Due to the fact that loss of heat due to transmission is on the decrease, the loss of heat due to ventilation is becoming more important. Heat recovery units must be put into use to decrease the heat loss due to ventilation. If mechanical ventilation systems are used to create a minimum air change rate, air-tight windows are necessary - but if no ventilation grilles are used they are out of place.
The ventilation of dwellings. Structural basics. Wohnungsluftung. Bauphysikalische Grundlagen.
IKZ-Haustechnik, 1985. Pt 6, p178-181, Pt 8, p26-33 and Deutsche Bauzeitung, 1984, Nr 2, p231-234, 10 figs, 1 tab, 20 refs.