Replacing doors and windows with new, airtight models with good thermal insulation is a good way to save energy and reduce greenhouse gases (GHG). Old exterior doors and low-performance windows can account for up to 30% of the heat loss from a home during heating season (Office of energy efficiency). Likewise, inefficient south-facing windows can heat up a home in summer by letting in too much sunlight.

The efficiency of doors and windows is described using the heat transfer rate (U-value) and the energy rating (ER). The lower the U-value, the slower the heat transfer from the hot side to the cold side, and the more efficient the door. The higher the energy rating (ER), the more leakproof the door. It’s important to choose windows suited to the local climate: U-values and ERs are different in different climate zones. You can find out more in store or at the Office of energy efficiency website.

Our recommendations :

1. Choose ENERGY STAR® rated doors: they meet the highest energy efficiency standards, are more airtight and more durable than traditional models. Their energy performance is up to 40% higher than traditional doors thanks to the following features:
   • Double or triple glazing with an insulation layer between the panes. This area is filled in an inert gas (argon or krypton) that is heavier and less conductive than air, and therefore more insulating.
   • Glass covered with an invisible metallic coating, also called low-emissivity or low-E glass.
   • Low-conductivity insulating spacers that reduce energy loss and keep the edges of the window warmer.
   • Insulated door and frame.
2. Choose ENERGY STAR® rated windows: they meet the highest energy efficiency standards, are more airtight and more durable than traditional models. Their energy performance is up to 40% higher than traditional windows thanks to the following features:
   • Double or triple glazing with an insulation layer between the panes. This area is filled in an inert gas (argon or krypton) that is heavier and less conductive than air, and therefore more insulating.
   • Glass covered with an invisible metallic coating, also called low-emissivity or low-E glass.
   • Low-conductivity insulating spacers that reduce energy loss and keep the edges of the window warmer.Insulated sash and frame.
3. Unpleasant overheating in summer is often the result of south-facing windows, but can also be caused by eastern and western exposures, which catch the early morning and late afternoon sun. These windows should be properly shaded by trees, curtains or shade-screens (over the windows) to reduce the need for air-conditioning.
4. When doing an extension or major renovations, putting more windows on the south side rather than the north side allows you to take advantage of passive solar heating. In winter, the noonday sun is far lower than in summer, and it heats rooms by shining into south-facing windows. To let in the most passive solar energy, these windows should not be low-e (low emissivity glass). Since there is no direct light from the north, windows on that side cannot benefit from solar energy, and are therefore one of the thermal weaknesses (insulation gaps) in the house in winter. Windows on this side of the house should be low-e to keep the heat inside. Plan the location of doors and windows carefully to reduce air-conditioning costs in summer and take advantage of the sun as a source of heat in winter.

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