it cannot gather dust. Central heating radiators are often guilty of exacerbating allergies as the dust which collects inside them is transported around the room on the heated air. Underfloor heating does not do this, making it the ideal heating system for allergy suffers.

There are also safety benefits to having a concealed heating system that doesn’t require hot metal boxes. Underfloor heating is popular with families who have young children because it removes the risk of injury from falling against or running into central heating radiators. For this reason, underfloor heating is also a popular choice in homes for elderly or disabled people.

No Maintenance

As long as your underfloor heating system is properly installed, it shouldn’t require any maintenance. There are no moving parts in underfloor heating systems, so there’s very little to go wrong! You can also forego the fiddly cleaning operations required to keeping radiators and electric heaters free from dust.
Is electric underfloor heating better than water?

Electric vs Water

Electric and water underfloor heating systems are quite different, so it’s usually best to decide which one you want to go for before you start shopping. Each has its benefits and drawbacks. As a general rule, water underfloor heating is the most popular choice for new builds, while electric underfloor heating is the cheaper and easier option for retro-fitting in existing houses.

Electric Underfloor Heating

Electric underfloor heating systems are comprised of a roll of cable spaced out beneath the floor covering. As the cables heat up, the floor radiates heat up into the room.

Advantages

Electric underfloor heating is usually cheaper to install than wet underfloor heating. It can be fitted directly on top of your existing flooring, with nothing more than a layer of insulation beneath to capture the heat. Many of the initial stages of installation can even be tackled DIY, although you’ll always need a qualified electrician to hardwire the system into the mains and wire your thermostat. Electric underfloor heating cable can be as little as 2mm thick, so your system will only raise floor heights to a minimal degree. For both these reasons, electric underfloor heating is the most popular choice for retro-fitting projects.

Electric systems usually heat up faster than water systems. They are maintenance free and do not require you to balance the hot water supply from your boiler. Electronic thermostats offer precision control of your floor and room temperature, helping you to manage your system more efficiently. If you are looking at heating an eco-home, electric underfloor heating can be a suitable option powered by electricity generated from wind turbines or solar panels.

Disadvantages

Electric underfloor heating has many advantages, but does share some disadvantages with other types of electric heating. Electricity is usually more expensive than gas, so running costs of electric underfloor heating tend to be higher than water underfloor heating. These costs may or may not be balanced out by the relative cheapness of installing electric underfloor heating. Electricity generally works out cheaper overall in retro-fitting projects, or in well-insulated locations that only require low levels of heat to maintain comfort temperatures.

Another drawback to electric underfloor heating is that it will not work if there is a power cut.

Water Underfloor Heating

Water underfloor heating systems are comprised of a system of pipes. As hot water flows through the pipes, the floor heats up and radiates heat into the room.

Advantages

Like central heating, water underfloor heating systems are powered by your boiler. This means you can take advantage of the cheaper cost of oil or gas over electricity; water underfloor heating systems are usually cheaper to run than electric underfloor heating systems. You’ll also avoid the risk of losing your heating because of a power cut.

Water underfloor heating systems can be effectively paired with a ground source or air source heat pump to provide an eco-friendly heating solution.

Disadvantages

Water underfloor heating systems are more expensive to install than electric systems. Ideally, the pipes will be recessed into the floor, either between the joists if you have a wooden sub-floor, or set in screed if you have a concrete sub-floor. This is a time-consuming and disruptive process in an existing house because you will need to refit your subfloor. Retro-fitting systems are available, however, because heating pipes are thicker than heating cables, these systems will raise your floor level by a considerable amount. It is usually only economical and practical to fit water underfloor heating in a new build, where you can take advantage of a “clean slate” for installation. In new build projects, the cheaper running costs of water underfloor heating will outweigh the initial cost of installation.

Another disadvantage to the more “integrated” installation of water underfloor heating is that the system is difficult to access in the event of a problem. Water underfloor systems also heat up slower than electric systems, and are difficult to install in upstairs rooms. You will also need to factor into your budget the cost of having your boiler maintained and serviced every year.

Which floor coverings work best with underfloor heating?

Floor Coverings

Underfloor heating systems work by conduction and radiation. Heat travels by conduction from the heating cables to the floor covering, which heats up and radiates heat out into the room. This means that the best floor coverings for efficient heating are those which are good conductors of heat.

Tiles, Stone & Concrete

Tiled, stone and concrete floor coverings are the best choice for efficient underfloor heating. Stone floors are excellent at both conducting and retaining heat, which means they heat up fast and maintain temperatures efficiently. Stone floors can be heated to 29 °C or more – higher than any other floor covering. This means they can be used with 200w/m² systems, making them uniquely suitable for areas of high heat loss such as conservatories.

To get the most out of a tile, stone or concrete floor, we recommend choosing floor coverings with a maximum thickness of 20mm. Thicker stone floor coverings will not reduce the heat output but they will take longer to heat up. Popular choices include ceramic tiles, stone tiles, polished screed, slate, flagstone and marble.

Vinyl

Vinyl is a surprisingly good conductor of heat, offering a cheap alternative to stone tiled flooring. Vinyl tiles are typically thin, which makes them both good conductors and poor retainers of heat. They will heat up fast but cool down quickly. Vinyl floors are subject to a heat restriction of 27 °C. This means they should only be used with systems of 150w/m² or less, unless the temperature is limited via the thermostat.

Many types of vinyl, rubber and linoleum floor coverings are suitable for use with underfloor heating, however you should always check with the manufacturer before fitting.

Wood & Laminates

Wood and laminate flooring can provide a handsome and effective floor covering for your underfloor heating. However, there are many different types of wood floor covering available, not all of which will be good conductors of heat. Wooden floor coverings should not be heated above 27 °C, so should only be used with systems of 150w/m2 or less, unless the temperature is limited via the thermostat.

