ENERGY STAR qualified windows are a step up in performance over generic aluminium framed double glazing.

Features of ENERGY STAR qualified windows

An ENERGY STAR qualified window will typically have at least one or both of the following features:

  • Double glazing (insulating glass units) and a frame with a plastic or resin thermal break in the centre of the aluminium joinery, or a frame that is made from an insulating material such as uPVC or wood. These are less likely to attract condensation and will lose less heat than windows with standard aluminium frames. Standard aluminium frames often attract condensation in winter even with double glazing.
  • Low-emissivity (low-E) glass as one pane of double glazing, that lets light and heat in, while reflecting escaping heat back into the room.

ENERGY STAR qualified windows may also have:

  • Spacers made of plastic or stainless steel (instead of aluminium) to separate the glass panes to reduce heat loss and condensation at the glass edge.
  • A gas fill (such as argon) between the glass layers that acts as a better insulator than air, reducing any heat loss.

Choosing windows

The following associations provide information to help you choose the right window for your home:

Windows Association of New Zealand (WANZ)

Glass Association of New Zealand (GANZ)

Building Research Association of New Zealand (BRANZ) - Level website


The following companies provide ENERGY STAR qualified windows: