December 27th, 2014. Without doubt, an excellent thermal insulation is one of the most efficient measures to reduce energy consumption of buildings. As a consequence, windows and facades, key components of building envelopes, have to provide even better (lower) U-values. My latest article published in issue 12/2014 of German glass magazine GLASWELT here discusses the consequences for the development of warm edge systems (article is in German language).
December 9th, 2014. The office of the Consultant for warm edge and glass has been moved from Herrenberg to Boeblingen, closer to the captital of the German federal state Baden-Wuerttemberg. Please note the new contact data at the bottom of these pages.
As soon as everything is unpacked, you will find here again regular contributions to the subject of thermally improved insulating glass spacers, glass and other related topics.
July 11th, 2014. It is a persisting opinion amongst some window producers, that warm edge would only have marginal influence on the heat loss through a window. Quote from the interview with a window manufacturer, printed in the German glass magazine GLASWELT 5/2014, page 58: “Und so viel Energie geht doch nicht über diesen Kanten-Unterschied verloren.” – “And it is not that much energy that is lost through that difference in edge bond.“
Good gracious! Maybe this was valid in former times, when thermal transmission coefficients of windows were on rather humble level. For window U-values of more than 2 W/m²K, the improvement by use of warm edge systems was not that much. During the past years though, windows went through an enormous evolution in thermal performance. Nowadays, Uw-values of windows for new buildings in Germany are in the range of approx. 1.1 to 0.8 W/m²K, and this Uw-value is for the whole window, including frame and thermal bridge at the glass edge – not only a center-of-glass value. By rule of thumb, the use of warm edge instead of conventional aluminium or steel spacers improves the Uw-value of wooden- or PVC windows by approx. 0.1 W/m²K – or for metallic windows up to 0.2 W/m²K. Considering that approximately reveals that the effect of warm edge is easily in the range of 10 % – of the overall energy losses through a window, note well!
But for all that, in new windows aluminium spacers still do occur, even if it is triple glazing. What a pity, to pass up the chance for improving the Uw-value. Why? Is it just a lack of knowledge or making false economies? After years of educational work on this area I have no more understanding for that. Compared to other measures for thermal optimization of windows, warm edge is simple to implement and in addition extremely economical. Once the new windows are installed without warm edge, they will stay like that for the next decades. The potential for energy saving is lost for a long time.
This graph shows the energy losses of a single-winged window and how they are shared between the three window components glass, frame and edge bond. Furthermore it illustrates the potential for optimization. Starting point is a window with the dimension 1.23 m x 1.48 m, a frame share in the total window area of 30 %, an Uf-value of 1.2 W/m²K and triple glazing with an Ug-value of 0.7 W/m²K and edge bond with aluminium spacers.
The comparison shows the possible extent of improvement of the Uw-value through
– warm edge instead of conventional aluminium spacers
– improvement of the Ug-value of the glass area
– improvement of the Uf-value of the frame area
If you want to know more about that, you can read my article (in German language) in the
GFF-magazine of march 2014 here .
June 16th, 2014. During all those discussions about the third position after the decimal point of Psi-values, sometimes I miss other important aspects of insulating glass, like for example the durability of the edge bond. World’s best warm edge system would be worth nothing, if it allows for the gas fill to leak from the gap between the panes, because this worsens the Ug-value. Or if the unit fails untimely, because humidity can get into the gap and condensate on the inner glass surfaces. In my latest article for the magazin GLASWELT, I explain what is important for the processing of warm edge spacer systems and for the quality of insulating glass units. You can read the article in German language here.
February 11th, 2014. In the newsletter ‘e-transparent’ of December 2013, the German association Bundesverband Flachglas had published a legal experts comment to the question whether warm edge would be “state of the art” and what this would imply for the obligation to advise clients properly in Germany. In a contribution for the journal GLASWELT, I picked up the matter and explained the different technical standards. You can read, why you are well advised with warm edge in my article here (in German language).
January 9th, 2014. The English versions of the ift guidelines to “Warm Edge” are available now for purchase from the new ift online-shop for literature:
January 6th, 2014. With the following webinar topics, again, I will take an active part in the seminar program of the BF Bundesverband Flachglas for spring/summer 2014:
These online tutorials are all held in German language. They take approximately one hour each and shall give a first overview about the topics. More in detail and furthermore available in english language as well are my on-site-workshops.
Information about the BF-Webinar-program is available here (in German):
https://www.bundesverband-flachglas.de/veranstaltungen/webinare/technik/webinare.html
January 6th, 2014. This is just to remind on time, at the beginning of 2014, that old BF-data sheets “Psi-values for windows” with representative Psi-values simulated from individual material values have lost their validity. According to a decision of the BF Working Group “Warm Edge”, from now on only data sheets with Psi-values determined with the measured equivalent thermal conductivity of the spacer are valid.
My recommendation: Do not save data sheet copies locally on your computer. In case of need just download the data sheets always newly from the website of the BF Bundesverband Flachglas. This will ensure that you are always up-to-date.
You can find the link on my literature list, or directly here.
September 2nd, 2013. The final report of the research project “Equivalent thermal conductivity warm edge” is now available in english. You can download it for free from the websites of ift Rosenheim here.
August 12th, 2013. According to latest information from Rosenheim, the translations of the new ift-guideline WA-17/1 dated February 2013 and of the revised guideline WA-08/2 dated July 2013 still are a long time in coming. Further delays will make them available not before end of August.
Come around regularily, I will keep you informed at this point.
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