The most effective wooden floor coverings are those which are thinnest and most dense. Thin wooden floors will heat up faster than thicker wooden floors, whilst dense wooden floors will conduct heat more effectively than porous wooden floors which effectively insulate the heat with pockets of trapped air. As a general rule, you should look for wooden floor coverings that are no more than 18mm thick. Engineered timber and kiln dried floors typically make the best pairing with underfloor heating because they adapt well to changes in temperature. Solid wood floors are usually unsuitable because they are very sensitive to changes in temperature and humidity; they are also more likely to act as an insulator, because they are typically thick and not very dense.

Such is the range and diversity of wooden floor coverings available that you should always defer to the manufacturer’s guidelines regarding installation instructions and suitability for use with underfloor heating.

Carpet

Contrary to popular belief, carpet is suitable for use with underfloor heating. Carpet is a poor conductor of heat, so does not make the best choice if you want to optimise the efficiency of your underfloor heating. However, it does provide a luxurious combination that may be exactly what you’re after – giving you soft, warm, exceptionally comfortable floors.

Carpeted floors should not be heated beyond 27 °C, so should only be used with systems of 150w/m2 or less, unless fitted with a temperature-limiting thermostat. It is also important to ensure that the carpet, underlay and any overlays required for your installation do not exceed a combined tog rating of 2.5 tog. A combined tog rating of more than 2.5 tog will insulate your system to the extent that it will not be able to provide a sufficient heat output.

Always check with the manufacturer before purchasing a carpet for use with your underfloor heating system.

How do I choose the right system for my floor covering?

Systems & Floor Coverings

If you’ve already chosen your floor covering and are looking for an underfloor heating system to match, see below for advice on the best system to use.

Tile & Stone Floors

Tiled, stone and concrete floors should be paired with either a loose cable or sticky mat underfloor heating system.

Foil mat heating systems should not be used with these floor types because tile adhesive, screed and concrete will not adhere to the foil matting.

Wood, Laminate, Carpet & Vinyl Floors

These floor types are most popularly used with foil mat systems. This is because foil mats are the easiest underfloor heating system to install. They do not require any form of adhesive: the floor covering simply lies over the top of the foil mat. Wood and laminate floors lie directly on top of the mat, whilst vinyl and carpet floors require a thin layer of MDF in between to protect the wire from damage.

However, it is possible to use wood, laminate, carpet and vinyl floor coverings with a sticky mat or loose cable system. The main reason for doing this is to futureproof your system. Tile and stone floors cannot be used with foil mat systems, so if you want the option of a tiled floor in future, you should choose a loose wire or sticky mat system. You will need to use a layer of self-levelling compound at least 10mm deep before fitting a wood, laminate, carpet or vinyl floor on a loose wire or sticky mat system.

What type of system should I use?

Underfloor Heating Systems

All types of electric underfloor heating are made up of wires which fit beneath the floor. As the wires warm up, the floor is warmed and heat radiates out into the room. Heat naturally rises, helping your underfloor heating system warm the room from the floor to the ceiling, delivering heat where you need it first, rather than last.

There are four main types of underfloor heating: loose cables, sticky mats, foil mats and in screed cables.

Loose cables, sticky mats and foil mats are all retro-fitting options suitable for installing above existing flooring. We sell a wide range of loose cables, sticky mats and foil mats suitable for a variety of floor coverings.

In screed cables are designed for new build properties. These cables are set in concrete and installed in the building’s sub floor. We do not currently stock in screed cables.

Your choice of product will depend on a range of factors including the size and shape of your room, the type of floor covering used, and whether or not you are retro-fitting.

Loose Cables

Loose cable or loose wire systems are sold as a reel of heating wire which can be spaced across the floor to create the required level of heating. The closer you space the wires, the higher the level of heat your system can raise – and the faster your rooms will heat up.

Loose wire kits offer the most flexibility of all the underfloor heating systems. The cables are easy to fit around small spaces and awkward items of furniture such as basins and toilets. This makes them particularly popular in small rooms and bathrooms. Loose wire kits are easy to retro-fit over existing floors, and can be used beneath all major floor coverings – including tiled, stone, vinyl, carpet, wood and laminate floors.

Like other retro-fitting options, a loose wire kit will raise your floor height somewhat, but this will only be a matter of millimetres. The main disadvantage of loose wire systems is that they can be time consuming to install. The cables must be spaced out and taped down by hand, which takes longer than mat systems which simply unroll over the floor.

Sticky Mats

Sticky mats are rolls of self-adhesive mesh with underfloor heating cables pre-spaced along their length. Mats with cables more closely spaced will be able to give off a higher level of heat and will heat up faster than mats with cables further apart.

Sticky mats can be installed much faster than loose wire systems. All you have to do is unroll the mats over the floor, cutting the netting when you reach the wall so you can flip the mat and continue unrolling in the opposite direction. You must never cut the cables. Sticky mats are suitable for use with all major floor covering types, including tiled, stone, wood, laminate, carpet and vinyl floors.

Like all retro-fitting options, sticky mats will raise your floor height by a few millimetres. Whilst sticky mats are faster and easier to install in large, square rooms, you may find the flexibility offered by loose wire kits more practical when installing underfloor heating in a small or awkwardly shaped room.

Foil Mats

Foil mats are designed for use with wood, laminate, carpet and vinyl floors. They comprise a length of cable pre-spaced and fitted inside a foil mat.

