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Underfloor Heating Explained - Important info for Customers 

The surface temperature of the floor must never exceed 27°C. This also applies to areas next to radiators and elements, under furniture and carpets, etc. With good furnishing and without too many carpets, or carpets that are too thick, it is reasonable to achieve a temperature of 23°C over the entire floor area, for a room temperature of around 21°C. Of course, this is assuming that the room requires a normal amount of heating. This means that your sealing, insulation, windows, etc., must be of regulation standard quality. Extra precautions should be taken to ensure the temperature at the feeding of the hot water never exceeds the maximum level, and that installation instructions provided by the supplier of the heating system are followed correctly.  Always increase the UFH temperature gradually, particularly when the floor has first been installed or after long periods of not using the UFH. Any wooden flooring will need to acclimatize and if the temperature is suddenly increased and run at very high levels then there is a risk of the flooring shrinking and the top hardwood layer developing surface will split and delaminate. 

When laying a floor over underfloor heating loops, the working temperature should be at least 18°C. This is applicable to boards, subfloors and room temperature. The relative humidity (RH) of the air must be between 30 and 60% before, during and after laying the floor.

Cardboard is preferred for the intermediate layer, as polyethylene cellular plastic foam fibre underlay and cork particleboard have a higher thermal resistance, are not fully breathable. 

Maximum Floor Top Surface Temperature in use: 27°

Maximum Floor Underside Temperature in use : 40°

Maximum Heat Output in use : 75W/m2

Subfloor / Room temperature at time of installation: 15-24°

Subfloor ERH (equilibrium relative humidity) at time of installation: 40-65%

RH ARH (ambient relative humidity) at time of installation: 40-60%

RH Maximum un-evenness of subfloor recommended: 3mm over 3m

Maximum M/C of floor joists & ply substrate (if applicable): 12%

Minimum distance of hot water pipes below boards (in screed): 30mm

Minimum distance of hot water pipes below boards: 3mm

Maximum joist spacing (if applicable) 400mm

Minimum Edge Expansion joint: 12mm

Thermal conductivity of Tectonic 20mm boards: λ = 0.17 W/mK

Thermal conductivity of Tectonic 15mm boards: λ = 0.17 W/mK

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