Subjective reactions to daylight in rooms: Effect of using low-emittance coatings on windows

Abstract

In this study, the impact of two different types of window glazing using two identical rooms was studied. In one experiment both rooms were furnished as an office, in another experiment as a bedroom. The only other difference between the two rooms was the glazing of the window. In one room a standard three-pane window (2+1) with 4 mm clear glass was used, in the other a super-insulated four-pane window (3+1) with two silver-based low-emittance coatings. The results showed that people were clearly able to distinguish between the two windows. The room with the four-pane window felt more enclosed, and the daylight felt less strong and clear. The four-pane window also affected colour perception, making the colours of the room and of the view look more subdued or more drab. Spectral measurements revealed that the four-pane window transmitted a relatively higher percentage of the green part of the spectrum. The results agree with what might be expected given the lower transmittance and different spectral distribution of the four-pane window. It is questioned how far one should go in reducing the daylight transmittance of windows.