Foil mats are the easiest underfloor heating system to install. Like sticky mats, they simply unroll over the floor. Unlike sticky mats, however, they do not require any adhesive layers; wood and laminate floors can be laid directly over the foil, whilst carpet and vinyl floors need only an intermediary layer of MDF overlay to protect the heating cables. Foil mats are the best system to choose if you want a fast and easy installation that’s possible to undertake as a DIY project. However, you will still need the help of a qualified electrician to connect your system to the mains and wire your thermostat.

The main drawback to foil mat systems is that they cannot be used with tile or stone floor coverings. This is because adhesive layers such as tile adhesive, self-levelling compound and screed will not adhere to the foil surface. We don’t recommend choosing a foil mat system if you think you may want a tile or stone floor covering in the future. Loose wire and sticky mat systems are the futureproof choice; they can be used with carpet, vinyl, wood and laminate floor coverings as long as a 10mm layer of self-levelling compound is used on top of the cables.

Like all retro-fitting underfloor heating systems, foil mats will raise your floor height by a matter of millimetres. It’s also worth noting that the MDF layer required when fitting carpet or vinyl floor coverings over a foil mat is not waterproof. For this reason, we do not recommend foil mat underfloor heating in a carpeted or vinyl-floored bathroom.

In Screed Cables

In screed cables are thick underfloor heating cables which are designed to be set within screed in the sub-floor of new build houses.

The main advantage of in screed cables is that they do not raise overall floor heights. They can also be used with all major types of floor covering, including tiled, stone, carpet, vinyl, wood and laminate floors.

However, the installation process for in screed cables is tricky and time consuming. It is best left to the professionals, and is usually only a practical option in new build properties.

What wattage should I choose?

Wattage

Wattage measures the heat output of your underfloor heating, determining how fast your system will heat up, and the maximum temperature it can reach. The wattage of any underfloor heating system depends on the spacing of the cables. The more closely spaced the cables, the more power is available to heat your room, allowing the room to reach a higher temperature and heat up faster.

Unlike other heating systems, which are measured in Watts, underfloor heating heat output is measured in Watts per metre squared (w/m²). This is because the density of cables determines the heat level, rather than the overall wattage.

For instance, a 2000W cable evenly spaced in a 10m² room will provide a high level of heat. The same cable evenly spaced in a 20m² room will provide a much lower level of heat. The first system has a high 200w/m² wattage; the second system has a low 100w/m² wattage. Comparing heating systems by their w/m² is the best way to ensure you’re choosing a kit which offers the level of heat you need.

Underfloor heating kits are available with a range of wattages, usually ranging from 100w/m² to 200w/m². Sticky mat and foil mat heating systems come with the cables pre-spaced to provide a certain wattage, whilst loose wire kits must be spaced by hand to make up the required wattage. Of course, a loose wire heating kit gives you the flexibility to create whatever wattage you like, depending on how you space the cables, but you should always defer to the manufacturer’s guidance before committing to your heating plan. It is not normally safe to place heating cables closer together than 5cm – the spacing required for a 200w/m² heat output. We sell our loose wire kits by wattage, with kits available for different room areas, to make it easier for you to choose the right amount of cable for your project.

Your choice of wattage depends on three main factors: the level of heating you require, the level of heat loss in your room, and how fast you want your system to heat up.

Room heating or floor heating?

The first question to ask is whether you want underfloor heating as a primary heating source, or just to keep your floors warm?

If you just want to keep your floor warm, a low wattage system will be adequate. Look out for heating mats and cable kits with wattages from 100w/m² to 130w/m².

If you want to use underfloor heating as your primary room heating source, you will need to choose a system with a wattage sufficient to warm the entire space. To do this, you will need to consider the rate of heat loss from the room.

Standard vs high heat loss

Rooms in exposed locations with poor insulation, single glazed windows and high ceilings will inevitably have a higher rate of heat loss than well insulated rooms with double glazed windows and standard ceiling heights. Rooms with a high rate of heat loss will require more power to keep them at a comfortable temperature than well insulated rooms.

As a general rule, a system of 140w/m² to 150w/m² should be adequate for a room with a standard rate of heat loss.

Rooms with a high rate of heat loss will require a higher wattage system to ensure temperatures can be maintained. Wattage kits of 190w/m² to 200w/m² are recommended for rooms which are poorly insulated – such as period properties, conservatories and garage conversions – and rooms which have a high volume to heat, such as high-ceilinged rooms, hallways and multi-storey spaces.

It may also be advantageous to use a 200w/m² system in rooms such as kitchens which have a lot of floor space taken up by fixed furnishings. This is because your heating area will be much smaller than the overall area of the room you are trying to heat. If more than 20% of your floor surface area is taken up by fixed furniture, you should be considering a 200w/m² heating system.

Heat up times

There are other benefits of choosing a higher wattage underfloor heating kit. The higher your wattage, the faster your system will heat up. This remains true even if you only require a low level of heat from your underfloor heating. All underfloor heating systems are regulated by a thermostat which prevents room and floor temperatures rising over a set level, so it is quite possible to have a high wattage system that only creates a low level of heat; the system will heat up fast, but then spend most of its time switched off, only clicking on again when the heat needs topping up.

It goes without saying that high wattage systems are more expensive than lower wattages, because you will be using more cable to heat the same sized space.

Wattage & floor covering

Not all floor coverings can be raised to the temperatures required to heat poorly insulated spaces. When you choose the wattage of your underfloor heating, you should make sure it is compatible with your intended floor covering.

Only tile and stone floor coverings can be heated to the level required in areas of high heat loss. For this reason, we always recommend choosing a tile or stone floor finish for conservatories, garage conversions, and other high wattage environments that need a 200w/m² kit for comfortable heating.

Most wood, laminate, carpet and vinyl floor coverings are subject to a 27 °C temperature limit to prevent damage. This can be achieved with a 140w/m² to 150w/m² kit and is sufficient for comfort heating in rooms with standard levels of insulation. However, this may not be hot enough if your room has a high rate of heat loss. You can still use a high wattage system with these floor coverings if you want to take advantage of their faster heat up times, but you must use the thermostat to restrict the floor temperature, which means the room will not get warmer overall.

We always recommend checking the temperature limit of your floor covering with the manufacturer before choosing an underfloor heating system.

What size underfloor heating kit do I need?

Sizes

Calculating your floor area

All of our underfloor heating packages are sold by room area, with each kit designed to cover a certain size floor area with a certain heat output. Once you’ve worked out the wattage you need from your underfloor heating, all you have to do is select a product with the appropriate wattage and choose a kit, or combination of kits, that will cover the area to be heated.

Calculating your heated floor area is simply a matter of subtracting the area of any fixed or permanent room furnishings from your total room area. We then recommend taking a further 10% off your total, to ensure you do not purchase a heating system which is too large. We’ve made this even easier with our room area calculator.

It is very important that you do not order an underfloor heating kit which is too large, because the wires cannot be cut.

If you prefer, you can send the details of your installation to our sales team who will happily send you a free quote.

Which furnishings should you exclude from your heating plan?

When you work out your heating area, it’s important to exclude any permanent furnishings or fixtures. This includes features which you cannot heat under – such as chimney breasts, columns, staircases, baths, sinks and toilets – and features which you should not heat under – namely, any permanent piece of furniture with a solid base.

Permanent furnishings with a solid base will obstruct the heat output of your underfloor heating. This wastes energy, does nothing to warm your room and can also damage the cables over time.

Examples of permanent fixtures and solid furnishings which you should plan around include kitchen units, washing machines, fridges, shelving units, cabinets and sofas. You may also wish to plan around smaller, semi-permanent items of furniture which nevertheless cover a significant amount of floor space: dog beds, washing baskets and storage boxes are good examples. We do not recommend using rugs in rooms with underfloor heating.

You can, however, fit underfloor heating beneath larger items of furniture that have plenty of clearance from the floor. Tables, chairs and raised desks can all be positioned over underfloor heating systems because they allow plenty of room for the heat to radiate from the floor and circulate around the rest of the room.

If more than 20% of your floor space is excluded from your heating plan, you may wish to consider a 200w/m² heating system to ensure your system can keep the entire room at a comfortable temperature. 200w/m² systems will only be effective if used with tiled or stone floor coverings.

Choosing the right size product

Once you’ve calculated the size of your heated area, and chosen the wattage at which you want to heat, choosing the right size product for your room is an easy task.

We sell our underfloor heating cables and mats in pre-assembled packages for set floor areas. Simply click on the product of your choice and choose your heated area from the dropdown menu.

If we do not stock a package just right for your room size, you may need to combine heaters to make up your floor area. For instance, to heat a 9m² room with our Warmup sticky mats, you will need to use a 4m² and 5m² sticky mat system. Combining floor area packages in this fashion is fairly intuitive. However, for clarity, you will find a chart showing recommended combinations for selected floor areas on every product page.

Remember, it’s always wise to choose a heating system which is slightly smaller than your heated area, rather than larger. Cables can be rearranged to fit a larger area, but they cannot be cut to fit a smaller area. If your area falls between two available sizes, always go for the smaller size – do not be tempted to round up!

What insulation do I need beneath my underfloor heating system?

Insulation

Why does underfloor heating need insulation?

All underfloor heating systems should be installed with a layer of insulation between the heating system and the substrate. This prevents heat escaping down into the ground, forcing heat to conduct upwards into the room. This reduces heat loss considerably, making your system much more efficient. Your underfloor heating system will warm your rooms up to ten times faster when backed by a good level of suitable insulation.

Even if you are retro-fitting your underfloor heating over an existing, already insulated floor level, it is still important to fit your heating with a new layer of insulation. This is because your old floor covering will act as a conductor, allowing heat to escape downwards until it reaches your in-situ insulation. With a new layer of insulation in place, all this heat will be directed upwards, into the room.

Insulation can also serve a number of other purposes, depending on what type of underfloor system you’re planning to install. Soft insulation boards provide cushioning to foil mat systems, whilst cement coated insulation boards provide support to tiled floor coverings. You can also use suitable insulation boards for waterproofing and soundproofing.

Choosing the right type of insulation for your heating project

Insulation boards may look identical, but in actual fact there are many different types. Choosing the right type of insulation is essential to ensure your heating system is securely fitted and has all the support it needs.

To make this easier for you, we’ve specified on every product page what type of insulation board you need, depending on your sub-floor. We’ve even added calculators to show you how much you’ll need, so you can add the boards to your basket there and then. But if you’re interested in why you need certain boards for certain projects – read on!

Insulation boards vary in several ways, including: density, rigidity, solidity, thickness, the level of sound-proofing they offer, whether or not they are waterproof, and whether or not they have a cement coating.

Coated vs Uncoated

The most important thing to check when choosing your boards is whether the boards need to be coated and whether they need to be dense.

Coated boards are necessary whenever a firm, level surface is required – for example when under-tile systems are used on top of a timber substrate. Conversely, uncoated boards may be required if your heating system needs cushioning to prevent damage – for example when a foil heater is used directly under wooden flooring.

Uncoated boards vary in their density. Dense boards are better insulators and can be stuck down with a suitable adhesive. They are the best choice for installations that don’t require a coated board but do require boards that can be fixed to the substrate – for example, under-tile systems over a concrete substrate. Dense boards can also be used without adhesive with foil heating mats if you want to take advantage of their superior insulative properties. Less dense boards are cheaper, but are less insulative and too spongy to be used with adhesive. This means they are only suitable for use under foil heating mats.

