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This is one of the most common questions we’re asked! Many people assume that underfloor heating only works with hard flooring such as tiles and laminate, but carpet is also a suitable floor covering choice for underfloor heating. There are just a few considerations that need to be taken into account to ensure your underfloor heating still works efficiently when using carpet.

Laying carpet over your underfloor heating system does have it’s benefits but you must consider the type of carpet you are going to use, tog ratings, carpet underlay and more before installing an UFH system. This is because all of these factors will have an impact on the way in which your heating system works, so installers must make certain adjustments to ensure your UFH still warms your room effectively.

The benefits of using carpet with underfloor heating

There are many benefits to using carpet as your choice of floor covering for underfloor heating. Not only can it make a room feel extra cosy, there are actually certain hygiene benefits also.

For some rooms, such as bedrooms, you want them to feel as warm and inviting as possible. Hard flooring, like laminate, is not always the ideal choice to do this. Carpet on the other hand is soft and warm underfoot, giving rooms a cosy feel. By laying carpet over underfloor heating, if installed correctly, your room will be heated from the floor up for a warm, comfortable feel.

In addition to this, carpet tends to absorb dust. Using radiators as your choice of heating can cause this dust to circulate around the room. This is because radiators work by heating up the air in the room, which then begins to circulate and can release the dust particles and impurities from the carpet. Dust particles in the air can cause coughing, sneezing and itchy eyes, and may be especially bad for those with asthma or allergies. Underfloor heating, on the other hand, offers a healthy way of heating your home, as it does not cause air to circulate. Subsequently, this helps to make sure any dust absorbed by your carpet does not enter the air.

Carpet with underfloor heating

What types of carpet are suitable for underfloor heating?

While carpet is a suitable choice of floor covering for underfloor heating, there are certain types of carpet that should be avoided. If a carpet is too thick, the floor will be too well insulated for you to feel the benefit of your UFH system in the room. Certain carpet backings can also affect the ability for heat to travel through the carpet into your room.

Carpets with hessian backing rather than rubber, are recommended for use with UFH systems. Although they tend to be more expensive, the hessian allows heat to travel through the carpet whereas rubber acts as an insulator, keeping heat beneath the floor. This will stop it from effectively heating your room.

As mentioned above, you should also consider the thickness of your carpet. The thicker a carpet, the more insulation it will provide therefore reducing the efficiency of your underfloor heating system. You can decipher whether your chosen carpet will be suitable for underfloor heating via its tog rating.

Carpet tog ratings for underfloor heating

Tog rating is a measure of thermal resistance. When looking at tog ratings, you need to take into account the rating of both the carpet and the carpet underlay. The combined value of the carpet and underlay should not exceed 2.5 tog, and preferably less than 1.5 for systems with a heat pump.

It makes sense to take care in choosing carpet and underlay that will work well with the underfloor heating. Quality manufacturers will have technical information on their products available to customers so you can make the right choice.

As an example, the tog value of Brinton’s ‘Bell Twist’, a typical 80% wool and 20% nylon carpet, is 1.23. Most nylon pile carpets will achieve around 1 tog and the thickest wool carpets, over 2.5 tog. Accordingly, the thickest 80% wool and 20% nylon carpets should only be used after taking advice from both Nu-Heat design engineers and the carpet suppliers.

The tog of the carpet underlay chosen will then also need to be added to the tog rating of your carpet to calculate the overall tog rating. If this exceeds 2.5 tog then it is likely that your UFH system will not perform effectively.

Interfloor underlays Thickness Tog rating
Technics 5 5.0mm 0.56
Technics 6 6.00mm 0.66
Willow Green waffle rubber 8.4mm 1.1

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Carpet underlay for underfloor heating

Consideration should also be given to the underlay used to ensure its tog rating is taken into account at the design stage – most suppliers provide this information.

When choosing carpet underlay for your underfloor heating:

Do:

  • Choose an underlay that when combined with your carpet has a tog rating of under 2.5 tog.
  • Choose an underlay that has good insulation and noise reduction properties.
  • Choose a durable underlay that will help to protect your carpet.

Don’t:

  • Choose a super thick underlay. Although they may feel soft and springy underfoot, they are likely to have a higher tog rating.
  • Have a one size fits all approach. Different underlays might be more appropriate for different rooms.

Interfloor

Interfloor (manufacturers of Tredaire and Duralay) state that most of their underlay products are suitable for use with underfloor heating, Heatflow being specifically designed for the purpose.

Tredaire Technics

Tredaire Technics sponge underlays with polyester facing and glass-reinforced crepe paper backing have tog values of between 0.56 and 0.66 depending on thickness.

Best carpets for underfloor heating

The Brinton’s Bell Twist carpet is ideal for underfloor heating, with an average tog rating of 1.23. This means that when combined with underlay, the overall tog rating is usually still below the 2.5 tog threshold for underfloor heating. Generally, this is the case with all nylon carpets therefore when looking for a carpet suitable for UFH this may be the way to go.

Wool carpets may feel more luxurious but they tend to be thicker and achieve a much higher tog rating. Due to this, you will likely not feel the benefit of your underfloor heating if you choose to opt for this style of floor covering.

Carpet with UFH

How do I install carpet over underfloor heating?

You cannot fit the carpet as if the UFH system is simply not there, you will need to make certain preparations to ensure the heating runs effectively.

Factors to consider when installing a carpet over underfloor heating:

  • Ensure that the overall tog rating of the carpet and the underlay combined does not exceed 2.5.
  • Check that the floor is structurally sound and dry.
  • Ensure that any chemicals used on the floor, such as finishes and sealants, are compatible with your carpets underlay.
  • Remove any paint, debris or dust before the carpet is laid.
  • If there are any surface irregularities, these will need to be primed first. If you are laying over floors with gaps between the board, plywood may need to be placed over the top.
Maximum temperatures for under carpet heating

Maximum temperatures for under carpet heating

The maximum floor temperature should never exceed 27 degrees celsius. Most UFH systems will have restrictions in place to ensure this temperature is never reached and most rooms will not need a heat output anywhere close to this.

“To limit discomfort to residents, and to protect floor finishes from damage, BS EN1264-2[1] limits the maximum temperature of the floor surface to 29°C. It should be noted that lower maximum temperatures are required for certain flooring materials” – NHBC Foundation

The heat requirement of your room will depend on a number of factors including insulation, the purpose of the room, floor covering choice etc. This is why it is important to know the tog rating of your carpet and underlay to ensure the system is set at the correct temperature. You can then control your heating system using a thermostat.

Using a thermostat with under carpet heating

There are many different thermostat options including simple dial thermostats, digital displays and even smart thermostats. If you choose to use carpet as your UFH floor covering choice, a thermostat is essential to maintain a comfortable temperature in your room.

Carpeted rooms tend to be warmer, therefore you may find that you do not need to have the temperature as high as in other rooms. Alternatively, you may want to create a cosy warm environment by raising the temperature of the room. Whatever your preference, you can easily control your UFH system with your thermostat.

Is using underfloor heating and carpet safe?

Laying carpet over underfloor heating is completely safe. As long as your UFH system has been installed correctly by trained professionals, then you have nothing to worry about!

Our underfloor heating services are completely bespoke, and we make sure your system is suited to your needs. We can also put you in touch with one of our registered installers to fit your system, offer advice and support before, during and after your project, so you can be sure it is safe and fit for use.

Get in touch for more information or to get your bespoke quote.

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