WINDOW PLANNING

Windows and doors are fundamental elements of the home and can have a huge impact on the look, feel, functionality and overall comfort of your home.

  • Should you choose aluminium or timber?
  • Do you need to open a room up or divide a large space into a smaller one?
  • What type of window or door do you need - double hung, sliding, awning, hinged or bi-fold?
  • What type of glass is best suited for you?
  • Should you consider energy efficiency or sound insulation?
  • Have you considered options such as locks, screens and decorative bars?

Choosing your product

Windows and doors have a very important influence on the design and the structure of the house. Windows and doors, when planned correctly, can make your house work in with your lifestyle and the changing needs of your family. There are many aspects that should be considered when choosing your windows and doors.

From a physical aspect, the main functions of your windows is to bring in natural light and provide ventilation. It is also highly important to control cold air leakage around window openings in winter and heat gain through glass in summer, through careful selection of glass.

Windows also provide an outward view of the world, framing your favourite vista, whilst also helping to maintain the necessary requirements for privacy.

Selection of the types and sizes of windows and their placement will depend on how the windows are to be used. These requirements may be at cross-purposes, for example: the placement and size of a window for maximum daylight may not coincide with placement and size for maximum ventilation or for enjoyment of a view. Careful planning can however help to reach a compromise and return maximum benefits from all requirements.

The final sizes and location of any window must conform to the building code for any specific area and the Building Act By-Law will rule all such decisions.

Ventilation

When planning windows for ventilation, the number, size and placement of windows are all crucial elements to achieve energy efficiency and the overall comfort of your home. The effectiveness in achieving desired ventilation will depend on which windows will open, how far they can be opened and where they are positioned. The difficulty in using a window for both admissions of light and air is that the size and location for the best daylight can often conflict with the size and location that produce the best ventilation.

Some principles of air movement, as applied to houses, are explained below;

  • Air moves because of differences in temperature and differences in pressure. In single storey houses, air movement is predominantly a result of variances in air pressure rather than differences in air temperature. Therefore air pressure should govern the placement of windows in most single storey houses.
  • A high-pressure area is created when air strikes a building.
  • Low-pressure areas are created as the air moves over and around the building.
  • Air flows into a house through openings in the wall against which the wind blows. The wall acts as a dam, causing the air pressure to build up. Air flows out of a house because of the differences in pressure. It moves from high-pressure areas inside the house through openings to areas of lower pressure outside the house.
  • To speed movement of air within a room, the openings through which the air leaves the house should be larger than those through which it enters.
  • Obstacles in the path of moving air cause it to change direction, thus slowing it down, ie: trees, shrubbery or fences on the outside and partitions, walls or furniture on the inside. Because the cooling effect of air in summer depends on its speed, obstructions that slow the movement of air should be kept to a minimum where possible.

The angle at which the air enters and leaves the room is the controlling influence on the pattern of air movement within the house. This angle depends on the location and type of window.

You can use the following recommendations as a guide in selecting windows for ventilation:

  • Provide ventilation openings in excess of 10% of the floor area of a room. This is a general rule of thumb. Most building codes have established minimums of 4-5% of the floor area, but just as large glass areas provide daylight for cloudy days, sufficient ventilation openings can offer relief on warm, humid ones.
  • Position the house and the ventilation openings to take full advantage of prevailing breezes. Do this by determining the high and low-pressure areas as defined by the shape of the house - the walls that the breeze will strike and the walls around which the air moves. Ensure you also allow for changing wind directions.
  • Locate windows so as to effect the best movement of air, a) across the room and b) within the level that occupants sit and stand. Do this by placing windows away from exterior corners and placing double hung, sliding, casement and awning windows in the lower part of the wall since these windows cannot direct the movement of air downward.
  • Plan landscaping, interior partitions and furniture so they do not interfere with air movement. If possible, place the house so that existing buildings and hills do not divert the wind from the house; avoid setting trees, shrubbery and fences in the path of the breeze; plan interior partitions and furnishings so that they do not obstruct air flow within the house.

View

Just as important as the admission of light through them, the view out of the window is one of the most important benefits a window can bring. The outdoor scenery that will be viewed from the house plays a significant role in determining the size of the windows and the placement of the windows.

