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Green Building Bible, Fourth Edition
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  1.  
    I'm looking to replace a bunch of double-glazed units in some PVC windows - and just wondering if anyone can recommend any suppliers on basis of cost and/or quality?

    One thing I'm interested in is whether any of them offer a meaningful (ie, there is some chance of actually being able to claim on it) warranty. This would be assuming I do the installation myself.

    Thanks!
    • CommentAuthorRobL
    • CommentTimeJul 2nd 2021
     
    These guys offer some limited range on their website:
    https://www.modernupvcwindows.co.uk/
    But Pilkington K only, whilst Planitherm are slightly lower U value. Beware it's not clear if the 2G are warm edge, the 3G state they are.
    I've not bought any DG sealed units only from them, but I have bought other stuff (everything 3G warm edge), and they rectify any mistakes they make quickly.

    I replaced all of ours some time back, bought from a supplier in Peterborough, they're not trading now. The pvc units are 30 years old now, DG all planitherm. Measure the original DG units 2 or 3 times, and be sure about which units must be toughened. Measuring took me longer than replacing. Specify Argon fill and warm edge, suppliers still sometimes use aluminium !
    • CommentAuthorMike1
    • CommentTimeJul 2nd 2021 edited
     
    GGF members offer 10-year insurance backed warranties. You'll need to read the details and / or consult a lawyer to decide what they're worth.
    https://www.myglazing.com/about-ggf/your-guarantees/
  2.  
    Posted By: RobLThese guys offer some limited range on their website:
    https://www.modernupvcwindows.co.uk/" rel="nofollow" >https://www.modernupvcwindows.co.uk/
    But Pilkington K only, whilst Planitherm are slightly lower U value. Beware it's not clear if the 2G are warm edge, the 3G state they are.
    I've not bought any DG sealed units only from them, but I have bought other stuff (everything 3G warm edge), and they rectify any mistakes they make quickly.

    I replaced all of ours some time back, bought from a supplier in Peterborough, they're not trading now. The pvc units are 30 years old now, DG all planitherm. Measure the original DG units 2 or 3 times, and be sure about which units must be toughened. Measuring took me longer than replacing. Specify Argon fill and warm edge, suppliers still sometimes use aluminium !


    Thanks. Yes I will be going for warm edge and argon fill.

    As far as I can make out, the difference between Pilkington K and Planitherm is fairly marginal.

    Did you take all the old units out to measure them, or did you manage to work it out while they were still in the frames?
  3.  
    Posted By: Mike1GGF members offer 10-year insurance backed warranties. You'll need to read the details and / or consult a lawyer to decide what they're worth.
    https://www.myglazing.com/about-ggf/your-guarantees/" rel="nofollow" >https://www.myglazing.com/about-ggf/your-guarantees/


    Thanks - have used the GGF website to find a member near me, and I'll see how their quote looks.
    • CommentAuthorlineweight
    • CommentTimeJul 2nd 2021 edited
     
    So far this is the best website I've found that gives you an instant price -

    Sealedunitsonline.co.uk
    • CommentAuthorRobL
    • CommentTimeJul 2nd 2021
     
    I took all the plastic beads off one window, and discovered that for my windows the "hole for the DG" was identical to the visible beading. The DG had to actually come out to measure the thickness itself. After that I didn't need to open any more up, just measured bead-bead and take 10mm off each X and Y size. This was true for all windows that were identical frame manufacturer. Then measure them all again! How many times on grand designs do they get the glass wrong ?
    To get the beads off I used a kitchen knife (!), then a plastering thing, then some other thicker bits of clean metal, two at a time twisting them until the bead popped out. Don't use anything small like a screwdriver, it will mark the beads.
    I think Pilk K is U=1.3, Planitherm total+ is generally U=1.1, for "standard" air gaps of DG upvc. Alu edge would generally swamp that sort of difference, but worth having, it's no cost diff as I understand it.
  4.  
    My units are (I think) 18mm thick.

    For that, the u-values I am being given are:

    Pilkington K: U=1.8
    Pilkington "Soft coat" (??): 1.5
    Planitherm: U=1.4

    One supplier has offered me Krypton instead of Argon fill, to give U=1.1 ... but at about 3x the price.
    • CommentAuthorRobL
    • CommentTimeJul 2nd 2021
     
    Did you take a DG out to measure the thickness? 18mm upvc is unusual, that would be 4/10/4 I assume.

