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    • CommentAuthorKenny_M
    • CommentTimeApr 4th 2018
     
    Just thinking ahead to new windows on the modern extension to the rear of my 200 year old house. Flat roof insulation issues I have discussed in another post and I'm still thinking through that, CWI is now in, EWI on the extension probable for the future, but in the main area of the extension where we sit most of the time, nearly 50% of the exterior walls are windows/patio door and so glazing choice will have a huge effect on comfort and heat loss in that room.

    Current windows are circa 1989 narrow gap double glazing, and the sealed units have failed, so even modern double glazing would likely make a noticeable difference. I had initially been thinking double, then starting to become convinced that with so much glass in that small area, and seats very close to the windows, that triple might be worthwhile.

    While searching for triple online, I found the local company below offering quadruple glazing. I did a search on this forum and found only one forum post, from a couple of years back, that had quadruple glazing in the title. I wondered what the thinking on here is now around quadruple, is triple enough, is quadruple unproven etc? This company appear to be claiming a u-value of 0.35.

    http://www.envirowindowsanddoors.co.uk/quadruple-glazing/
    •  
      CommentAuthordjh
    • CommentTimeApr 4th 2018
     
    Ask them for an independent test report.
    • CommentAuthortony
    • CommentTimeApr 5th 2018
     
    Fixed could be quad but I would go for 3g if you want more then add gas and films, I would use a European supplier too

    I have done quad once twenty years ago, very good for sound problems but with wise middle space like 200mm in my case
    • CommentAuthorgoodevans
    • CommentTimeApr 5th 2018
     
    Hmmm - now I don't wish to bad mouth - but the text on that page just doesn't read right. It looks like the 0.35/0.4 U value of Quad/Krypton glazing is hypothesised based on the surface temperature of triple/krypton glazing of an in-situ test.

    The external glass temperature seems to have achieved a temperature below the external air temperature - this is possible if the surrounding environment and sky is on average 'colder' than the air temperature (poor choice of phrasing but we are talking black body radiation/absorption here). But there is no information about the environment other than that it is cloudy - the test seems to have been carried out on one warm day with the radiators on in the house/room. It strikes me that there are too many unaccounted variables to have reached the concluded result.

    Triple glazing makes sense only if you have also sorted other issues such as air tightness, MVHR and other losses - Quad glazing will be better still - but the house will be darker due to a thicker and/or deeper frame and less light transmission through the extra glass. On a retro fit I think Quad will be nearly impossible to justify.
    • CommentAuthorKenny_M
    • CommentTimeApr 5th 2018
     
    djh - good advice, will do that.

    Tony - I've heard 'European supplier' mentioned a few times on the forum, could you give some examples? I contacted Janex, who are local and supply Norwegian windows, recently for a quote. Seemed expensive for supply only, and they were not prepared to recommend any installers.

    Goodevans - I agree the information on that site is very convoluted and seems a bit like sales science. They mention 0.35, but don't make it clear whether that is with the argon fill or the hypothesised krypton fill. Elsewhere on the site they say that all their windows are at least 0.8, but on another page they quote their double glazed windows as being around 1.2, so its all a bit messy.

    I am more curious about quad glazing than serious about putting it on my retrofit. I agree that even triple glazing might be difficult to justify in my scenario, but I doubt that there would be an ROI on DG either in my case, and I am thinking more about comfort in one area. I read somewhere, I think it was pulled from the passivehouse site, that one justification for triple glazing is that with a higher internal temperature close to the inner pane, that comfort levels are increased. The size of the sitting area in my extension means that we sit very close the glass, so I was only considering triple there, and good DG elsewhere.
  1.  
    We have triple glazing installed and I find it very comfortable to live with (e.g. no feeling cold when standing next to a window) and very quiet. It gives me a smile every time I see condensation on the outside and not the inside.

    Our windows (Velfac) were a straight 10% more for 3G over 2G.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 5th 2018
     
    Posted By: Kenny_Mcould you give some examples?
    Russell Timbertech, source theirs here and there across Europe - unbeatable value.
    • CommentAuthorKenny_M
    • CommentTimeApr 5th 2018
     
    Thanks Richard, if only 10% more I would definitely go 3G.


    Thanks Tom. They appear to be just along the road in Glasgow and have a supply and fit service.
    • CommentAuthortony
    • CommentTimeApr 5th 2018
     
    In Austria if you want dg from the big companies you pay 10% more now as 3g has become the volume product with something like a 90% market share.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 6th 2018
     
    Same's true of all the 'Europeans' AFAIK.

