Are you in an extreme weather location - snow, wind, bushfire? Reducing the number of windows is a great help, as windows are the biggest points of leakage. But if you are in an area where windows are open most of the time then no. If you are doing these windows, also make sure you have flanges on all pipes going through walls, underfloor insulation, as well as walls and roof. Manufacturers should be able to give you some data that you can correlate with your house size, windows, but really it should be part of a whole house solution.
Thank you. We’re in Tassie. The area is cold & windy in winter but not extreme. We’ll definitely have insulation wherever possible! Double glazed windows are mandatory though we’ve not had those in the past and we haven’t been cold. Our friends tell us we should go with thermally broken but others say the extra cost may not really be worth it. Thanks for your response.
I would say if you can afford them go for it. I would save money on evaluating window size. There is a trend towards oversized windows and windows to floor. Are they really necessary?
I'm sure I've seen graphs comparing the effectiveness of non thermally broken aluminium, thermally broken aluminium, and UPVC. I'm not sure but as I recall UPVC works out mid-range cost-wise. Worth finding info that quantifies the comparison.
Thanks Kate. We think we’ve been ‘sensible’ with the windows. Some sliding doors but the windows have space under them for a bookshelf or desk (for example) or a chair in front of them.
Aluminium has a thermal conductivity of 239 W/m·K. For comparison, wood has a thermal conductivity of 0.15 W/m·K, uPVC 0.19.
All this means is that aluminium is an extremely poor insulator.
I'd only ever consider it as a window frame options in the mildest of climates, like coastal Sydney, or Port Macquarie.
For any climate that requires double glazing, unbroken aluminium frames are a very bad idea. They'll introduce lots of cold into the home in winter. Along with lots of condensation on the frame, which can lead to mould. They'll transport heat into the home in summer time.
So yes, if aluminium frames are being used for double glazing, it's imperative that the frames are 'thermally broken'.
The other options are uPVC or timber frames. uPVC is often comparable in price to thermally broken frames. For some manufacturers thermally broken frames cost more, for others uPVC frames cost more. As shown above, uPVC is a reasonable insulator. UV stabilisers are added, so the frames should last reasonably well. But PVC is the most environmentally destructive of all plastics. Luckily it is now possible to recycle uPVC, what proportion is recycled is anybody's guess.
Timber is the most sustainable choice. Locking carbon into the structure of the home, while other options emit carbon during their manufacture. As shown above, timber is a reasonably good insulator. Timber frames are the most expensive option & most will require ongoing maintenance.
Kate
Dallas GlasbyOriginal Author
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