On balance is this good or bad ?

[pstunt]

We have been let down so many times by windows suppliers we are losing the will to live.  

 

I am looking for views on this recent quote from a local installer to us, up in the North East. We have a lot of windows in our build and the attached screenshot is the worst performing U value of the different windows we have been quoted for. This is using one of the relatively newly updated Smart systems ( Alitherm 400 ) and on paper is delivering better U values to when I looked at them last year. I appreciate there are better performing products out there, and we do have a separate ongoing enquiry with a different supplier for a different product ( Mixture of Origin and Internorm ) but we are potentially talking many thousands of pounds difference in price.

 

Given such a large price difference I am trying to reason why  going down the Smart system would be wrong ?

 

 

 

[JohnMo]

Pretty pants for triple glazing.  Let down by the aluminium frame.

 

You can get double glazed that performs as good or better if you are using krypton gas.

[pstunt]

Thanks for the response.

Do you feel that it’s the case of aluminium frames in general which lets it down or this particular frame ? I understand wood or Ali clad are always going to perform better. 
 

I am trying to get my head around why an overall U value of 1.2 is not great ?

 

I get there is better out there but at what cost ? I am trying to weigh up going with “ok” windows with a sizeable cost saving against better performing windows. The consideration being that the possible additional energy expenditure is likely to be way less over the realistic lifetime of the windows.

 

 

[Andehh]

Our aluminium is 1.3 which I'm OK with, would prefer better but it is what it is now. 

[Nick Laslett]

We went with Smart Alitherm Heritage for the Crittal style look. These frames couldn’t take a glass unit thicker than 28mm, so we had to have DGU. This gave us a U-value of 1.3. Smart were still using the older generation polyamide thermal break.
 

Origin and SAS ( Senior Architectual Systems) have newer designs with polyurethane thermal break or Aerogel, these can get to 0.8 u-value. 
 

https://www.seniorarchitectural.co.uk/architectural-systems/pure-window/

 

https://origin-global.com/aluminium-windows/casement-windows

 

https://www.aluminiumtradesupply.co.uk/43667/part-l-2021-how-it-affects-windows-and-doors/#more-43667

 

[pstunt]

Thank you all for the comments

We have got quotes for Origin but it’s even more expensive than our other option  Rationel, which whilst  seems to be a notably higher performing product it’s coming in over 20K more than the updated Alitherm 400.

 

It makes me wonder if that 20k would never be recouped over the life of the windows. Saying that, I have no idea how long windows are realistically expected to last ?

[Adsibob]

20 minutes ago, pstunt said:

Thank you all for the comments

We have got quotes for Origin but it’s even more expensive than our other option  Rationel, which whilst  seems to be a notably higher performing product it’s coming in over 20K more than the updated Alitherm 400.

 

It makes me wonder if that 20k would never be recouped over the life of the windows. Saying that, I have no idea how long windows are realistically expected to last ?

I think you can assume that any half decent window installed now should last 20 years or so. Most windows come with a 10 year warranty (at least mine did) and if they last 10 years, you should easily be able to get 20 with a bit of love and care. If you went for steel windows, 50 years plus is the norm, but then the u values aren’t great on steel.

 

We also wanted crittall style and unfortunately i wasn’t aware of the smart alitherm heritage that @Nick Laslett,  has mentioned above. We went with MetTherm which only have a u value of 1.6 as a standard 2G, although I think with most of ours we specified their higher spec units that have a 1.5 u value. I know this isn’t great, but we are doing okay with them so far. We have not had to turn on the heating yet, and the indoor temp is currently 21 in most of the house with 20.3 by the front door and 21.7 on the top floor. Overnight temp has so far only dropped to 7C, so I’m sure by November we will need at least 2 hours of UFH a night, but we don’t mind that, we like walking shoeless on warm floors, and we like the indoor temp to be in the low temperatures. Ultimately windows are just part of the fabric of the building. An important part, but not the be all and end all, so if spending extra money on windows means you can’t have something equally important like an airtight house and MVHR, or good EWI, or a more premium heating system, then I think targeting stupidly low u values on your windows isn’t worth it. 
 

But then I always knew we wouldn’t get a passive house, however hard we tried as we were starting with a 1930s semi. Obviously if passive or near passive, is important to you, then you probably need to be targeting 3G sub 1.0 windows.

[pstunt]

Appreciate the response @Adsibob very informative and reassuring.

We aren’t aiming for passive standard but rather a reasonable standard. Ours isn’t an easy build as it’s a conversion of a 80 year old stable and we couldn’t rebuild it. It has a lot of windows though. Going to look at the frames tomorrow and quietly hopeful this route may work out as a 20k saving is a big deal. 

[Adsibob]

Have you worked out what the surface area of glazing is relative to the surface area of wall? For us, with the exception of the wall that contains our siding doors, there is much more wall than glazing, as we are semi detached, so hardly no glazing on the side, and the 1930s style was not to have a tonne of glass. But obviously the more glazing you have the more important it is to have lower u values. If money is tight, a compromise option is that you could have cheaper (higher u values) in the bedrooms, where it is actually a bit more beneficial for the temperature to be lower, and lower/dearer u values in your living spaces. For example, in our sliding door, because it’s quite big and an area of vulnerability for the space we spend a lot of time is, we have slightly lower u value, I think 1.3, but I don’t have the spec to hand.

[Andehh]

Just to correct my above point; the U value I quoted above was for the glass alone...due to the Ali frame it is more likely to be 1.5; Frame AND glass.

 

Im pretty pissed off over this, as I didn't bother upgrading/seeking alternatives as asking the U Value of the windows & being told 1.3 meant I chalked it up as an easy win and never gave it a second though, had I known 1.5 I'd have sought better performance in one form or another,

 

I do feel the Window supplier was misleading in quoting a half-truth!!!