MATERIALS FOR WINDOWS
Windows can be classified into types based on their configuration, or by the material they are made of. Windows are most commonly made of the following materials:
When we say "a window is made of...", we are referring to the frame. The infill is usually glass, but can also be of other transparent materials, such as polycarbonate.
- Aluminium
- Wood
- uPVC and similar plastics
- Steel
- Glass-fibre-reinforced plastic (GFRP)
When we say "a window is made of...", we are referring to the frame. The infill is usually glass, but can also be of other transparent materials, such as polycarbonate.
aluminium windows
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Aluminium is a light, strong material that is excellent for windows. It does not warp, expand or shrink in the presence of moisture, as wood does. It is easy to cut and join together. It can be powder coated or anodized in the factory so that it never needs painting during its lifetime. It is also corrosion resistant.
The one drawback of aluminium is that it conducts heat rapidly, and so causes heat to be lost to the outside in cold climates. The solution for this is to design the window sections with a thermal break, or a layer of a non-conductive material that prevents the flow of heat. Aluminium is made into extrusions at the factory. An extrusion is long piece of aluminium that has the same cross section along its entire length. These can also be called sections in the building trade. An extrusion is made by melting ingots of aluminium, and then pushing the molten metal through a die that gives it the desired cross-section. Key factors in the popularity of aluminium windows are: they are light, which allows easy operation, they are attractively finished, and need little or no maintenance. |
wooden windows
Wood has been the material of choice for windows for many centuries. It is readily available, is easily worked on at site, and is a poor conductor of heat.
Its drawback is that it is expands or shrinks with changes in moisture. This can cause windows to jam or warp. It can also decay in the presence of continuous moisture.
Wood also needs painting or polishing to maintain its appearance.
While wood was abundantly and cheaply available till the middle of the twentieth century, it is now both expensive and difficult to procure high quality, defect free wood sections. It is likely that the use of wood in windows will decrease in the future.
Its drawback is that it is expands or shrinks with changes in moisture. This can cause windows to jam or warp. It can also decay in the presence of continuous moisture.
Wood also needs painting or polishing to maintain its appearance.
While wood was abundantly and cheaply available till the middle of the twentieth century, it is now both expensive and difficult to procure high quality, defect free wood sections. It is likely that the use of wood in windows will decrease in the future.
upvc and similar plastic windows
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Plastics are becoming increasingly common in residential windows. Plastics are light, do not warp, shrink, or decay, and have a reasonably attractive finish that does not need maintenance.
However, plastics are weak compared to aluminium or steel. This is why plastic windows are often reinforced with galvanised steel sections that are hidden within the plastic tubing. Plastics also have a high coefficient of thermal expansion, which can cause problems for windows. Many plastics are also not resistant to UV light, a component of sunlight. Plastics in windows have to be specially formulated to ensure they do not become brittle, crack, or change colour during exposure to sunlight. this is called making materials UV stable. In general, plastic windows are cheaper than aluminium or wood. |
steel windows
Steel is a very strong material, which allows steel windows to have the thinnest possible frames of all materials, maximising views. Unlike aluminium, it is difficult to cut and work, so site work has to be kept to an absolute minimum.
Steel corrodes in the presence of moisture, so it must be galvanised or treated with a high quality moisture resistant painting process. Like aluminium, it is a good conductor of heat, so steel windows must have thermal breaks put in.
Steel corrodes in the presence of moisture, so it must be galvanised or treated with a high quality moisture resistant painting process. Like aluminium, it is a good conductor of heat, so steel windows must have thermal breaks put in.
glass-fibre-reinforced plastic windows (gfrp)
GRFP windows are a recent addition to the range of window solutions. These are made of high quality plastics that are reinforced with glass fibres, giving them high tensile strength and stiffness. As such, they share a mixture of the good qualities of metals (high strength, low weight) and plastics (no warping, no corrosion, good finish).
As they are a new entrant, it remains to be seen how they will perform in the long run.
As they are a new entrant, it remains to be seen how they will perform in the long run.
other materials
Windows can also be made of other metals, such as bronze and stainless steel.
