What make a window energy-efficient?

What make a window energy-efficient?

October 24, 2016, 08:00 AM

Windows   Materials

What make a window energy-efficient?


What make a window energy-efficient?

It’s easy to say that a window is energy-efficient, but one has to understand why… An energy-efficient window is the sum of its components:

The sealed unit (thermopane)

The sealed glass unit in a window is referred to as the thermopane, which is in itself a combination of a few components.

Low Emissivity glass, called LowE, has a fine metallic coat which prevents heat loss through the windows by reflecting the heat back inside your house during the winter, while heat rays are reflected back outside during the summer.

Inert gas, in our case Argon, is a clear, non-toxic gas used to fill the thermopane. Heavier than air, argon offers greater resistance to heat loss and reduces exterior noise.

Low-conductivity or “warm edge” spacer: it is the element we talked about in this blog that separates glass panes apart but also plays a larger role in creating a thermal break, insulating the edges of the pane and reducing heat transfer.

Low-E windows winter Low-E windows summer

The window frame

The frame material also contributes to the energy efficiency of a window. PVC windows are constructed with many air chambers that make for insulators. Aluminum window frames conduct heat very rapidly and therefore require a thermal break to improve insulation values. The best of both worlds are hybrid windows.


An energy-efficient window must have multiple weatherstrips. Good-quality hardware is also important for tight window sealing.

Casement and awnings windows, which open up towards the exterior of the house, are more efficient in terms of airtightness because the wind will push the sashes against the frame, creating a tighter seal. That being said, innovations in hardware and design mean that good-quality sliding windows can now perform at similar levels.