Sometimes the house is placed on a lot to command a picturesque landscape scene, sometimes the home owner or architect will find it necessary to create a pleasant view to hide a less desirable one, ie: a planted area to hide a car park or a neighbour’s messy yard. Large windows or doors can extend indoor spaces outward, making outdoor living areas an integral part of the house.

Problems in window placement may arise when a house is set on the lot to command a natural view on the east or west since it is difficult to shade the occupants' eyes from the sun early or late in the day. Devices to keep the sun's rays away from the windows may obstruct the view. View windows on the north can be protected from the sun's rays by a roof overhang; the sun does not bother those on the south.

The glare of the sun on an east-west orientation for a view located within the boundaries of a lot is not difficult to control. Fences and tall shrubbery instead of obstructing the view actually define it.

Generally the proportions of the window can be scaled to the view - a horizontal window for a panoramic view, such as a mountain range, a vertical window for a confined view, such as a terrace. In selecting windows to frame any view, it is important to avoid those having obstructions which interfere with the view. The windows should be placed at carefully determined heights so that the sills and the intermediate divisions do not obstruct the line of sight, either for that of tall or short adults.

The following serves as a checklist of good practices:

  • To minimise obstructions in the line of sight use fixed glass except in those areas where ventilation must be provided. Screens are not needed on fixed glass, and therefore eliminate another interference from a standing point of view. Windows having slight divisions are acceptable. A horizontal division more than 100mm thick are not desirable when the division falls in the line of sight. Vertical divisions are not as objectionable as horizontal ones.
  • Determine sill heights on the basis of room use and furniture arrangement.

APPEARANCE

Architectural expression in houses is obtained, to a large degree, by the relationship of window areas to solid wall areas. The number and placement of windows, and even the type of windows can affect the architectural character of the house.

While windows must first be selected, sized and located to satisfy interior requirements, minor adjustments in size and/or location may be necessary to provide an acceptable appearance on the exterior of the house. Windows should be used so that the house gives an appearance of continuity, rather than one of unrelated glass.

Privacy

Use of large glass areas usually requires some controls for privacy, both in the daytime and at night. Obvious controls include drapes, blinds or shutters. Consideration must be given to the size and the placement of these hangings so that they do not cancel the benefits of breeze. The use of louvres or other opaque types of ventilating units, which do not have to be draped, is one solution to this problem of privacy with ventilation. Placing windows high in the wall is another effective means of obtaining privacy, especially in bedrooms.

Heat Loss and Heat Gain

Window areas are a major source of heat loss in winter and heat gain in summer. This heat loss and heat gain can be reduced through correct placement of the house on the lot in relation to the sun, through design of the house as regards the amount of glass area and its location in the walls and through the use of insulating glass, ie: double glazing.

Heat is lost through glass and through cracks around the sash of operating windows. This loss must be taken into consideration in determining the amount of glass to be used in the house, however if insulating windows are used instead of single glazed, larger glass areas can be achieved without impacting on this.

The placement of room heaters below windows, help to eliminate cold droughts since the glass and the air around the windows is warmed. In controlling heat gain, the location of glass areas is more important than the amount of glass. The house should be placed on the lot, and if necessary shaded so that the suns’ rays can be admitted during the winter when solar heat is desirable, but excluded during the hottest months of summer.

DESIGN

In planning for windows, consider the use of large glass areas not only in the living room but also in any room of the house that can benefit from increased daylight, view, or heat gain from the sun. On the other hand, small window areas may serve several purposes well. A bedroom on a western exposure for example may employ a series of short, high windows that supply daylight, provide privacy and yet keep the glass area on this exposure to a minimum so that the rays of the sun are not too unpleasant.

Often a combination of window types is best suited for both interior requirements and exterior appearances. The use of fixed glass with one or more operating window units achieves a functional window that also has a pleasing architectural character.

Such windows permit:

  • The head of the window to be placed high in the wall for daylight.
  • The sill of the opening section of the window to be placed low in the wall - the best location for natural air movement.
  • The middle half of the wall to be left unobstructed for views.


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