Choosing a window is a lot more difficult than you might think; just go to a store and try to decipher the experts’ jargon. These days, there’s a whole maze of window technology and standards to figure out.
For your construction or renovation project to succeed, it’s important you’re familiar with window terminology and standards. This buyer’s guide will help you understand window manufacturing standards and the vocabulary used by window experts so can make a truly informed choice.




A unit assembly of stiles and rails for holding the glass (solid sheet, tempered, laminated, or several panes) that moves when the window opens.


A component of an operable (opening) window, providing a seal between the window frame and sash.


The mouldings that surround the window and cover the frame.


The horizontal and vertical portions that surround the sash and on which it is hung.

Spacer bars

Spacers appear around the perimeter of the sealed glazing unit to provide uniform separation between the panes of glass in multi-paned windows; they incorporate a dessicant that absorbs moisture from the trapped air in the space between the glass, preventing condensation.

Brick moulding

The outside casing around windows to cover jambs and through which nails are driven to install the window.


The “hung” mobile panel of a window that opens and closes by rotating on hinges or flexible joints; windows may be single-hung or double-hung.


The glass panes in the sash of a window.


The performance of windows sold in Canada is defined in a Canadian Standards Association (CSA) standard called CSA A440. The A440 Standard sets the type of materials that are to be used (from glass to cladding) and defines minimum performance levels for windows, tested by means of a performance evaluation system. The characteristics evaluated include airtightness (A1 to A3, A3 being the highest rating) watertightness (B1 to B7) and wind resistance (C1 to C5). The National Building Code sets the minimum acceptable rating for each of these characteristics in residential renovation. It is however recommended to opt for A3, B3 and C3 ratings and for even higher ratings in harsher climates. For further details concerning the tests carried out on different window models, go to the CSA website at

Since these tests are expensive for manufacturers, many do not have their products tested. Although many untested products would probably receive a favourable rating, it is advisable to choose products that have been tested.