    Are the 3 argon options the same price then? How much is that? I remember ~10 years ago paying £60/m^2 + VAT + ~£150 delivery for about 20m^2 of 4/16/4 DG warm edge argon fill planitherm+ by the way.
  5.  
    I've not taken one out to measure yet - 18mm might not be quite right.

    The prices for the argon ones vary as they are not all from the same supplier.

    The planitherm quote seems to be coming out around £75/m^2 plus VAT (for non-toughened).

    I've only got initial prices right now and need to go back to pin down some spec details before making direct comparisons.
  6.  
    Posted By: RobLDid you take a DG out to measure the thickness? 18mm upvc is unusual, that would be 4/10/4 I assume.

    Are the 3 argon options the same price then? How much is that? I remember ~10 years ago paying £60/m^2 + VAT + ~£150 delivery for about 20m^2 of 4/16/4 DG warm edge argon fill planitherm+ by the way.


    Having partially dismantled a window, I've measured the DG unit - I totally got my 18mm estimate wrong as the overall thickness measures somewhere between 27 and 28mm so am assuming they are 28mm (4+20+4).

    This changes the U-value a little (but not the cost), so an Argon filled planitherm unit is being quoted as U=1.0.

    (It appears to be the case that a spacer gap of 14mm gives the best U-value with no improvement seen with anything wider than that)
    •  
      CommentAuthordjh
    • CommentTimeJul 4th 2021
     
    From memory I thought the optimum for argon was 16 mm, and for krypton 12 mm. It may be that the overall depth of 28 mm is designed to allow for 6+16+6 where needed and it's convenient to use the same overall size even with 4 mm glazing?
    • CommentAuthorRobL
    • CommentTimeJul 4th 2021
     
    I just checked with Pilkington Spectrum (free, try it), it confirms djh - with Argon and the (Pilkington) softcoat the optimum gap is a nonstandard 15mm. Increasing to 20mm is ever so slightly worse, but still a huge improvement over the original glass I expect.
    You could also fit 4:8:4:8:4 with Krypton fill and get U=0.6, likely at twice the cost. Caution though, as it would make the windows 50% heavier, so any openers might not work right - don't do this for large opening windows. We had 3 smaller (opening) windows that were 4:20:4 (originally Alu spacer!, air fill, glass with no coatings), and I swapped them to 3G krypton U=0.6 as I'm suggesting, with no issues. All our other windows were 4:16:4 I think, and some were very heavy anyway without doing that - so I'm glad I didn't have that quandary!

    On our south facing windows, I got Planitherm Total+ with SGG Diamant, which marginally increases solar gain. There's all sorts of options though.

    If the magic gasses came out, your DG becomes U=1.3, and the 3G becomes U=1.2.
    • CommentAuthorjms452
    • CommentTimeJul 4th 2021
     
    I asked our three local window fitters if they could do low u-value replacement glass and one of them surprised me and knew what they were talking about.

    They measured up, swapped got rid of the waste and I get the warranty.
    The also fixed some drafts with the uPVC french doors while they were here.
    •  
      CommentAuthordjh
    • CommentTimeJul 4th 2021
     
    Posted By: RobLOn our south facing windows, I got Planitherm Total+ with SGG Diamant, which marginally increases solar gain. There's all sorts of options though.

    Yes, we have it relatively easy here, where all we have to think about is the cold weather heat loss, plus make sure the backstop of at least 50% visible light transmission is met. Life must be much more exciting where you have to worry about summer solar gain and suchlike. :)
  7.  
    Posted By: RobLI just checked with Pilkington Spectrum (free, try it), it confirms djh - with Argon and the (Pilkington) softcoat the optimum gap is a nonstandard 15mm. Increasing to 20mm is ever so slightly worse, but still a huge improvement over the original glass I expect.
    You could also fit 4:8:4:8:4 with Krypton fill and get U=0.6, likely at twice the cost. Caution though, as it would make the windows 50% heavier, so any openers might not work right - don't do this for large opening windows. We had 3 smaller (opening) windows that were 4:20:4 (originally Alu spacer!, air fill, glass with no coatings), and I swapped them to 3G krypton U=0.6 as I'm suggesting, with no issues. All our other windows were 4:16:4 I think, and some were very heavy anyway without doing that - so I'm glad I didn't have that quandary!

