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Theromonet Underfloor Heating FAQ

Please note that the below FAQ's are supplied by Thermonet, of which Leafcutter Design is a stockist. In the FAQ questions on this page, 'we' refers to Thermonet, the manufacutrer of the underfloor heating mats avaiable online through our store.


What is Thermonet?

Thermonet is a quality heating element stitched to a fibreglass mesh to create a fixed output either 150W/M2 or 200W/M2. IT is incorporated into a cement based adhesive or screed.

Will it heat the room?

Thermonet 150W/M2 can be used to take the chill off your floor or to heat the room. Thermonet 200W/M2 is recommended for conservatories. Ask your stockist for advice on the best system to use.

Can Thermonet heat 100% of the floor?

Yes, whatever the shape and size of your room. Thermonet can heat your floor all over. For more complex installations the heatmats quickly convert into a fully flexible single wire system.

Does it add any extra height to the floor?

Virtually none. Under a tiled floor the heatmat disappears within the adhesive bed. Nominal height 2.5mm.

Does fibreglass mesh affect the floor in anyway?

Yes, it improves the strength of the floor as it becomes a reinforcing layer in the adhesive.

Do I need to cover the heatmat with a levelling compound?

Not always. It can be directly tiled over, but if you want a soft floor covering inc. laminate floors you must cover the mats with a fibre reinforced levelling compound.

Can it be laid on a timber substrate?

If the floor is ready for tiling, i.e sound and dry just lay Thermonet and tile, if the timber is not sound use Dukkaboard or 18 mm ply to reinforce the floor prior to laying Thermonet.

Can it be laid on a concrete screed floor?

Yes, we recommend that you check that the floor is insulated to ensure the system is efficient to run and you reduce potential heat loss.

Do I need to prime the floor?

No, you do not need to prime the substrate unless the adhesive manufacturer requires it.

Are all adhesives suitable for use with Thermonet?

No, we recommend the use of a polymer modified cement based adhesive, not a rubber crumb type. Always check with the adhesive manufacturer for suitability with underfloor heating.

Do I need to use conduit for the sensor?

Yes, it facilitates the change of a sensor if it is ever necessary.

Is it safe for use in a bathroom or shower?

Absolutely, the wires are encased in a double layer of tough waterproof insulation with a continuous earth braid fot total protection. Every system is factory tested and certified to meet the highest safety standards.

Can the cold tails be extended or shortened?

Yes, either with blue or brown connection wire or standard electrical cable. Take care to separate the earth braid from centre core.

Can the sensor wire be extended or shortened?

Yes, either it can be shortened or extended with twin core flex 0.75mm or similar upto a maximum of 50 metres.

Can Thermonet be used under any floor finish?

Subject to manucturer’s recommendation Thermonet can be used with most floor finishes, including stone, ceramic, porcelain, laminates, engineered timber, carpet, vinyl and so on.

If it under the floor, what happens if it goes wrong?

Thermonet is completely maintenance free. Once installed, it can’t go wrong. For peace of mind, we give you a 10 year warranty. If any damage occurs, the point of damage can be traced to within 50 mm and the system can normally be repaired in-situ.

How long will it take to heat the floor?

Insulated floors heat faster than un-insulated floors. The type of floor finish can make a difference too. If your floor is un-insulated, using Dukkaboard will reduce floor heat-up times and the system will cost less to run.

How much does it cost to run?

In a well insulated room (insulated upto current building regulations) it will cost around £6-8 per m2/per year. This assumes that the system is controlled by a programmable thermostat and set to approx 24 C, however, this is only indicative as there are many variables involved. For a more in depth calculation, please contact us for consultation with a heating engineer.

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