Due to the high air tightness of windows and external doors as required in the thermal insulation regulations, this standard does not give any information on constructions with shafts above roofs and air supply from adjacent rooms although these constructions were applied frequently and with good results in the past. Since the problem of ventilation of dwellings requires general regulation, there is a tendency towards restandardization of constructions with shafts roofs and air supply from adjacent roofs if it can be assured that the air supply necessary for inside bathrooms and WCs can be taken from the dwelling.