We carried out suitability tests on microstructured plastic films for the integration into insulating glass units. As a result of our experiments UV-stabilized composite films are identified as best performing products for this application and chosen for prototyping a prismatic film with seasonal shading properties. Optical and thermal simulations conducted on a triple glazing incorporating the prototype film demonstrate the energy saving potential of this product, which provides a high solar energy gain in winter and efficiently prevents overheating in summer.

First large format glazing prototypes (ca. 850 mm x 700 mm) have already been manufactured and will now be exposed to both indoor and outdoor tests (Fig. 6). Laboratory tests will focus on the optical and thermal characterisation of the system as well as on the requisite durability of the film and the glass unit. Tests in real building aim at verifying both the theoretically predicted energy performances of the glazing and its practical reliability.

They play an important role particularly with regard to the application as transparent insulating material. Under operating conditions these components are exposed to extreme temperature and

irradiance regime, which are not Fig.6. Glazing prototypes installed on the facade of considered by standard long term test the ISFH experimental budding fOT °utdoor tests

procedures for insulating glass units.

Acknowledgment

The presented project is funded by the "Deutsche Bundesstiftung Umwelt (DBU)” with the reference number 24673. The authors gratefully acknowledge this support and carry the full responsibility for the content of this paper.

References

[1] Daniels, K., Bartenbach C. (1977), Tageslichtdurchflutung durch Sonnenschutz. Technik am Bau 3, 291-294.

[2] Critten D. L. (1988), Light enhancement using e-w aligned long prismatic arrays at high latitude. Solar Energy 41 (6), 583-591.

[3] Geuder, N., Klett, U., Fricke, F.(1998), Mikrostrukturierte Prismensysteme zur Solarenergienutzung. Tagungsbericht 11. Internationales Sonnenforum, Koln, Germany, 502-509.

[4] Hohfeld, W. et al. (2003), Application of microstructured surfaces in architectural glazings. Proceedings of Glass Processing Days, Tampere, Finland, 342-344.

[5] Christoffers, D. (1996), Seasonal shading of vertical south-facades with prismatic panes. Solar Energy 57 (5), 339-343.

[6] EN 410: 1998, Glass in building — Determination of solar and luminous characteristics of glazing.

[7] EN ISO 4892: 2001, Plastics — Methods of exposure to laboratory light sources — Part 1: General guidance.

[8] EN 1279-2: 2003, Insulating glass units — Part 2: Long term test method and requirements for moisture penetration.

[9] EN 1279-3: 2003, Insulating glass units — Part 3: Long term test method and requirements for gas leakage rate and for gas concentration tolerances.

[10] WINDOW 5.2, Lawrence Berkley National Laboratory (LBNL), San Francisco, http://windows. lbl. gov/software/window/window. html

[11] Christoffers, J., Deutschlander, T., Webs, M.(2004), Testreferenzjahre von Deutschland fur mittlere und extreme Witterungsverhaltnisse (TRY). Deutscher Wetter Dienst Verlag, Offenbach a. Main.

[12] Giovannetti F. (2006), Blendfreie saisonale Verschattung von Prismenverglasungen. 12. Symposium Innovative Lichttechnik in Gebauden, Kloster Banz, Germany, 60-65.