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Uw-value tests on VELUX, 
FAKRO, Roto and Keylite products

The results of Uw-value tests on our own and competitors’ products, made by the global consultancy Navigant at two different European notified test institutes during 2016-2019, found discrepancies between the declared Uw-values and the tested products’ Uw-values. We brought these findings to the attention of our competitors as well as to the relevant market surveillance authorities in July 2018 and we have followed up with new results since then.

The VELUX Group presented solid documentation to authorities and continued the testing of our own and competitors’ products in end of 2018. Except from a few tests the new tests in 2018 and 2019 showed same discrepancies between the declared Uw-values and the tested products’ Uw-values as before. We  have now tested between 10 and 30 samples for each individual product variant. Except from one Roto variant it seems that the test results indicate that the tested products brought to market by our three competitors, FAKRO, Roto and Keylite, to a large extent, do not comply with their declared Uw-values. Se all results below.

We believe this is an industry matter and that transparency about the state of Uw-values is paramount to creating a level playing field in the roof window industry. We want a fair roof window marketplace with a good reputation, so that consumers can rely on the qualities of the roof windows they buy as holding true. Therefore, we have made the results of tests by independent notified testing institutes ift Rosenheim, Germany, and Centrum Stavebního Inženýrství a.s., Czech Republic available below. Furthermore, we will continue testing products in the coming years. The tests were carried out in accordance with the European standard (EN ISO 12567-2) for testing Uw-values of roof windows, using the reference roof window size. The roof windows were installed in the test boxes in compliance with the respective manufacturers’ guidelines. Therefore, we believe that the test results reflect the actual value.

Contact us for more information on the tests >

  • Tested FAKRO products

    Tests at: ift Rosenheim. Product: FAKRO FTP-V U3 

    Uncertainty of measurement is from +- 0,07 to +- 0,09 W/m2K depending on test
    In July 2018, FAKRO redeclared the Uw-value of FTP-V U3 from 1,2 W/m2K to 1,3 W/m2K after being notified about the test results.

  • Tested Roto products

    Tests at: ift Rosenheim. Product: Roto WDF R88C K WD AL

    Uncertainty of measurement is from +- 0,06 to +- 0,08 W/m2K depending on test




  • Tested Keylite products
  • Tested VELUX products

    Tests at: ift Rosenheim. Product: VELUX GGU 0070

    Uncertainty of measurement is from +- 0,06 to +- 0,09 W/m2K depending on test
    Note*: “Windows 1, 2 and 3 in 2017 were not sourced through a dealer but sampled from the VELUX warehouse, and they were tested first at CSI, then at ift.


    Tests at: ift Rosenheim. Product: VELUX GZL 1051

    Uncertainty of measurement is from +- 0,07 to +- 0,08 W/m2K depending on test

    Tests at: Centrum Stavebního Inženýrství a.s. (CSI). Product: VELUX GLU 0051

    Uncertainty of measurement is +- 3%