    On our south facing windows, I got Planitherm Total+ with SGG Diamant, which marginally increases solar gain. There's all sorts of options though.

    If the magic gasses came out, your DG becomes U=1.3, and the 3G becomes U=1.2.


    Thanks.

    I've thought about putting triple in but would be worried about the weight. I suppose I could put triple in non-opening panels only.

    But probably my feeling is that it wouldn't really be worth it for double the price. Reglazing the old PVC windows is sort-of a stop-gap solution. Really I'd like to replace the windows with something better overall - but that would be pretty disruptive for various reasons. If I'm still here in 10 or 20 years, that might happen.

    It'll also depend a bit on how long the PVC frames last - which seems to be a bit of an unknown. It seems to me that PVC frames can probably last quite a lot longer than is usually assumed... many problems with them are actually to do with hinges and so forth, which can be quite easily and cheaply replaced.

    So in other words, I'm not sure how much longer these windows will live - their end will be determined by me getting round to sorting them out properly, or some kind of point of deterioration of the PVC, both of which are on an unknown timescale.

    So for that reason it feels worth it to make a significant difference to U-value by replacing with new DG units (several of the existing have failed and misted anyway) but probably not increasing the cost by a large amount to improve the U-value further.

    The price I've been given already for krypton DG was 3x the argon price - so I wonder how 3G would come out.
  8.  
    I'm just refining the spec for my order.

    By default it'll be 4mm clear - 20mm argon - 4mm "Planitherm One".

    But there's an option to swap the outer pane for 6.8mm laminate which would then make it match what Planitherm call their "Comfort Plus" spec here:

    https://www.planitherm.com/media/5598/422757-sgg-planitherm-a4-info-leaflet.pdf

    The main attraction of this is the claimed improved acoustic insulation - but of course it comes at additional cost.

    Does anyone have experience of replacing existing units with this type of spec and noticing a significant difference? The room concerned does face onto a street with traffic. But of course, it'll only work when windows are shut.
    • CommentAuthorMike1
    • CommentTimeJul 7th 2021 edited
     
    FWIW I''m about to order 6.8mm laminate for some new windows, mainly for the additional acoustic insulation, but also because the most common plastic films (PVB & SGP) used in laminated glass also cut out almost all UV light, which prevents fading of fabrics and furnishings. At ground level they also offer additional protection against intruders and stray footballs - so a good idea to have the laminated glass on the external face, unless it's required to be on the internal face for safety reasons. In fact, I've always ordered one laminated pane whenever I've ordered double glazing, as at least one of those factors has always applied.

    Of course if you have trickle vents, then the acoustics of the windows will be compromised and upgrading the glass (for that reason) may make little difference. The quality of the frame, and sealing between the frame and wall, also have some influence.
    • CommentAuthorMike1
    • CommentTimeJul 7th 2021 edited
     
    Posted By: lineweightIt seems to me that PVC frames can probably last quite a lot longer than is usually assumed.

    It's very dependent on quality, location, and how they're treated. See my post here:
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16691&page=2#Comment_285434
  9.  
    Posted By: Mike1FWIW I''m about to order 6.8mm laminate for some new windows, mainly for the additional acoustic insulation, but also because the most common plastic films (PVB & SGP) used in laminated glass also cut out almost all UV light, which prevents fading of fabrics and furnishings. At ground level they also offer additional protection against intruders and stray footballs - so a good idea to have the laminated glass on the external face, unless it's required to be on the internal face for safety reasons. In fact, I've always ordered one laminated pane whenever I've ordered double glazing, as at least one of those factors has always applied.

    Of course if you have trickle vents, then the acoustics of the windows will be compromised and upgrading the glass (for that reason) may make little difference. The quality of the frame, and sealing between the frame and wall, also have some influence.


    Yes - the UV blocking is an additional benefit.

    Do you have experience of replacing old DG without laminate, with new DG that does?

    I'm finding it hard to judge whether the improvement in sound insulation will be significant or marginal.
  10.  
    Posted By: Mike1
    Posted By: lineweightIt seems to me that PVC frames can probably last quite a lot longer than is usually assumed.

