High Specification Thermal Backer Boards Are Vital For Underfloor Heating

Published: 02nd February 2009
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How Run Your New Electric Underfloor Heating Economically.

Most electric underfloor heating systems are capable of providing safe and economic heating.However there is a lot of confusion regarding claims by some suppliers of heating mats who maintain that theirs is an ultra efficient cost saving version.

The fact remains that 1kw of electricity will produce 1 x kw of heating. This means that a 20 square meter floor area using 130w heating mat will produce 2.6kw of heating

The secret of getting economical heating is to start with a high specification insulation layer. The underfloor heat up time is determined by the thermal conductivity of the sub-floor that it is laid on

It is therefore vital that a thermal backing board is fitted over the sub- floor before the heating mat is fitted. This should have a thermal conductivity of 0.027(W/mk) and a U value of below 3.5 (W/m'K)

This thermal conductivity is a calculation of the rate at which a material will pass heat energy. This is measured in watts per square meters per degree of temperature difference (watts ' meters) per degree of temperature Using a high specification thermal board will force the heat upwards instead of letting it disperse back down through the sub-floor, meaning that far more of the heat that the matting is generating is in turn heating the room.

This ensures that the heating thermostat can be turned down by the corresponding degrees, thereby saving power and electricity costs.

It is also a consideration that high thermal conductivity below the heat matting helps to give a fast warm up time of the floor surface -less than 20 minutes can be achieved.

Thickness of the insulating backer board will have a bearing on the thermal resistance. A thicker board having a greater thermal resistance than a thinner one, so if final floor height is not an issue, then go for the thicker board every time. You will also find that there is very little price difference between the board thick nesses. This is because the face material of the board and the manufacturing labour is the same regardless of board thickness.

When choosing an insulating backer board, compressive strength kPa is very important. Look for a board with a high rating over 300 kPa as this will ensure rigidity sufficient to support the weight of the heat mat, adhesive, floor tiles and any heavy appliances or furniture that will be standing on the floor. 300kPa is in fact equivalent to 30 tones per square meter.

The facing of the board should be a consideration. A fiberglass scrim on either side of the board, coated with a polymer will assist in adhesion of the tile adhesive as well as ensuring increased structural stability. This also means that the boards can effectively be used to level up old uneven floorboards. This can be an alternative to over-boarding the floorboards with expensive plywood which has little thermal resistance. However if the sub-floor is flexing, a plywood layer may be the only option.

The boards can be cut and installed extremely quickly. They can usually be cut with a Kraft knife and can be screwed into a wood floor, or bonded onto a solid substrate with a fast setting flexible tile adhesive.

To summarize.

1. Do not lay your heating without a thermal backing board- it will waste electricity and money in the long run.

2. Buy waterproof boards that have at least 0.027 W mk thermal conductivity and a compressive strength of over 300kPa.

3. Buy boards that are mesh backed on both sides- these are slightly more expensive than un-backed boards, but will perform better.

Alan is the technical manager at Birbek Floors Ltd, a UK distributor of insulation for electric underfloor heating and insulating tile backer boards

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