Irrespective of the guidelines herein, the final size and location of any window must conform to the building code for any specific area and the Building Act By-law will govern all such decisions.
Windows for Daylight and Sunlight
Windows have one common function-the admission of sunlight and daylight (all the light from the sky including that reflected or diffused through clouds). Uniformity of daylight across an entire room is the objective.
Dark corners and high brightness contrasts are undesirable in any room.
Factors affecting the distribution of daylight within a room are:
The direction which the room faces
The shape and position of the windows in the wall
The type of glass used in the windows
The amount of light reflected by the ceilings, walls, floor, and furnishings
The type of sunlight controls used inside and outside of the house.
To ensure even distribution of the greatest amount of daylight within a room, the following practices are recommended:
Provide glass areas in excess of 20 per cent of the floor area of each room.
This is generaI rule-of-thumb. Most buiIding codes recommend that the glass area be not less than 10 percent, but much more is desirable to meet daylight requirements on cloudy days. On brighter days, the amount of light can be controlled by interior and exterior shading devices.
Place principal window areas toward the north except in warm climates where a southern orientation is favoured in order to limit heat from the sun.
The north sky is considerably brighter than the south sky. A northern exposure permits the maximum amount of daylight and also the greatest amount of solar heat in winter.
Group window openings in the wall to eliminate undesirable contrast in
Provide one large opening on wall instead of several small ones to do away with dark areas between openings.
Use windows in more than one wall for greater admission and better distribution of daylight.
If one large opening is provided instead of several small ones, a more desirable distribution of light is secured. Dark areas between openings are eliminated.
Select the window shape that gives the desired distribution of light within each room. For a broad, shallow distribution of light, use short, wide windows. Tall, narrow windows give a thin, deep distribution of light. Intensity of light is great near the window and then drops off rapidly and smoothly within a short distance.
Place the window as high in the wall as possible to lengthen the depth of light penetration into the room. If possible, place the head of the window close to the ceiling. More sky is visible through the upper parts of the window than the lower; moreover, the overhead sky is brighter than the sky at horizon.
Do not specify corner windows or bay windows as a means to increase the daylight effectiveness of the window. The actual area of glass is greater and more costly than the effective daylight area obtained.
Use the kind of glass which is most suitable for room purposes.
Use clear sheet for unobstructed vision; translucent glass for privacy since it diffuses images. Special types of glass which reduce glare and heat from the sun are available at higher cost. Glass is the most durable and least expensive transparent material for use in windows.
Screen only those parts of the window that open for ventilation.
Full screens on a double hung window can absorb as much as 50 percent of the available daylight half screens absorb only 15 percent.
Finish ceilings and walls (and even the floor) in light colours to take advantage of light distribution made possible by reflection.
Use flat or dull finishes. Furnishings, especially draperies, should also be light in colour.
Mount draperies, curtains, shades and other window hangings above the head of the window and to the side of the window frame in order to free the entire glass area and thus admit the greatest amount of light.
Dark, heavy draperies hung over the sides and top of a window can reduce the available daylight.
The practice of pulling window shades one-fourth or one-half of the way down results in loss of light at the rear of the room where it is most needed.