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What is a U-Value and why does it matter for steel doors?

Riverside Enterprise Park Lincoln3

A u-value measures how efficiently a building element reduces heat loss. Lower is certainly better when it comes to a U-value. The lower the value, the more effective it is in keeping the warmth in and the cold out.

It’s not only steel doors which have thermal properties measured by a U-value, every building is made up of lots of elements, each with their own U-values. All these elements will combine together to give the overall thermal insulation performance for the building.

Another advantage of a thermally rated door, is that it reduces the chance of condensation building up on the inside of the leaf.


What U-Value do I need for my Steel Doors?

Depending on the application for a project, your required thermal rating/ U-value will be different.

For example, if you are looking for a steel door used in an office with people inside, keeping the heat in is key! In this application, we would recommend a Rockwool core which has a U-value of 1.9 or our Climador range with an even lower U- value of 1.6 (Don’t forget the lower the number the better the insulation value).

Whereas if you are installing a steel door in an unheated space, the thermal rating may not be as important, therefore our standard honeycomb core could be most suitable.


Are there any legal requirements for minimum ratings?

Yes, depending on the application there are regulations which will state the minimum U-value required for new dwellings and commercial buildings. Steeldor thermal was developed to comply with these door efficiency targets stipulated by the government in The Building Regulations 2010. The leaf has an insulated, internal Rockwool core enabling it to achieve a U-value of 1.9, compliant with the guidance of 2.0 for new dwellings and 2.2 for new commercial buildings. These door-sets meet the standards set out in the 2010 approved documents L1A and L2A.

We always recommend that you check with your building regulation compliance inspector to ensure you are specifying the correct U-Value for the use of the building.

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