Contact us

Hi! Do you have a question? Leave a message below and we will get back to you as soon as possible!


Here you will find contact information for our offices and showrooms in different locations.

Decorative ArrowLoading...


It is statutory in Europe that all climate-separating products (windows and doors) must be CE certified. This means that you as a manufacturer must provide declarations of performance where the mandated characteristics are reported. The purpose of this declaration of performance (DoP) is that consumers and customers should be able to compare products from all European manufacturers on equal terms, tested in the same way via accredited institutes. It is very variable how suppliers choose to report these test results. Therefore, it is very important that you as a door or window buyer always ask for declarations of performance in order to make a relevant comparison of tested facts. On this page, we explain performance and show how Ekstrands compares to the requirements of national labeling systems.


The U-value indicates how well a product insulates (keeps heat and cold out). The lower the U-value, the better the product insulates. What defines a good U-value depends entirely on where the window should be located. In old houses where walls and roofs leak a lot of energy, the U-value around 1.0 - 1.3 is enough to increase comfort indoors. If, on the other hand, you build a passive house that is to be self-sufficient, the U-value should fall below 0.80.

For windows, Swedish P-marking requires that the value be declared, thus no specific requirement for thermal insulation. SFDK requires ≤ 2.0W/m²K.

U-värde fönster


The G-value shows how much energy is transferred through direct solar radiation. The higher the value, the more energy and thus heating it generates (windows account for about 30% of heating in houses).

To think about here is how much heating you want through windows to the house. If you have large glass surfaces in dense newly built houses, it can be good to look at a lower G-value so that you do not have to cool down the house on hot sunny days. Also think about the location of the window in the latitude, and how much solar energy reaches the window.

Solenergi fönster


The daylight transmittance is stated as a percentage and is a measure of the amount of daylight that enters through the window. A high daylight transmission is preferable, then it is experienced brighter.

Dagsljustransmittans på fönster

Safety against wind load

Safety against wind load is stated from A1 to C3. Wind load is tested in two steps. Frame deformation is stated in class A-C where C is best. Indicated in combination with pressure class 1-3 depending on how hard the product has been tested under, where 3 is highest in Sweden. For class 3 it is 1200 pascals. After that, you finish with a safety test with 1.5x higher pressure (1800 pascals for class 3).

Safety against wind load on windows

Water tightness

Rain density measures how well the product seals against rain. Windows are listed in class 1A-7A where 7A is best.

A means that the product has been tested in unshielded condition, B shielded. At pressures above 600 Pa, class Exxx is specified, eg E900.

Water tightness on windows

Air permeability

The air tightness indicates how well the product withstands air pressure. Listed in class 0-4 where 4 is best. Both class 3 and 4 are tested below 600 pascals, but in class 4 a third less leakage is allowed.

Air permeability windows