u-values on aluminium

middling

I am pricing aluminium windows at the moment for our build.

Company A has told me that their aluminium windows (with thermal gap) have a u-value of 1.8 (compared to their PVC with 1.2). They also have special passive-standard aluminium windows which have a pvc sandwich in the frame, with frame thickness of 90mm. These are more expensive however.

Company B, a much smaller company has told me that their aluminium and PVC windows both have u-values of 1.1 . They didn't give any details of how they get the aluminium window u-values so low, and there is nothing on their website about any fancy technology in their aluminium frames. Am I right to be a bit suspicious of this?!

martinn123

middling wrote: »

I am pricing aluminium windows at the moment for our build.

Company A has told me that their aluminium windows (with thermal gap) have a u-value of 1.8 (compared to their PVC with 1.2). They also have special passive-standard aluminium windows which have a pvc sandwich in the frame, with frame thickness of 90mm. These are more expensive however.

Company B, a much smaller company has told me that their aluminium and PVC windows both have u-values of 1.1 . They didn't give any details of how they get the aluminium window u-values so low, and there is nothing on their website about any fancy technology in their aluminium frames. Am I right to be a bit suspicious of this?!

Perhaps Co. B are confusing the U Value of the glass.
Soft Coat, Low E glass has a U value of 1.1, with Argon Gas, so if they use the same glass in both frames, they might assume, wrongly, that the windows have the same U value.

More Research

middling

Hmm, that's a good point, thanks. You'd think a window company would know the difference though wouldn't you?!

martinn123

middling wrote: »

Hmm, that's a good point, thanks. You'd think a window company would know the difference though wouldn't you?!

They probably do, its the customer who does not know the difference, they are looking out for.;)

middling

Yes, you are right! I will query it and see if it gets me anywhere!

BryanF

middling wrote: »

I am pricing aluminium windows at the moment for our build.

Company A has told me that their aluminium windows (with thermal gap) have a u-value of 1.8 (compared to their PVC with 1.2). They also have special passive-standard aluminium windows which have a pvc sandwich in the frame, with frame thickness of 90mm. These are more expensive however.

Company B, a much smaller company has told me that their aluminium and PVC windows both have u-values of 1.1 . They didn't give any details of how they get the aluminium window u-values so low, and there is nothing on their website about any fancy technology in their aluminium frames. Am I right to be a bit suspicious of this?!

company A - can not be trusted

taken from the current building regulations:

'the replacement of external doors, windows, or rooflights in an existing building.
The average U-value of replacement units
should not exceed the value of 1.6 W/m2K'http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,27316,en.pdf

middling

Hi BryanF,
Sorry only seeing your reply now. Why do you say company A cannot be trusted? Their rep did tell me that he thought the 1.8 u-value was not compatible with building regulations. So he was up front in that respect. Is that what you meant?

On another note, I got back to company B and he admitted that the 1.1 was only for the glass. He said for the full units the pvc would be about 1.3 and the aluminium about 1.5 . Again, I am still suspicious as he seemed to pick those numbers out of the air and I would have thought the 1.5 for aluminium would require some special technology to make them that low...?

Charlie-Bravo

It would be worth while asking for a copy of the certs for the type of window they are proposing. And then look at the NSAI site for more information: Window Energy Performance Scheme.

On the linked webpage there's only one company listed as doing Aluminium and acheiving an A3 cert with 1.53 u-value (if I read the cert correctly?!).

middling

Thanks for that I didn't realise this WEP certification scheme existed. I'd agree, on their list it seems like their is only that one company with the aluminium. But there must be lots of companies not registered with them too - company A that I mentioned before say that they have a window type registered to passive standards but they aren't listed here. (I'm not sure who their registration is with then - presume there is a separate passive-standards body....?)

BryanF

middling wrote: »

Is that what you meant?

I would have thought the 1.5 for aluminium would require some special technology to make them that low...?

yes

&

'thermally broken' aluminium windows are common place/the norm and will achieve 1.5w/m2k

middling

Well, company A has thermally broken aluminium windows and they told me they were 1.8 . I don't know - you can't believe a word out of any of them! Am looking at companies C and D now!