To reduce resource use, choose high-performance windows with frames made of wood, aluminum, fibreglass or a mixture of these materials. Among the different types of windows, the most airtight are casement windows, where all four sides of the sash leave the frame when the window is opened using a mechanism that holds the sash.

Our recommendations :

1. Casement (or “crank”) windows offer the best airtightness because of their double compressed weatherstripping, which can be replaced if it breaks. Hanging and sliding windows have to slide along the frame, which prevents the use of such high-performance weatherstripping. The airtightness of newer window models has improved remarkably, and adding a plastic film in winter allows them to achieve efficiency similar to that of a casement window.
2. Pay special attention to basement windows: The window well should be below the level of the window, filled with gravel and equipped with a drain connected to the French drain, to allow water to drain quickly.
3. Windows are made of many different kinds of materials. Although each has its own advantages and disadvantages, the first factor to consider is its durability, to extend the lifetime of the product:
   • Aluminum is very durable, requires little maintenance and offers the best rigidity, which means the windows can be bigger. It is highly heat conductive, however, so the structure of the sash must be well insulated, with polyurethane foam, for example.
   • Fibreglass is very durable and rigid, requires little maintenance and offers good energy efficiency, thanks to sashes injected with polyurethane foam. It can also be covered with aluminum on the outside and wood on the inside, but very few models offer this option.
   • Wood is warm, durable, and rigid, and it provides good insulation, but it demands regular upkeep to avoid mildew and maintain its appearance. To avoid this problem, the outside of the frame can be covered with PVC or aluminum. The covering must be perfectly leaktight to prevent the wood from rotting.
   • Although PVC windows are affordable, easy to maintain and offer good insulation, they do have some shortcomings. Poor quality PVC can emit chlorine into the air in the home and it degrades under UV rays. It is important to choose high-quality PVC with a thicker profile. PVC is also less solid than metal: the frames are often wider, reducing the glass surface. The production and disposal of PVC can release toxic pollutants into the environment as well.

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