Experimental investigation of downdraught from well-insulated windows

Since the climate in the Nordic countries is cold for several months a year, windows are crucial in building envelopes. The current trend to reduce heat losses by building components has resulted in many modifications to window design in order to improve thermal performance and the indoor climate. Improvements in window construction have resulted in a higher surface temperature on the inner pane and considerably lower downdraught, which in turn has created an opportunity for the unconventional design of the heating and ventilation systems. The impetus for this paper is to experimentally investigate the effect of thermal performance, window bay and displacement ventilation on the downdraught. The measurements show that the use of well-insulated windows, besides lowering energy consumption, gives rise to a higher quality of indoor climate. The results show a considerably reduced velocity and turbulent intensity by employing a well-insulated window instead of a conventional one. The influence of the window bay on the downdraught is also shown in the paper.