Windows with improved energy performances

Jacob Birck Laustsen, Svend Svendsen

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


Heat loss through windows represents a considerable part of the total heat loss from houses. However, apart from providing daylight access and view, windows offer a unique potential for solar gain to be exploited during the heating season. Until now valuation of the energy performance of windows has primary focused on the heat loss coefficient, U-value. However, as the U-value, especially for the glazing part, has improved considerably during the last years, the total solar energy transmittance, g-value, has become equally important to the total energy performance of windows. Improved energy performance of windows can be reached by development of each element of the window, but to gain a considerable improvement in the overall energy performance all elements of the windows need to be examined together and the construction optimised. This paper describes potential improvements of window elements with respect to the overall energy performance of windows. By selecting some of the best solutions a new low energy window has been developed for high latitude climates and a prototype manufactured. Simple and realistic improvements such as reducing the frame width and using glass with low iron content have resulted in a window with a positive net energy gain (in short the Net Gain Window), which means that it contributes to the space heating of the building. All improvements are based on existing technology and manufacturing methods. The results from this work show that the energy performances of windows can be improved considerably in a fairly simple way without increasing the cost.
Original languageEnglish
Title of host publicationProceedings for ISES 2003 : ISES Solar World Congress 2003
Number of pages7
Place of PublicationGöteborg, Sweden
Publication date2003
ISBN (Print)91-631-4740-8
Publication statusPublished - 2003
EventISES Solar World Congress 2003 : Solar Energy for a Sustainable Future - Swedish Exhibition & Congress Centre, Göteborg, Sweden
Duration: 14 Jun 200319 Jun 2003


ConferenceISES Solar World Congress 2003 : Solar Energy for a Sustainable Future
LocationSwedish Exhibition & Congress Centre


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