chapter  3
57 Pages


The main purpose of a window is to allow natural light to enter a building yet still exclude wind, rain, and snow. Windows are also a means of providing ventilation when the glazed area is made to open and trickle vent (Fig. 3.64) within their frame. An openable ‘light’ (a singleglazed unit of a window) is called a ‘casement’ or ‘sash’ – hence the term ‘casement window’ or ‘sash window’.