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Hi Forum,
I have started this topic because I do have serious doubts than Aluminium is suitable for joinery because of it's high thermal conductivity.
As we are all aware that Aluminium is normally used for heat exchangers and other applications where fast heat transfer is required.
How does fast heat transfer match with joinery?
regards
Greetings 'window expert'
Alumin. windows as far as energy efficiency, rate on the lower end of the scale so much so that manuf. now produce 'thermally broken' frames which cut down on the heat transfer to inside the home - Frame 'U' value.
Hi
Aluminium alone in windows has a seriously limited life in the energy equation, every builder will remember - and contributed to - the shift from timber to aluminium over the past 5 years or so. The reasons were obvious - maintenance and cost. Today we have legislation and consumer awareness pushing the energy effiiciency borders to new levels and as
windowexpert says aluminium conducts heat really well (that's why we have aluminium cookware like frying pans
). So under pressure we are looking right now at the shift from a pure aluminium window to PVC and thermal break technologies and as an interim position, timber is making a comeback as a solution to aluminium's poor performance.
Every window manufacturer will shift their focus as they follow this trend. Most manufacturers are already developing the technology.
In the end the consumer will get a better product at a sensible price, it is inevitable.
So if you are thinking aluminium single glazed, think again - your supplier is already working on a better alternative. Don't put old technology into your family home or investment. Nobody cornered the market today in typewriters or sliderules.
Ed
Nah!!! I think we should go with copper joinery
3xb
Aluminium is a great material for windows:
* ultra low maintenance
* clean slim appearance
* can be made any colour or natural anodising
* If anodised, does not have to be recoated EVER
It's also an excellend thermal conductor. Aluminium is used for heatsinks because of this quality. So, use alumimium for your finishing surface, but never link the outside to the inside. That is, use thermally broken aluminium. Then you have the best of everything, unless you like the look of wood (and regular maintenance).
For those that are interested, thermal conductivity values for some materials (all values in W/m.C - the higher the number the more the thermal conductivity):
Aluminium: 220
Brick: 1
Cement: 0.3
Copper: 386
Glass: 1
Gold: 310
Iron: 72
Polystyrene expanded: 0.03
Porcelain: 1
PVC: 0.19
Silver: 429
Steel: 54
Wood: 0.15
So don't make your windows out of solid silver!
Cheers,
Casa
Actually diamond tops the list at 900–2320W/(m*K) so diamond window panes will never be a good idea.
3xb
Yep I can vouch for this.
My place has the old aluminium sliding windows and the ali is freezing and it's actually warmer to touch the glass than the aluminium.
Don't go there.
Steve
The quiet achiever
Stainless steel @ 21 W/m.C
BY the way - you can have timber finish in PVC... we do it. See our website!
J
Do they make stainless steel windows?
Hi Casa
Yes they do - overseas (as always)... and even thermally broken stainless steel.
Looking at your figures I see than aluminium conducts heat: -
7000 times better than polystyrene
1200 times better than PVC
220 times better than glass (and they say that glass is the biggest offender)
10 times better than stainless steel
or inversely has insulation properties that are: -
10% of stainless steel
0.45% of glass or brick
0.09% of PVC
0.014% of polystyrene (e.g. Ecobloc)
Looking at these figures aluminium must be making that hole in the ozone layer all by itself!!
Ed,
Thermal conductivity is only one piece of the puzzle. Fortunatley, there are only three pieces to the puzzle for conductance (we won't even touch radiation and convection heat losses).
Heat loss = Conductivity * surface area / thickness
Therefore although aluminium is 220 times more conductive than glass, it is thicker(which is better) and has a smaller surface area.
If, for example, the aluminium frame surface area is 5% of the glass area and it's thickness is 10 times that of the glass, then the aluminium is 220*0.05/10 = 1.1. That is, you loose as much heat through the aluminium frame as you do through the glass. Very difficult to imporve the glass signifiantly. Changing from single pane to double glazed low emissivity only improves performance by 3 times, but thermally broken aluminium, PVC, wood, etc can give you about 100 times improvement.
I think I've rambles on...
Cheers,
Casa
P.S. Does anyone in Australia sell stainless steel frames or do you know a website.