Energy Saving by use of Active Roof Windows

Bruno Harald Philipson

On the basis of new and existing residential buildings around Southern Europe, a study on the effect of passive systems for heating and cooling, by the use of dynamic roof windows systems, has been carried out by CSTB and VELUX A/S. The study has been made for typical existing residential buildings in Spain and for low energy housing in Italy. The technology studied utilizes the passive solar energy through roof windows and actives the insulation shutter when needed, thus reducing the heating requirement during the heating season while optimizing the daylight conditions. For the summer situation, when the buildings need to be shaded, the intelligent and passive window systems will activate natural ventilation through the windows or/and the solar shading, thus optimizing the indoor climate while reducing the requirement for cooling.

The study was carried out with two different types of simulation software, BSIM2002 by VELUX A/S and SIMBAD by CSTB. The simulations were carried out independently of each other.

The findings from the study show that in both new low energy housing and existing residential buildings in Southern Europe, the use of energy for heating and cooling will be reduced by installation of roof windows with the use of “passive” strategies and technologies. The study also show an improved indoor climate in the building, where the indoor temperature can be kept at a lower level after the use of the technology without increasing the need for cooling, as well as improved daylight conditions in the building.

The intelligent passive roof window system, consist of an intelligent control of the external solar shading and intelligent control of the opening and closing of the roof window. The intelligence lies in the optimizing the use of the passive elements to reduce the need for heating and cooling, before the installed heating, cooling and ventilation, systems are activated, while the user finds it logical. This is done automatically without feedback or control from the user. It is very important that the user finds the passive elements logic, otherwise the user will overrule the intelligent control, and thereby minimizing the possibilities for reduction in energy and optimizing the indoor climate.

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