Aluclad (u value: .83) v. Aluminium (u value: 1.1)

I've narrowed down my window supplier to two manufacturers, one which supplies aluclad (snip), the other aluminium (snip). It will be triple glazed on the north, double glazed on the south. The above u values are for triple; the aluminium double glazed value is 1.3., and I assume the aluclad is lower.

The aluclad supplier is not appearing on the NSAI website, and neither is the aluminium window from that supplier (that supplier's other windows do appear, though). Is this lack of NSAI certification a negative?

Moreover, does the u value matter that much at this level? The aluminium supplier (who also supplies a different aluclad) says it doesn't and that it could impede solar impact if it's too high (although he, too, said to tripleglaze the north aspect). I prefer the sleek look of the aluminium but I'm not sure if the difference in u value is important enough at this level to go with aluclad; could the aluminium still be a better window despite the higher u value?

Which would you choose, and why?

BryanF

What makes people think 'double on the south' is a good idea ?

What is the u-value of both frames (only)?

3G Aluclad all the way. Assuming architecturally you can get the openings/sash sizes you want

Metric Tensor

Ask your DEAP assessor to check - he/she may have used a better U value in order to make your house comply and therefore if you go for one that's not as good now you may need to balance it by putting in more expensive items elsewhere.

I also think it's madness not putting triple glazed everywhere. There's a fairy story going around about losing solar gain by moving to triple glazing and therefore it being "better" to use double glazing on south facing windows. Although this is based on a half correct notion this is complete bullsh1t. You will lose way more heat through the double glazing than the minor extra bit of heat you will get inwards ... which will come in the summer anyway, when you don't need it.

I'm a fan of aluminium myself so aesthetically it could work depending on the house shape and type. I have found though that the thermal breaking provided in some aluminium frames is quite poor so you need to make sure you are getting a good product. Mind you there are lots of rubbish (so-called) aluclad products out there too!

mrsWhippy

I'm going for triple glazed aluclad all over, apart from the doors that are too large for alu or PVC.

Assuming your house is in Ireland, you're going to want to *keep* the heat in for more hours of the year, than you will want to let it in!

Could you not go for triple glazed aluminium if that's the window you prefer?

Metric Tensor

Metric Tensor wrote: »

I'm a fan of aluminium myself so aesthetically it could work depending on the house shape and type. I have found though that the thermal breaking provided in some aluminium frames is quite poor so you need to make sure you are getting a good product. Mind you there are lots of rubbish (so-called) aluclad products out there too!

This is the thing: we are not sure who is doing the reliable aluclad. Our aluclad proposer, according to his (Irish) opposition, used to make great windows but then moved production to Poland and quality allegedly declined. Overall, our aluminium manufacturer/supplier was dismissive of aluclad - even though he also makes aluclad. He contended that much of the alu part is stuck on and won't last, and he was generally dismissive of the u values as the be-all and end-all in assessing a window's quality. He was also generally dismissive of timber being used in windows saying it's not appropriate - which is the first time I've heard that and considering his firm has been making timber windows for decades I was not a little suprised at his saying this (Is there evidence to support that?)

The price between triple glazed alu-clad (average u value .83 for windows/doors for the whole house) and triple glazed aluminium (average U value = 1.1 for windows/doors for the whole house) is the same (I had been led to believe aluclad was more expensive). In money/heating/BER cost terms, how significant is that u value difference? I suppose that's my central question. What figure do we look at/ask for to find if the thermal breaking in the aluminium window/door is good? Is there any advantage which the above aluminium would have over the above aluclad? Lastly, would the weight of triple glazed on an aluminium or aluclad sliding door's roller be too much? (I've been told it would be for a upvc door, but not an aluminium one; is this true) Thanks.

fatty pang

Deleted User wrote: »

Is this lack of NSAI certification a negative?

No. The NSAI WER certificates are fairly useless and only serve a couple of purposes –firstly it provides you with information that should be on the mandatory CE Declaration of Performance and secondly shows up third-rate designers ( any specification including the wording “include additional cost for ‘A’ Rated windows”). This scheme was copied from the UK where it was only ever meant as an aide to the public to provide some very basic performance indicators in an idiot-proof fashion when replacing their windows. Using it as a specification tool for new build is lazy at best and incompetent at worse.
The NSAI scheme does not include doors. But then again many architects’ specifications don’t either merely lumping them in with the windows.

Moreover, does the u value matter that much at this level?

Yes. The window with a u-value of 1.1 is losing about 1/3 more heat than the window with a u-value of 0.83.

could the aluminium still be a better window despite the higher u value?

U-value is only one of many criteria that should be considered.

fatty pang

Deleted User wrote: »

This is the thing: we are not sure who is doing the reliable aluclad.

You’re not the only one...

Overall, our aluminium manufacturer/supplier was dismissive of aluclad - even though he also makes aluclad.

:eek:

He contended that much of the alu part is stuck on and won't last, and he was generally dismissive of the u values as the be-all and end-all in assessing a window's quality. He was also generally dismissive of timber being used in windows saying it's not appropriate - which is the first time I've heard that and considering his firm has been making timber windows for decades I was not a little suprised at his saying this

I’m at a loss as to why you are still talking to somebody that readily admits that what he is selling is rubbish

(Is there evidence to support that?)

Yes – there are poorly made timber windows as there are poorly made aluminium and plastic windows. On the other hand there are timber windows being made that will last and perform well for many decades. I had the pleasure of walking around Amsterdam last weekend and the city centre is full of houses with timber windows - well detailed, well made and well maintained.

Like with any windows it can be very difficult to tell the difference in quality – an awful lot of professionals have the same problem and it’s often a Q/S (who applies as much thought to buying windows as he or she does to buying toilet paper) that effectively makes the decision on what window goes in to buildings. There are certification and accreditation schemes for windows that the larger manufacturers are signed up to. Some of these are opaque in terms of the information provided and run by trade associations so you need to know how to read between the lines. Others such as Agrement Certification provide comprehensive performance testing of the product and components. For one of the most critical components of any building windows and doors are often the least well specified.
Hopefully you have a good architect or architectural technician that you can call on for impartial advice.