I doubt that 4-8-4-8-4 could give 1.0 let alone .71, unless some exceptionally fancy glass coatings. Or unless they're quoting glass-only U, rather than whole-window U. Or even worse, quoting glass pane-centre U rather than whole glass incl the edge spacers. I'd guess 1.4 whole-window (i.e. bare BldgRegs compliance), as it's Al not timber. Exceptionally good value Russell timber 4-12-4-12-4 gives 'typical' 1.1 whole-window, and in more expensive 4-16-4-16-4 so-called 'PH-standard' form, better than that and can be T&T; both are available Al faced externally.

Russell not interested in my project unfortunately

The quote form link above:

"High performance polyamide thermal barrier giving U-Values as low as 1.0 W/m2K when calculated as a domestic CEN Standard window"

Elsewhere I found:

"Very important is how window sizes affect U-Values. Simulations to establish U-Values are typically calculated using a standard window size of 1.23 m x 1.48 m. This is called the CEN standard developed by the European Committee for Standardisation (CEN)."
https://www.doorandwindowexperts.co.uk/47854/the-ultimate-guide-to-window-u-values/

Spoke to supplier - they are adamant that the 28mm is their standard but will check with their glass supplier

What should I really aim to be specifying? Or aiming for?

Thanks

The SMART supplier local to me will only do the SMART 400 in a 36mm 3G setup

What about this supplier:
https://cwgchoices.com/choices-range/windows/alu-clad/tilt-and-turn/

Appears to be the same windows as ALLAN Brothers - or the pictures look the same at least from their website.

Thanks

The range in looking at is the 400, but they said the glass they would provide if I wanted 3G would be the 36mm as they don't do any other...

Okay, any recommended glass suppliers or fabricators of SMART who could do supply only?

I've seen them in person in a showroom and I think this system suits the property not being too thick frames like aluclad and I really don't think spending an extra £10k for slightly better U values adds merit in terms of cost v benefit

They have come back with 3 options:

4-20-4 Argon fill
4-12-4-12-4 Argon fill
3/3-18-4 Argon fill

Not got prices for each option but I'm really thinking of going down the self order route. Can't be that difficult to install frames into a non existent outer skin? Plenty of YouTube videos about

Chat got suggests 20mm argon fill is about optimum fit 2G, unless you go for vacuum or Krypton then you can go narrower.

Maybe I should revisit Russel and see if they are interested now we are ready to proceed on at least 5 windows and a pair of sliding doors.

Do you happen to have the dimensions of their alu-clad range? I'm particularly interested in knowing the power frame widths and what the vertical weights would be between a fixed unit and an opener.

My windows are very basic as 5 are all the same size, 3 with the opening sash on left hand side and 2 with sash on right hand side.

I'd even be tempted to get supply only and get the glass locally, we have very good terms with a local glass firm.

Do they do unglazed? Anything else I should be thinking of to ask Monday?

Ah okay, so 16mm is better than 20mm?

So a 4-16-4 would be better than a 4-20-4? Seems counter, intuitive.

Was meant to say supply only....

Okay so basically I need to be asking for either a 4-16-4 2G or a 4-16-4-16 3G option?

Argon fill, Low E coating

I would like a bit extra sound deadening if possible as we live in an exposed area and the wind can become loud particularly in the Winter months!

I'll make some calls today and see what I can get sorted

Thanks all

I'm assuming that you possibly mentioned sound deadening to your Supplier, which may be why they specified 3/3-18-4 as an option. Laminated glass is generally considered better at sound attenuation.

Posted By: djhTriple glazing, without trickle vents and with good air-sealing (i.e. PH) is quite quiet

So that's only partly about the glass, more I'd say about the frame's air-sealing, and I'd add, any extrusion cavities and/or holes that are open to outside, which can (usually do) have a wind-speed/direction at which they resonate like an organ pipe or whistle. Hard to be sure about all that in advance, but timber windows aren't at such risk, unless they have external aluminium facings.

Might be a better bet than some metals, in a highly corrosive atmosphere. Timber doesn't mind salt, so I'm not sure if I understand why people add potentially corrodible aluminium facings. Shouldn't be any wetter and anyway wetness is no problem to timber providing it can dry out soon. North European joinery softwood is marvellous stuff, unlike the dogends they can sell to UK, and each section consists of laminated thicknesses to equalise any tendency to curl. The 'paint' used isn't 'paint' but pigmented penetrating stain which has long life and can readily be refinished with more of the same, unlike plastic or metal windows. And it's a whole lot cheaper.

Vrogum - excellent make, and Indigo7 - excellent one-man firm, since the present guy, a small developer who had an arrangement to import them direct for his projects, took over from the main UK importer, whose prices were prohibitive. Now they're about 1.5x Russell's price, but Russell are extraordinary cheap, so Indigo7 are otherwise competitive.

I use Russell for 'modern' applications, and accept the premium for Vrogum when it's an older window-style to be matched, as Vrogum are unique in the trade in making their opening sashes glaze-in, while everyone else does glaze-out - as Vrogum do also for their fixed lights. Vrogum's glaze-in sashes present a slim 45o bevel to the outside, which looks pretty much like the putty-line of a traditional cottage window or a posher Georgian/Victorian/till-1920s classic hinged or sliding sash window. To achieve that look, all openings have to have a sash inserted, whether hinged or fixed, as their direct-glazed lights don't look like that. There are other options/features that must also be specified, to make the 'look' work.

Anyway, none of that is relevant to Victorianeco's project, which is 'modern'. Just to say 'yes' to Vrogum.

Also to say that despite previous alerts about 16 being optimum gap, I generally do settle for 12 gap 3G, both with Russell's super-value range (they charge premium for basically the same window but 'PH grade' with 16 gap and double seals) and with Vrogum (with all-opening lights - I have no need of their fixed lights with 8 gap). Even with 12 gap 3G, at U1.1 they beat any aluminium window at U1.4 unless you spend more on exotic fill gas. Alternative to 12 gap 3G, 16 gap 2G is prob almost as good, so I'll be doing that in future, for minimised embodied carbon.

No - I just touched based with the guy (very helpful) from Indigo