Development and Investigation of Evacuated Windows Based on Monolithic Silica Aerogel Spacers

  • Svendsen, Svend (Project Manager)
  • Jensen, Karsten Ingerslev (Project Participant)
  • Schultz, Jørgen Munthe (Project Participant)
  • Mølholm, N. B. (Project Participant)
  • Fricke, J. (Project Participant)
  • Chevalier, J. L. (Project Participant)
  • Achard, P. (Project Participant)
  • Pajonk, G. (Project Participant)
  • Durant, M. (Project Participant)
  • Henning, S. (Project Participant)

    Project Details


    The objective of the project is to develop and investigate insulating glazings based on evacuated monolithic silica aerogel spacers. Monolithic silica aerogel is a highly porous material (pore volume 90%) with an equivalent typical thermal conductivity of 0.020 W/(m K) when air filled. If evacuated below 50-100 hPa the thermal conductivity is only 0.008 W/(m K) which is approximately 20% of the value for commonly used insulation materials. However, the silica aerogel has to be protected against liquid water, that will demolish the pore structure of the material. For the application in window glazings the protection against liquid water is formed by placing the aerogel in between two sheets of glass and sealing the rim.
    The project has been carried out in co-operation between institutes and companies in Denmark, France, Germany and Sweden. The improvement of the production process has as the main goals to develop a safer process than the traditional one and to improve the optical quality of the monolithic silica aerogel. The thermal properties make the monolithic silica aerogel an excellent material for insulating glazings. Using the material as spacer between two layers of glass with a vacuum tight sealing of the rim combined with an internal gas pressure below 50-100 hPa result in an insulating glazing having a heat loss coefficient comparable with that of the surrounding wall, but at the same time offers a large solar heat gain possibility. However, the rim seal is the crucial point as it has to be airtight and vapour tight, but it may not become a serious thermal bridge that destroys the total performance of the glazing. Development of an airtight and vapour tight rim seal with negligible thermal bridge effect is one of the main goals in the project.
    Effective start/end date01/12/199231/12/1996

    Collaborative partners

    • Technical University of Denmark (lead)
    • Centre Scientifique et Technique du Bâtiment (Project partner)
    • Scan-Gobain Glass A/S (Project partner)
    • Airglass AB (Project partner)
    • Universität Würzburg (Project partner)
    • Universite Claude Bernard Lyon 1 (Project partner)
    • Produit Chimiques Auxiliares et de Synthéses (Project partner)
    • Mines Paris - PSL (Project partner)


    • Unknown


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