Overall evaluation of windows - possible improvements within 5 years

Furthermore the problem of outside condensation on super insulating glazing has been addressed. Several measures for energetic improvement of windows i.e. increased solar transmittance (low iron glass, anti reflective glass, slimmer frame solutions) and lower U-values (triple glazing, insulating glazing rim seals/spacers, frames with built-in insulation) are already available on the market. Detailed analysis of the increased risk of over heating caused by use of improved windows shows a significant energy saving potential but it is essential to include automatic controlled solar shading devices and/or venting and night cooling by outside air. An economical evaluation of the different technical options shows that only the warm edge solution for sealed glazing units and the anti reflective glass solution are profitable. Application of triple glazing will only be energetic favourable if combined with use of low iron glass, but this makes the solution too expensive at the present. It has not been possible to economic information for improved frame solutions e.g. the German 'Passiv Haus' windows. A computer program has been developed for investigation of different measures to reduce the risk of outside condensation. The most promising solution is a low emissive hard coating on the outer glass surface, which eliminates the problem but result in a decreased solar transmittance. Overhangs leads to significant decrease of the condensation problem but influences the architectural expression of the building