The working group „Warm Edge“ of the BF has held a research project in 2012 together with the institute for window technique (ift) in Rosenheim. The aim was to develop a new measuring method for the equivalent thermal conductivity. The producers of spacers may now issue new data sheet with the values measured on this basis. The data sheets of the old version (calculated) are not valid any more since January 1, 2014. Only data sheets with the measured equivalent thermal conductivity of the spacers are valid since this date.
Here you can download the current BF data sheets Psi values for windows easy and free for immediate use.
You can download the final report of the research project “Equivalent Thermal Conductivity – Warm Edge” of ift Rosenheim in collaboration with the Warm Edge work group of Bundesverband Flachglas here.
The BF-Bulletin 004/2008 – Modification index 4 – March 2017 Guide to ‘warm edge’ for windows is available here