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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 efficient a building element is, at reducing 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 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, which combine to give the overall thermal insulation performance for the building.

Thermally rated steel doors are a key factor in building design, as their inclusion contributes to the overall building insulation performance, alongside ensuring compliance with standards and building regulations. Another advantage of a Thermally rated door is that is 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 which will be used on an office with people inside, keeping the heat in here 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, however will likely come at an increased cost and slightly extended lead time).

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


Are there any legal requirements for minimum ratings?

Yes, depending on the application there are regulations which 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 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.

Still not sure what you are looking for? Feel free to call one of our steel door experts for more information and advice!

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