    The absolute bargain from Russell is their 4-12-4-12-4 Uw1.1 range - which I personally think is adequate for the price. The same design thickened up to PH grade with 4-16-4-16-4 glass I'm sure costs them no more but is relatively premium price (but still good value compared to the rest).

    A tip - ask Russell to install the 4-16's second airseal into the 4-12 - the groove is already there - but this only works for butt hinges.

    The other co with v similar range and prices is Munster Joinery (all Irish, with UK depots) but personally I find completely baffling to deal with.
  2.  
    Posted By: fostertomThe absolute bargain from Russell is their 4-12-4-12-4 Uw1.1 range - which I personally think is adequate for the price.


    I don't know about Russell windows but is there much of an advantage to having 3g over 2g if the frame isn't insulated?
    •  
      CommentAuthorfostertom
    • CommentTimeApr 7th 2018
     
    Judge by the Uw - the 4-12 range is about 1.1, the 4-16 claims PH, both with the same design of traditional solid timber frame, which I agree is surprising. I think I remember they reckon to make up what the frame loses, by going to town with the glass.
    •  
      CommentAuthordjh
    • CommentTimeApr 7th 2018
     
    Posted By: fostertomJudge by the Uw - the 4-12 range is about 1.1, the 4-16 claims PH, both with the same design of traditional solid timber frame, which I agree is surprising. I think I remember they reckon to make up what the frame loses, by going to town with the glass.

    For PHI certification, the U-value for the window has to be met assuming a standard glazing with Ug of 0.7 so the actual glazing is irrelevant. So if the claim of PH involves the actual glazing, it's probably fake.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 8th 2018
     
    Hmm - I do recognise your concerns, but for 'near PH' I've not let it bother me. In fact have only specified Russell's 'PH' range once, and that because I needed open-in, which the otherwise-cousin narrower-frame range won't. Must say they look v gd.
    • CommentAuthorKenny_M
    • CommentTimeApr 8th 2018
     
    This is all good info, thanks folks.

    Forgive my ignorance but as I have no experience of anything of a higher spec that standard PVC DG I am curious about what it is that these higher end windows bring to the table, over standard PVC types. Is it look, build quality, a combination etc?

    For example I got a price before for a triple glazed timber window 2.9 x 1.2 metres supply only, and it was around £1400 or so inc VAT. Not sure if this is ballpark typical?

    As a comparison PVC framed triple glazed supply only seems to be coming in at around £350.

    These two windows seem to have a similar u value, and correct me if I am wrong but isn't it usually the sealed units that define the life of the window rather than the frame?
    • CommentAuthortony
    • CommentTimeApr 8th 2018
     
    With uPVC life of ironmongery is shorter than the frames

    We have been having troubles at DraughtBusters with failed draught seals, dg units fail too early

    I reckon my 3g windows will last 100 years including the ironmongery.

    Victorian wooden sliding sashes last similar length of time - I see uPVC in skips every week.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 8th 2018
     
    Kenny_M that £1400 quote is fair-to-good, but can be bettered by far from Russell or Munster. PVC's always going to be cheaper again - but the saving is small compared to the BMW-to-Suzuki-cheapo-type difference.
    • CommentAuthorgravelld
    • CommentTimeApr 8th 2018
     
    Saving is small? According to his unrepresentative sample it's a quarter of the price! Put in a decent order and you're talking £1,000s.

    Look into alu clad uPVC if you're worried about uPVC in the sunshine?
    •  
      CommentAuthordjh
    • CommentTimeApr 8th 2018
     
    The problem with PVC is not its behaviour in sunshine. It's everything else. e.g.:

    https://www.greenlivingtips.com/articles/pvc-and-the-environment.html
    •  
      CommentAuthordjh
    • CommentTimeApr 8th 2018
     
    Posted By: tonyWith uPVC life of ironmongery is shorter than the frames

    Eh? You're saying iron rusts away faster than PVC windows become unserviceable? That sounds like a recommendation to buy better ironmongery, except you say yours will last 100 years, so there seems to be no problem with ironmongery?????
    • CommentAuthortony
    • CommentTimeApr 9th 2018
     
    Ironmongery just fails, breaks, snaps, etc
    •  
      CommentAuthorfostertom
    • CommentTimeApr 9th 2018
     
    Posted By: gravelldAccording to his unrepresentative sample it's a quarter of the price!
    From Rus or Mun would have been well less than £1400, esp if it's simple, maybe all-fixed-glass - and I find the £350 figure hard to credit - £100/m2?! the glass alone shd account for more than that?
    • CommentAuthorKenny_M
    • CommentTimeApr 9th 2018
     
    Tom - the £330 quote is correct. It was done through an online company www.modernupvcwindows.co.uk who are a division of Burbage Custom Windows Ltd. I don't know anything about the quality, and I too am surprised by the price as I have bought sealed units only before that cost more per metre, but it is a valid quote.

