Treats report investigating results of door opening in terms of energy loss and changes to indoor climate. In 3 sections. Treats: 1) general regulations and manufacturing standards and relevant swedish building regulations concerning airtightness, thermal insulation and functional aspects. 2) Flow of air under different conditions such as pressure differences caused by variations in temperatures and wind. 3) Describes laboratory experiments using 1:10 scale fluid model. Concludes by explaining how porches and similar constructions can reduce amount of air exchange and improve indoor climate with resultant decrease in draughts at floor level.