    It's very dependent on quality, location, and how they're treated. See my post here:
    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16691&page=2#Comment_285434


    Yes, you mention a 20-30yr life expectancy there - I don't know exactly how old mine are but I think it must be at least 20 years. I don't see anything obvious starting to go wrong with the plastic - and the fact that I seem to be able to pop the glazing beads in and out OK I am taking as an indication that it's not really going brittle.

    All the problems with mine have been to do with hinges getting bent (I'd thought frames were warping but it was just the damaged hinges forcing the opening casements to try and shut in a twisted orientation) or failure of the handle mechanisms, or deterioration of the foam tape or the various gasket seals, all of which it's possible to replace (and quite easy to source).

    When I've tried to look into longevity before I've found that there's no clear answers at all. I note that the life expectancy given for PVC windows often seems to be very similar to that given for sealed units - and I wonder if the two tend to get confused with each other.

    I'm no fan at all of the aesthetics of PVC windows and would seldom choose them from new but I think they are commonly ripped out prematurely. It seems that there must be many cases where you can get more benefit spending money on best-possible spec for replacement glazing, than spending an equivalent amount on fully replacing the windows.
    •  
      CommentAuthordjh
    • CommentTimeJul 7th 2021
     
    Posted By: lineweightBy default it'll be 4mm clear - 20mm argon - 4mm "Planitherm One".

    Planitherm One appears to be designed for doors of appliances. Planitherm One T seems to be the product for windows. And the Comfort Plus spec has a 16 mm cavity. I hope it's just typos in your message. Interestingly, St Gobain's website doesn't list a 6.8 mm Stadip Silence but rather a 6.4 mm one.

    I don't really understand either their description of "SGG SGG STADIP SILENCE 8.8mm glass comprises 2 sheets of 4mm SGG PLANICLEAR glass, assembled with 2 acoustic PVB(A) interlayers." Why are there two interlayers between two sheets of glass? And for best acoustics I'd have thought it was preferred to use two different thickness of glass, to reduce resonances?
    • CommentAuthorlineweight
    • CommentTimeJul 7th 2021 edited
     
    Posted By: djh
    Posted By: lineweightBy default it'll be 4mm clear - 20mm argon - 4mm "Planitherm One".

    Planitherm One appears to be designed for doors of appliances. Planitherm One T seems to be the product for windows. And the Comfort Plus spec has a 16 mm cavity. I hope it's just typos in your message. Interestingly, St Gobain's website doesn't list a 6.8 mm Stadip Silence but rather a 6.4 mm one.

    I don't really understand either their description of "SGG SGG STADIP SILENCE 8.8mm glass comprises 2 sheets of 4mm SGG PLANICLEAR glass, assembled with 2 acoustic PVB(A) interlayers." Why are there two interlayers between two sheets of glass? And for best acoustics I'd have thought it was preferred to use two different thickness of glass, to reduce resonances?


    I think it's just shorthand for what is in fact "Planitherm 1 T" when used in an architectural context. See this page for example -

    https://glassolutions.co.uk/en-gb/products/planitherm-one

    I suppose I could question the company who has given me the quote but if they are selling me a DGU with a stated U-value, manufactured to an EN standard and with a warranty on it then I think I'm happy to assume that they are using the right thing. Their own web page -

    https://www.sealedunitsonline.co.uk/regular/planitherm-one.aspx

    refers to the planitherm 1 "range" which I take to include planitherm 1 T.

    The 'comfort plus' spec buildup does indeed have a 16mm cavity - but I need units to fit into existing frames, and a cavity of 20mm is what I end up with in order to maintain the correct overall thickness with two 4mm panes. If I go with the 6.8mm laminated glass, the cavity becomes 18mm. Not exactly the same as the SGG spec but close enough that I'm not going to worry about it altering the characteristics wildly.


    As for the thing with two layers/8.8mm, I can't explain that! There seem to be some inconsistencies on SGG's own page where they refer to 8.8mm at one point and 8.4mm at another.
    • CommentAuthorMike1
    • CommentTimeJul 7th 2021
     
    Multiple interlayers aren't unusual; it may be that one has particular acoustic dampening properties. It is normal that each pane in the double glazed unit should be a different thickness for acoustic purposes - I seem to recall at least a 40% difference in thickness being a rough guide. But Pilkington - and no doubt others - have detailed tables / calculators.
    • CommentAuthorMike1
    • CommentTimeJul 7th 2021 edited
     
    Posted By: lineweightI don't know exactly how old mine are but I think it must be at least 20 years. I don't see anything obvious starting to go wrong with the plastic - and the fact that I seem to be able to pop the glazing beads in and out OK I am taking as an indication that it's not really going brittle.