    Part of my query about the value in upper end double glazing is my understanding that the sealed units have a limited lifespan - ~20 years? Yes, a wooden frame might last 100 years, like my sash and case windows on the front of the house, but the key reason to upgrade a window is the glass, and eventually the gas between the panes leak out and are replaced by air. There is also technology curve - will a 0.7 window be considered obsolete in 20 years?

    Incidentally, the PVC windows here are cheap and yes all the locks, handles and hinges are broken, but the PVC windows in my previous house were 20 years old and not one of them had a problem.

    Not being disagreeable here, and I appreciate all the knowledge being offered, just trying to think through this logically.
    • CommentAuthorTimSmall
    • CommentTimeApr 9th 2018 edited
     
    Poor quality ironmongery can certainly be a problem on min-price PVC windows, but there are suppliers who will use higher spec gear (as standard, or otherwise).

    See previous threads re the better pvc profiles. Off the top of my head, for UK-market specific profiles (cheaper), both Residence 9, and Rehau Total 70 will take up to 44mm units e.g. 4-16-4-16-4, and can usually get you down to a UWindow of about 0.85 W/m²K with argon fill, and mainstream low-e coatings.

    For higher spec, the European market focused profiles like Rehau Geneo are available from some manufacturers (and at least one in the Central Belt I think), these will take thicker units up to 52 mm e.g. 4-18-4-18-4 which is usually optimal for the climate in the UK, and is Passivhaus Institute Certified for the "Geneo PHZ" configuration, and can often get you below 0.75 W/m²K (and will even take quad if you're feeling well-healed and want to head for 0.5 W/m²K), depending on the config. They're also available with an Ali-clad option.

    For the record, I've nothing against timber windows, and have fitted them in the past, and there's certainly a lot of crappy PVC fitted, but that doesn't mean that it's all crap...
    • CommentAuthorTimSmall
    • CommentTimeApr 9th 2018
     
    BTW, it is worth pointing out I think that Krypton fill does have a significantly higher embodied energy than Argon fill (which is reflected in the increased cost). e.g. https://www.sciencedirect.com/science/article/pii/S0196890496001914
    •  
      CommentAuthorfostertom
    • CommentTimeApr 9th 2018 edited
     
    So - amazing but true! No-one else shd bank on that tho.

    Yes all multi-pane units degrade progressively, if they don't actually fail and mist up (shouldn't nowadays). Tony wd agree that in a long-termist world, that's when timber's virtues come through - maintainability in face of the inevitable - units can be replaced but a plastic window liable to be generally knackered by then.

    PassiveHouse standard is consciously set at the sweet point (for your locality) beyond which it's forever pointless (diminishing returns) to go, now or in future - the end of ever-increasing standards. 0.7 (for UK winters) is set to kill downdraught and perception of discomfort, while its remaining loss is supplied 'free' by body heat, cooking etc. So never any point in going lower/quadruple etc in future (that's for now, at points much further north).
    • CommentAuthorTimSmall
    • CommentTimeApr 9th 2018
     
    "Optimum glazing in the regions of Europe considering the embedded energy"

    http://www.passiv.de/downloads/05_report_glazing_embodied_energy.pdf
  3.  
    I have Rehau Geneo reinforced PVC frames which are triple glazed and the frames are insulated. They have Roto hardware which looks pretty robust.
    • CommentAuthorgravelld
    • CommentTimeApr 9th 2018
     
    Posted By: fostertom
    Posted By: gravelldAccording to his unrepresentative sample it's a quarter of the price!
    From Rus or Mun would have been well less than £1400, esp if it's simple, maybe all-fixed-glass - and I find the £350 figure hard to credit - £100/m2?! the glass alone shd account for more than that?
    Except Mun won't deal with him and Rus might get around to making the windows at their convenience ;-)
    • CommentAuthorKenny_M
    • CommentTimeApr 9th 2018
     
    Interesting, thanks all.

    That PDF is an interesting read. If I am reading this correctly it seems that the conclusion is that triple is best for all of Europe, solar gain optimised for South facing, and U value optimised for North, which of course makes sense.

    If I am reading figure 5 correctly though, it seems to suggest that double glazing is sufficient for comfort in most of the UK, although I am just at the bottom edge of the green triple glazing box.

    Also quite surprised by the conclusion that a 0.1 solar gain, is preferable to a 0.1 u value improvement, for pretty much all of Europe, including where I am where the sun has only been a rumour for around the last 8 months!
   
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