Confused? You can check what sort of boards are needed for your heating system using the table below.

Heating System Sub Floor Insulation Boards Required
Loose Cables or Sticky Wire Timber Coated boards are required to give a firm, level surface for the levelling compound or tiles.
Concrete Uncoated boards can be used because the system already has a firm substrate. You will need to use dense boards so that they can be fixed to the substrate using a flexible adhesive.
Foil Mat Any Uncoated boards should be used to provide cushioning to the heating elements in the foil mat. Non-dense boards will be sufficient; however, you may wish to use dense boards if you want a thicker layer of insulation.
Thickness

You will find that some boards are available in different thicknesses. Choosing the thickness of your insulation is always a trade-off between making your system more efficient and minimising the degree to which your floor level is raised. The thicker your insulation, the faster your system will heat up and the more efficient it will be. As a general rule, all underfloor heating installations should have a minimum of 5mm insulation between the sub-floor and the heating system.

R Value

An easy way to compare the level of insulation offered by competing boards is to check the boards’ R Values. R Values measure the level of thermal resistance offered by the boards. The higher the number, the higher the quality of insulation.

How much insulation do you need?

You can use our board calculators to work out how many boards you will need to cover your floor area.

Insulation boards are sold in packs by floor area coverage, so, in theory, it is quite easy to work out exactly how many boards you will need to cover a certain size area. However, in practice, you will find that you need several more boards than the total required to make up your surface area. This is because boards will have to be cut and rearranged to suit the exact shape of your room and fit around any awkward fixtures.

The board calculator takes this into account, ensuring the number of boards you order will be sufficient to insulate your entire room – no matter how awkward the shape.

How do I choose an underfloor heating thermostat?

Thermostat

Why do underfloor heating systems need a thermostat?

It is essential that all underfloor heating systems are installed with a thermostat.

The job of the thermostat is to measure and maintain temperatures. Underfloor heating thermostats are unique in that they measure the floor temperature as well as the room temperature. This allows you to set a maximum temperature for your floor. This is essential for safety, ensuring you never overheat your floors and risk damage to the system. This also allows you to lay temperature-restricted floor coverings such as wood, carpet and linoleum, safe in the knowledge that your heating system will not exceed the standard limit of 27 °C.

The thermostat is your main point of control over your underfloor heating system, so it’s important you choose a model which offers the level of control you require to run your system efficiently and conveniently.

How many heating systems can one thermostat control?

You will usually only need one thermostat to control an entire room with underfloor heating. Large rooms and multi-room set-ups may require an additional thermostat.

Most thermostats are limited to two input cables and a maximum load of 16 Amps. In standard UK 230V systems, this equates to a limit of just over 3600W.

You can check the total wattage of your chosen underfloor heating system by looking in the product specification. However, as a general rule, a 16 Amp thermostat will be sufficient for the following room areas, depending on what wattage system you are using:

Wattage Maximum room area for one thermostat
100w/m2 36m2
150w/m2 24m2
200w/m2 18m2

If your underfloor heating system is made up of more than two separate heating mats or cables, your electrician may need to use a junction box to wire all the cables into the thermostat.

If your underfloor heating system exceeds the thermostat’s maximum load, it is possible for your electrician to use a contactor to switch the load. However, you should consider at this point whether it would be more advantageous to install a second thermostat. Large rooms and multi-room setups may have localised hot and cold spots, so a single thermostat may no longer give a representative reading for the entire space.

Where should the thermostat be installed?

Underfloor heating thermostats need to be connected to the mains by a qualified electrician. However, it is possible to perform the initial stages of installation DIY, including fitting the floor sensor as you lay your heating mats or cables. Check installation manuals and videos for a step-by-step guide.

We recommend seeking the advice of your electrician before choosing a location for your thermostat. The most sensible location for your thermostat will depend on the layout of your existing wiring, although it should be possible for your electrician to connect your thermostat to the mains from any position in the room.

Pre-existing wall mounted controllers will give a good indication of the best place to fit your thermostat. Most thermostats use the same basic wiring, so replacing an obsolete wall mounted controller with your underfloor heating thermostat would be a quick and easy job for any electrician.

If you are installing underfloor heating in a bathroom or wet room, the thermostat should be mounted in the next dry room – usually the hallway.

What’s the best kind of thermostat to use with underfloor heating?

There are a huge variety of thermostats available to use with underfloor heating, so it’s important you take the time to choose the best model for your home and lifestyle. We don’t include thermostats in our heating packs for this reason – you can pick the thermostat of your choice from the drop-down list when you make your order.

Here are some of the features to look out for when making your choice:

Manual or Digital

Manual thermostats offer rudimentary heating control with a traditional-style dial to adjust the temperature. Manual thermostats are easy to use but give you limited control over your heating. Most manual controllers give you basic on/off on-demand control and do not allow you to program your heating.

Digital thermostats are more accurate than manual thermostats and offer a greater degree of control. They typically sport more modern designs, with LCD or touchscreen displays. Most digital thermostats allow you to program your heating, and may well offer a raft of additional smart features.

It’s true to say that not all digital thermostats are equally easy to use. Older digital thermostats sometimes suffer from unintuitive interfaces which are difficult to use without consulting the manual. However, the most up-to-date digital thermostats have been carefully designed to optimise ease-of-use: employing sliders, touchscreens, Wi-Fi control and everyday language to make programming as intuitive as possible. A good digital thermostat will be as easy to use as a manual thermostat.

Programming

Programming your underfloor heating is an easy way to reduce your energy usage without compromising your comfort. When you program your heating, it will follow your personalised schedule automatically, switching on and off and changing temperature according to your needs. Your house will be warm when you wake up in the morning and get in from work, without wasting energy heating overnight, or when the house is empty.

The level of programming offered will vary between models. The most sophisticated thermostats will offer a range of pre-set programs as well as several customisable programs. They will allow you to set a different heating mode for every half-hour interval of every day of the week, and you will be able to choose from a range of customisable heating modes, such as comfort, economy and anti-freeze.

Thermostats which do not offer programming will work on a simple off/on, on-demand basis. This may be suitable for rooms you use on an occasional basis, such as workshops or conservatories, but is not recommended for your primary living spaces.

Wi-Fi Control

Thermostats with Wi-Fi control allow you to control your underfloor heating from anywhere in the world, provided you can connect to the internet. This is a very convenient feature which allows you to make adjustments to your heating while you’re at work, away on holiday, on public transport, or, indeed, sat comfortably on the sofa unwilling to get up and walk to the thermostat!

Wi-Fi controllable thermostats wire into the mains and connect to your underfloor heating in the same way as a regular thermostat. The thermostat will then connect to your Wi-Fi network in the same way as a phone or laptop. You will be able to control the thermostat by downloading the manufacturer’s app onto your device or creating an account on the manufacturer’s website.

Note that although Wi-Fi controllable thermostats are commonly referred to as “wireless”, they are only wireless in the way they communicate with mobile devices and laptops. They must be fully wired into both the mains and your underfloor heating system.

Design

Your thermostat needn’t be an eyesore. We sell thermostats in a wide range of colours with something to suit most interior design schemes. Our most sophisticated touchscreen thermostats come with customisable displays that allow you to change the colour scheme or even upload a personal photo as your backdrop, so there are plenty of ways to make sure your thermostat fits into your interior design.

Smart Features

These days, heating thermostats are more than simple temperature limiters. Today, underfloor heating thermostats are available with a raft of intelligent features designed to do everything from measuring your energy usage to checking the weather. Here are some of the best to look out for:

Energy Monitor

Thermostats with an energy monitor will record your energy usage, calculate running costs and generate graphs which show you how and when you use energy.

Learning Mode

Thermostats with learning mode work continuously to optimise your heating, adjusting heat output and programming to ensure comfortable heating is always provided as efficiently as possible. This can work on both a long term and a short term basis.

In the short term, the thermostat will adjust its heat output to compensate for changes in the immediate environment. These adjustments can range from switching off the heating when an open window is sensed, to programming the heating to switch on earlier when colder weather is forecast.

In the long term, your thermostat will learn how you like to use your heating and will adjust your schedule to find the most efficient way of warming the room to your preferences.

Tariff Switching

Tariff switching thermostats monitor your energy usage and keep a constant eye on the energy market to make sure you’re on the best value tariff. The thermostat will notify you if it finds a more competitive tariff – or you can set it to switch automatically.

Energy Saving Advice

The thermostat will analyse your energy usage and generate energy saving tips and advice specially tailored to your habits.

Additional Apps

You needn’t limit your thermostat to just controlling your heating. Why not choose a thermostat with additional apps and make it the central information hub for your home? Our smartest thermostats give you scope to download a wide range of handy, non-heating-related apps onto your thermostat. These might include weather forecasting, an outdoor temperature display, and even traffic reports tailored to your morning commute.

How do you install electric underfloor heating?

Installation

Is electric underfloor heating suitable for DIY installation?

Yes – almost the entire process of installing electric underfloor heating can be completed DIY, if you are so inclined. Preparing the sub-floor, fitting insulation, laying the heating mats or cable and installing the floor covering are all tasks which can be undertaken by a non-professional, depending on your level of DIY confidence and experience. The only part of the installation which must be completed by a professional electrician is the final step of connecting your heating system and thermostat to the mains.

Fitting your heating mats or cables is the easiest part of the installation process. If you are using mats, all you have to do is unroll the mats over the floor, cutting the mesh or foil and turning the mat whenever you need to go around a corner. If you are using loose cables, the process is more time consuming but not difficult. You will need to lay the cables out with the spacing prescribed for the wattage you want to achieve, taping the cables down as you go. This process requires more patience than skill, and is entirely suitable for home developers with the most basic levels of DIY experience.

What is required above and below your heating mats or cables will depend on three main factors: the sub-floor onto which the heating system will be installed, the insulation you need between the substrate and the heating system, and the floor covering you want to use on top.

Foil mat heaters are the easiest system to install DIY because they never require any adhesive layers: the floor covering simply lies on top of the foil, with an intermediary layer of MDF if you’re fitting a carpet or vinyl floor. Sticky mat and loose wire systems require a little more care, because you will need to work with either tile adhesive or levelling compound.

Some floor coverings may be more difficult to install, so, depending on your level of DIY experience and the advice of the floor covering manufacturer, you may prefer to have this top layer fitted by a professional.
Typically, you should be able to complete about 90% of the installation process DIY.

How do you install electric underfloor heating?

It’s very important you follow the instructions above to ensure that your underfloor heating is correctly installed. Unsuitable installation risks damage to both your heating system and your floor covering.

The installation build-up above and below your heating system will vary depending on your sub-floor, your floor covering, and the type of heating system you are using. Full installation instructions can be found in our product manuals and installation videos – however, to help you compare your options, we’ve summarised the main installation configurations below.

Sticky Mats & Loose Wire Kits

Sub Floor

If you’re installing a sticky mat or loose wire system on a wooden floor, you will need to use cement coated boards to provide a firm base for your tiles or any layers of self-levelling compound. Cement coated boards should be fixed to the floor with screws and washers.

