Fensterlüfter in der Gebäudesanierung

Passive window ventilation openings for building refurbishment.

A thorough building refurbishment generally includes window replacement and thermal insulation of the opaque building envelope. However, quite often only a window replacement is done and the building envelope is left uninsulated. If there is no mechanical ventilation system installed which ensures continuous air exchange, new airtight windows usually lead to a reduced infiltration air exchanged and subsequently there may be moisture damage. A possible solution could be the integration of passive window ventilation openings (PWVO). This raises two questions: Firstly, can PWVOs guarantee the necessary ventilation rate to avoid moisture damage? Secondly, how do PWVOs compare to a ventilation system with heat recovery in terms of heating demand? This Article deals with passive window ventilation openings without heat recovery in flats with cross ventilation. Based on transient building simulation of a typical dwelling unit it is shown that the PWVOs by themselves cannot guarantee a sufficient ventilation rate for moisture control. With additional exhaust fans in the kitchen and bathroom(s) the required ventilation rate can be achieved. However, PWVOs with high air flow rates (approx. 15 m³/h at 2 Pa) must be used. Compared to PWVOs the installation of a ventilation system with heat recovery leads to energy savings of approx. 20 % in an uninsulated building. In a building where the building envelope has also been insulated, the savings would be approx. 60 %.