    All the problems with mine have been to do with hinges getting bent (I'd thought frames were warping but it was just the damaged hinges forcing the opening casements to try and shut in a twisted orientation) or failure of the handle mechanisms, or deterioration of the foam tape or the various gasket seals, all of which it's possible to replace (and quite easy to source).
    That all sounds encouraging!

    If you have windows facing different ways, you might want to check that they all seem as good, as they may have experienced different levels of UV, thermal cycling, etc.

    Posted By: lineweightWhen I've tried to look into longevity before I've found that there's no clear answers at all.
    There are research reports into longevity overall, but the PVC formulation varies between manufacturers, and environmental conditions vary too, so without some destructive analysis your practical tests above are probably a good guide.

    Posted By: lineweightDo you have experience of replacing old DG without laminate, with new DG that does?
    No, only new. But, as mentioned above, Pilkington do have a tables / calculators that will give you some idea of what the difference will be.
    •  
      CommentAuthordjh
    • CommentTimeJul 7th 2021
     
    Posted By: lineweightI suppose I could question the company who has given me the quote but if they are selling me a DGU with a stated U-value, manufactured to an EN standard and with a warranty on it then I think I'm happy to assume that they are using the right thing.

    One thing I learned when specifying windows is to double (or triple :) check everything and make sure every i is dotted and t crossed in exactly the right place.
  11.  
    Posted By: djh
    Posted By: lineweightI suppose I could question the company who has given me the quote but if they are selling me a DGU with a stated U-value, manufactured to an EN standard and with a warranty on it then I think I'm happy to assume that they are using the right thing.

    One thing I learned when specifying windows is to double (or triple :) check everything and make sure every i is dotted and t crossed in exactly the right place.


    Yes, well you made me sufficiently paranoid to check and they confirmed it's the Planitherm 1 T that they use.
    • CommentAuthorrevor
    • CommentTimeJul 7th 2021
     
    Be aware that plants do not grow at all well behind some types of coatings. Important if like many homes plants are put on window cills for more light.

    https://www.pilkington.com/en-gb/uk/news-insights/archived-blogs/is-coated-glass-bad-for-indoor-plants
  12.  
    Posted By: revorBe aware that plants do not grow at all well behind some types of coatings. Important if like many homes plants are put on window cills for more light.

    https://www.pilkington.com/en-gb/uk/news-insights/archived-blogs/is-coated-glass-bad-for-indoor-plants" rel="nofollow" >https://www.pilkington.com/en-gb/uk/news-insights/archived-blogs/is-coated-glass-bad-for-indoor-plants


    This occurred to me - and I looked it up earlier today, whether UV-blocking laminated glass would be bad for plants, but it seems that if anything, it's better for them. Obviously other coatings will have different effects.
  13.  
    By the way for anyone figuring out options for acoustic/noise reducing double glazing, here are some things I've found useful:

    Handy intro to basics:

    https://www.glassonweb.com/article/acoustic-properties-glass-not-so-simple

    The SGG/Planitherm calculator seems to stop giving me acoustic values once I start putting laminated layers in, but the Pilkington Calculator lets you see the effect of various buildups:

    http://spectrum.pilkington.com/Main.aspx

    (Look under Noise control >> Pilkington Optiphon for various laminated thicknesses)

    Playing around with this gave me a Rw of 31 for my existing old units (4mm-20mm-4mm).

    Changing this to 6.8mm laminated-18mm-4mm improved the Rw to 36

    (Changing to regular 6mm-18mm-4mm improved Rw to 34, and changing to 8mm-16mm-4mm improved Rw to 37)

    These numbers are broadly similar to what can be found here:

    https://asset.source.thenbs.com/api/pdf/a85977de-5570-4d35-b9e1-a6aa4e6eff28


    My understanding is that a 3db noise reduction is "perceptible" and a 5db reduction "noticeable". Of course, I have no way of calculating how much any of this is compromised by the window frames, gaskets and so on.

    Interesting that making the outer pane 8mm float glass instead of the 6.8mm laminated actually gives better acoustic performance. Unfortunately this doesn't seem to reduce price though! And would also come with a weight penalty and no UV blocking.
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