ABSTRACT
When considering the insulation of a building against heat loss, not only must the walls and roof receive attention, so also must the openings in them and due allowance made for the greater heat loss incurred. Satisfactory ventilation of most rooms located on an outside wall, except in very large and complex buildings, can be achieved by ventilation openings and openable windows, assisted, in some cases, by a certain amount of extract ventilation by mechanical means. The construction around the perimeter of door and window openings can, in the case of walls or enclosing structures containing cavities that must be closed, lead to an increased conductivity and a consequent thermal bridge. In walls that are more than 1.0 m from the boundary, the extent of windows, doors and any other unprotected wall areas depends on the purpose of the building, the distance between the boundary and the side of the building and whether a sprinkler system is fitted.
