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Canberra Today 12°/15° | Tuesday, April 23, 2024 | Digital Edition | Crossword & Sudoku

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All double-glazed windows are not created equal!

Windows are the weakest point of the home from an insulation point of view, says Michael Drage.

In his latest  “Tips, Traps and a Little Science” column, MICHAEL DRAGE, founder of Reimagined Habitat, Passive House and energy efficient home designers, offers advice on the differing options and costs when it comes to selecting double-glazed windows… 

WINDOWS are the weakest point of the home from an insulation point of view, except where there are big air leakages. 

Michael Drage, founder of Reimagined Habitat.

In the Canberra region, we notice this especially in winter with the “crying windows”, especially if you have gas heating. 

Apart from being a health hazard from a mould point of view, they just leak heat from now through to October.

So what to do? 

Pretty much every person we speak with talks about double glazing, which is great. The glazing can take many shapes and forms, but generally the newer glass panels are good. The problem is the frames.

Aluminium is the fifth most conductive material in the world. So, aluminium frames conduct heat like a superhighway and some research shows that some aluminium, double-glazed windows will not perform much differently than single – all due to the frames.

Alternatives include UPVC – high performance, well priced; or timber – high performance, high priced; or thermally broken aluminium – mid-to-high performance, mid-to-high price.

So what do we mean by thermally broken? Some aluminium frames these days in Australia – and all in Europe – have a synthetic spacer in the middle to stop that superhighway. The bigger the spacer, the better the performance. Non-thermally broken aluminium windows have been banned in Europe for many years now, and most Europeans are aghast at what is still sold here.


Check the U value of the windows. This determines the performance. The lower the U value, the better the performance. Ideally, aim for windows with U values of 2.5 or lower.

  • If in doubt, check out the WERS rating website and play with their tools.
  • Call us and we can work it through with you.


Many window companies will give quotes on the U value of the glass, not the overall window system. Remember the glass is the better performing area, it is all about the frame system.

  • Even if you get high end windows, make sure they are installed correctly with foam sealant around the window frames. It is no use having great windows if there are big gaps around them leaking air/heat.

We import high-end windows from Europe. So if this is of interest, please reach out and we can see what we can do to help.

Thank you to all our readers who contacted me regarding last month’s topic on energy-efficient homes. Keep the questions coming in, we love helping people upgrade or build better homes.

For any questions, comments or queries, email us at or just give me a call on 0419 391282.



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Thank you,

Ian Meikle, editor

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