If you’re installing a sticky mat or loose wire system on a concrete floor, you can use dense uncoated boards because your system already has a firm base. The boards should be bonded to the substrate with a layer of flexible tile adhesive.

Floor Covering

If you’re installing tiles or stone flagging over your sticky mat or loose wire system, you can apply tile adhesive straight over the heating system and fit your tiles above. Some installers prefer to lay an intermediary layer of self-levelling compound before fitting tiles. This can make laying the floor covering easier because it gives you a flat surface to work with.

If you want to use any other floor covering with your sticky mat or loose wire heating system, you will first need to lay a 10mm layer of levelling compound over the cables. This protects the cables from either the grinding pressure of wood and laminate floors, or the risk of penetration through soft floor coverings such as carpet or vinyl. Please be aware if fitting carpet that the combined tog rating of the carpet and underlay should not exceed 2.5 tog.

Foil Mats

All foil mats require a soft layer of uncoated insulation between the substrate and the mat. This cushions the cables in the mat and offsets the pressure from the floor covering, preventing damage. Foil mat insulation is available as boards or as a roll, and does not need to be adhered to the substrate; it can simply be lain beneath the heating mat.

Floor Covering

Laminate and wood floor coverings can simply be lain over the foil mat.

Carpet and vinyl floor coverings will need an additional layer of MDF dual overlay on top of the foil to protect the heating cables from damage. The MDF layer does not need to be fixed down – it can simply be lain over the foil mat. Please note that if fitting a carpet, the combined tog rating of the carpet and underlay should not exceed 2.5 tog.

Tile and stone floor coverings are not suitable for use with foil mats.

What else do I need to install my underfloor heating?

Adhesives, Levelling Compounds & Overlays

Once you’ve purchased your heating system, thermostat and insulation boards, you will be almost ready to start installation. However, depending on the required build-up of your underfloor heating, you may need to equip yourself with one or more of the following.

Tile Adhesive

Tile adhesive is a cementitious mix used to fix tile and stone floor coverings. It is also used to bond insulation boards to concrete substrates. You will find a wide range of tile adhesives on the market, but not all are suitable for use with underfloor heating.

It is important to use flexible tile adhesive for any application involved with underfloor heating. This is because changing temperatures will cause the adhesive to expand and contract, which would cause a standard tile adhesive to crack and damage your floor covering. Only flexible tile adhesives can withstand the changing temperatures generated by underfloor heating systems. Always check that your chosen tile adhesive is suitable for use with underfloor heating.

Tile adhesives vary in a number of ways, including their flexibility, consistency, colour, resistance to frost, how long they take to dry, and the maximum thickness they can be laid as an adhesive bed. The right adhesive for your project will depend on your floor covering; we always recommend checking with the floor covering manufacturer before choosing a tile adhesive to use with your tiles.

Tile adhesive is sold in bags as a dry powder and must be combined with water to form a workable mortar. All floor surfaces and insulation boards should be primed before they are bonded with tile adhesive. Priming ensures all surfaces are as smooth as possible, strengthening the adhesive’s bond with the substrate. It’s important to use a notched trowel when laying tile adhesive. Notched trowels ensure you lay your adhesive with suitably sized ridges, and prevent you using too much adhesive. An excess of adhesive can ooze up between the tiles and may allow your tiles to move. The tile adhesive will specify what size trowel to use when laying. Tile adhesive used for floor coverings must be left to dry for a minimum of 7 days before you switch on your underfloor heating.

The amount of tile adhesive you need for your installation will depend on your floor area and the depth of your adhesive beds. Typically, you will need a depth of around 3mm to bond insulation boards to your subfloor, with a layer of around 5mm required to tile over your cables. However, full instructions should be found in the manual of your chosen heating product.

You should never use more than 10mm of adhesive beneath your floor covering because this will insulate your heating system and allow less heat to rise into the room.

Levelling Compound

Levelling compounds are flowing, cementitious mixtures which are used to fill gaps and smooth uneven substrates. You will need to use a levelling compound to provide a flat surface if you want to fit a wood, carpet, vinyl or laminate flooring over a sticky mat or loose wire underfloor heating system. You may also wish to use a levelling compound if you are fitting a tile or stone floor covering. This can help protect the cables from damage while you are laying the tiles, and will ensure there are no voids or air pockets left beneath the tiles. Using a levelling compound before laying tiles is not essential, but does make the process much easier.

It is important to use a flexible levelling compound for all underfloor heating applications. This is because the compound must be able to withstand the changes in temperature generated by the underfloor heating system. Standard levelling compounds can crack when used with underfloor heating, which risks damage to both your floor covering and your heating system. Always choose a levelling compound which is advertised as suitable for use with underfloor heating.

Levelling compounds vary in a number of ways, including: strength, time taken to dry, ease of flow, suitability for use with different substrates, and the maximum depth which can be laid. The best levelling compound to use with your underfloor heating will depend on the substrate on which it will be laid. Check product specifications to ensure compatibility.

Levelling compounds are sold in bags as a dry powder and must be combined with water to form a free-flowing, homogenous mixture. Before laying, it is advisable to prime the substrate. This provides a smoother surface and increases the strength of the adhesive bond. The mixture can then be poured directly onto the substrate. You can use a solid bed trowel to create a smooth, level finish at the required thickness.

The required thickness of your layer of levelling compound will depend on your floor covering. A layer of 8-10mm is required if you want to fit carpet, vinyl, wood or laminate floor coverings over a sticky mat or loose wire heating system. A 5mm layer is recommended if you want to use the compound beneath tiles. Drying times vary greatly from one levelling compound to the next and can be found in the relevant product specification or manual.

Primer

Primer is a paint-like mixture used on flat surfaces as a preparatory coat before the application of tile adhesives and levelling compounds. Primer fills in small gaps and glosses over rough areas, creating a smooth, level surface ideal for strengthening the bond between surface and adhesive. It can also help prevent water penetration. We advise using primer on any layer of your underfloor heating build-up that will be bonded with tile adhesive or levelling compound. This may mean priming your sub-floor and both sides of your insulation boards.

Some primer brands developed specifically for use with underfloor heating will also boast of their insulative properties, helping to prevent heat loss through the floor. Whilst these primers may offer some benefits for the overall insulation of your system, this does not compare to the level of insulation provided by insulation boards or rolls; primer should be used in combination with, not instead of, insulation boards.

You will find a few different kinds of primer on the market. Make sure you choose a brand which is suitable for use with both your substrate and the tile adhesive or levelling compound you want to use on top. Full details of compatibility can be found on primer product pages.

Primer is easy to apply with a brush or roller and typically takes 1-2 hours to dry.

The amount of primer you will need will depend on the floor area of your project. You can check the coverage offered by different bottles of primer in their product specifications.

Dual Overlay

Dual overlay is a free-floating system of wooden boards designed to be used on top of foil mat heaters under soft floor coverings such as carpet and vinyl. Typically made from MDF, dual overlay is designed to provide a smooth and stable base, whilst protecting the cables from sharp objects such as table legs and shoe heels.

Dual overlay systems are fairly standard, with little variation between different products on the market. Note that when used with underfloor heating, dual overlay layers need to be thin to allow heat to pass efficiently through to the floor covering, so make sure your overlay system does not exceed a total of 7mm in thickness.

Installation is a quick and easy process that does not require the use of adhesives. It is important to lay the base layer first before laying the top layer above in a staggered, brick-like fashion. This prevents joints showing through your floor covering.

Note that dual overlay is not waterproof, so you should not use a foil heater combined with vinyl or carpet in a bathroom or wet room.

What’s the best underfloor heating system for bathrooms?

Bathrooms

Underfloor heating is a luxurious heating system for bathrooms, arguably the space where you’ll notice most the comfort of heated tiles on chilly winter mornings. Underfloor heating is also a practical bathroom heating strategy ideal for small bathrooms with limited wall space. It can also help those damp floors dry faster after baths and showers.

The best system for your bathroom will depend on a number of factors, including what type of floor covering you want to use and whether you want your bathroom to be a wet room. The critical difference between bathrooms and wet rooms is the way they drain water.

Bathrooms

In an ordinary bathroom, each water source will be its own self-contained fixture with an independent drain. Your shower will be enclosed and will have a shower tray which collects all the water and funnels it down the shower drain. Whilst your floors may get a little damp from time to time – especially if your bathroom caters for an entire family of splashy bathers who are none-too-careful with the bath mat! – they do not need to be engineered to collect and drain water.

This means, in theory, that you have as much flexibility to choose your bathroom flooring as any other room in your house. Whilst ceramic, stone and vinyl tiles are the most popular choices, it’s also perfectly possible to have a wood or even a carpeted floor in your bathroom.

As such, the choices for bathroom underfloor heating are similarly open-ended. All underfloor heating systems have very high IP Ratings to protect against ingress from water, which is a risk in any room in the house – whether through spills, soggy feet or floor mopping. This means all our underfloor heating systems are safe to use in bathrooms. The main thing to consider is whether any of the layers required for installation will react badly to frequent exposure to water.

The only type of system you are likely to have a problem with is foil mats fitted beneath vinyl or carpet floors. These systems require a layer of MDF dual overlay to protect the cables. The dual overlay should not be exposed to water over long periods of time because it can warp and soften. If you’re in any doubt, plump for a loose wire or sticky mat system under a layer of self-levelling compound; this will allow you to fit carpet and vinyl floors without the layer of overlay.

Wet Rooms

Wet rooms differ from bathrooms because they have water fixtures which are not self-contained. The shower – which may encompass one or more outlets of jetting water – will empty straight onto the floor. This means the floor must be engineered to collect and drain all the water in the room, without risking water spillage into the rest of the house. Fitting a wet room is a delicate operation which we don’t recommend undertaking DIY unless you’re absolutely confident with your skills. The floor must be carefully engineered to ensure it is fully sealed and banked at such an angle that water always funnels down the drain, rather than escaping into other areas of the house.

The only floor coverings which you should use in wet rooms are those which are water-repellent and non-porous – namely, tiled or stone floor coverings. For this reason, only loose wire and sticky mat heating systems are suitable for use in wet rooms.

Your wet room will also require a tanking system fitted beneath your floor covering which seals up any gaps between your walls and floors and makes an impassable seal which delivers all the water down your drain. If you already have a tanking system in place, you can simply fit your cables over the top. However, if you’re starting the project from scratch, it’s worth looking out for underfloor heating kits which include a tanking system.

For example, our Vario Pro Loose Wire Heating Kit includes both a reel of underfloor cable and a roll of waterproof membrane designed to function as a tanking system. The membrane is unrolled over the floor, where it is fixed with tile adhesive, and any are gaps bridged with sealing compound and sealing tape. The underfloor heating cables then slot into the grooves of the membrane. This provides a waterproof, fully tanked heating system with a much lower build-up than an equivalent system built over an existing tanking system.

Bathroom Thermostats

All underfloor heating systems must be monitored and controlled by an underfloor heating thermostat. When installing in a bathroom, the thermostat can be hardwired into the underfloor heating system but should be mounted outside the bathroom in a dry room – usually the hallway.

Thermostat wiring is not a DIY job. All aspects of underfloor heating wiring – including connecting the system and the thermostat to the mains – must be completed by a professional electrician.

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