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The thermal insulation of a front door

The thermal efficiency of a front door is defined by its Ud. Bel'M returns to this value to explain how to select the level of thermal insulation according to your home.

What is the thermal insulation of an entrance door?

The Ud factor lets us measure the thermal insulation provided by the front door:

  • U for insulation factor. The lower the value the better the insulation.
  • d for "door" indicates the product it's calculated for.

This factor is expressed in W/m².K (watts per metre squared kelvin). That is it evaluates the energy (W) that crosses the door and which depends on its surface area and the temperature difference  between the outside and inside (m².K). The lower this factor, the more your door is insulating.

For the most insulating doors the Ud is generally 1 and can rise to 4 for old doors. Such a high factor can explain the temperature differences between the entrance and the rest of the house. The higher the Ud, the greater the heat losses and the higher the energy consumption .

Replacing a door with Ud 1.6 by a door with Ud 1.1 W/m².K means reducing energy losses by 30%.

On the website, each model is assigned a Ud factor, which is calculated in accordance with standard NFEN14351-1 (green value at the top of the product sheet). This value is taken into account for Tax Credit.

A second value can be seen in the "Insulation" tab, this is the Ud calculated according to the standard dimensions of an entrance door, i.e. H2150 and L900mm.

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