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  1.  
    Time marches on, and tempered evacuated glazing (from China?) is now apparently available in Canada:

    http://vacuumglass.ca/
    • CommentAuthorringi
    • CommentTimeJun 15th 2017
     
    These come into their own if listed building control will not let you change the windows, hence stopping you using normal double glazing.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 15th 2017
     
    Wow! the void gap is only 0.2mm, overall unit thickness 0.44inch. 'normal vacuum glass' 0.62w/m2k, other options a bit better.

    First, this revolutionises glazing for Listed Buildings - near-PH with no effort!
    Second, for real PHs, this plus an extra single glass should be good enough; phenomenal Uvalues with multiple.
    •  
      CommentAuthordjh
    • CommentTimeJun 15th 2017 edited
     
    https://www.pilkington.com/en-gb/uk/products/product-categories/thermal-insulation/pilkington-spacia

    "Proven solution; installed successfully in the UK and used in Japan for over a decade"

    edit: "samples are available however, since they are rather expensive, we ask for details about your project"
  2.  
    NSG Spacia is not (or was not) available tempered.

    Tempered evacuated glazing has many more potential uses.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 15th 2017
     
    Bizarre - the Pilks product gives centre-pane U = 1.1, and compares it to 4/16/4 U = 1.7 - which sounds like the old days (it's only K-glass not soft-coat).
    Anyway, 1.1 centre-pane is not impressive - esp compared to the Canadian one's 0.62.
  3.  
    I think they might have a lower temperature offgassing process. The old high-temperature process would start to anneal the glass and destroy soft low-e coatings.

    Either that and/or they are using glass with a high critical temperature and heat resistant soft coatings.

    It's possible they might have a better spacer material. It doesn't appear to say.
    •  
      CommentAuthordjh
    • CommentTimeJun 15th 2017
     
    Tom, where are you reading the 0.62?
  4.  
    I acquired a sample of this vacuum glass when I was investigating slim-line double glazing in 2012. The sides/edges are made from glass so very unlikely to 'off-gas', spacers are visible in the wrong light. There is a slightly unsightly plug on each pane which is used to extract the air to make the vacuum. Overall I feel it is a very well engineered product. Its shortcomings seems to be 1) cost £500/m2 (2012) 2) its made in Japan and then shipped by sea, so you need to be patient, and make sure you don't make a mistake over sizing.
    I do however feel it might be more reliable in the long term than other (UK made) slim line double glazing products which rely on expensive inert gases, and appear to use sealant for edge spacers, which I suspect will off-gas over time.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 16th 2017
     
    Posted By: djhwhere are you reading the 0.62?
    Converted it from Murican.
  5.  
    Why would there be a difference in the U-value of the Japanese product compared with the Pilkinton product if they're both Vacuum Glass?
  6.  
    The Japanese product is the Pilkington product. The new one is Chinese.

    I notice that the figures they're quoting are for 11mm overall glass. Since the glass is thicker, that might mean fewer spacers could be used as the glass would bend less under atmospheric pressure. A fairer comparison would be between the 6mm versions.
    •  
      CommentAuthorfostertom
    • CommentTimeJun 17th 2017 edited
     
    yeah, the older Pilks product that ActivePassive is talking about is 6.2mm thick, centre U=1.1 or 0.9, prob uses old fashioned hard-coat K-glass (Pilks, like Dunlop and other UK household names, now a Japanese co).

    The new Chinese one is 11mm thick, basic version centre U=0.62
    and amazingly down to 0.23 for 18mm thick laminated, quite opaqeuish solar control glass - prob uses soft-coat glass
    The ability to use soft-coat maybe for heat-process reasons that passivhausfan mentions 2 above.
  7.  
    I emailed Icesun (and sent them the URL of this discussion, so they might possibly weigh in), to ask what the U-value of the 6mm product was.

    Somewhat confusingly they said that the thinnest available was 8.4mm, but they might have meant that the thinnest available tempered was 8.4mm, which would make sense as I asked specifically about tempered versions, and 3mm tempered glass is rather rare in any case.

    This is the performance they quoted me in metric units for the tempered 8.4mm version that seems most useful to me in a UK climate:

    # 3 Central U Value 0.5 W/m2.K, VT 62%, SHGC 0.48

    That seems better than what's stated on their website in American units. I am not sure why? Maybe they used American climate modelling conventions for the American units and some other conventions for the metric ones? I don't know.

    They can do a higher SHGC, but only by omitting the low-e coating, which strikes me as pointless.

    I really think if this turns out to be a reliable product, the architectural possibilities are very exciting, especially in heritage and traditional domestic architecture applications, although it would require modifications to the design of sashes and casements to take full advantage because of the high edge conduction that all evacuated glazing suffers from.

    You really need the edge to be lost in insulation so that the path for heat transfer is lengthened.
    •  
      CommentAuthordjh
    • CommentTimeJun 17th 2017
     
    Posted By: passivhausfanThey can do a higher SHGC

    In the figures I saw quoted earlier for vacuum glazing the SHGC was notably high, so I'm surprised that this is so low, and especially surprised that it is below the PH minimum allowed?

    You really need the edge to be lost in insulation so that the path for heat transfer is lengthened.

    Agreed but that will need some extra careful design if the glazing is to be replaceable.
  8.  
    Chinese vacuum glass manufacturer:
    http://landglass.en.made-in-china.com/product/kSvJcgnCsfRm/China-Landvac-China-Supplier-Sound-Insulation-Vacuum-Gorilla-Glass-for-Car-Front-Glass.html
    U value of 0.48, or 0.42 for the triple glazed version, more here: http://www.landglass.net/News/Group-News/Safety-Vacuum-Glass-Sets-New-S.html
    possibly the same one as in the http://vacuumglass.ca/ reference above?
    •  
      CommentAuthordjh
    • CommentTimeJun 19th 2017
     
    Exactly the sort of stuff I'd want to see a PHI certificate for before I touched it. What exactly is "Sound Insulation Vacuum Gorilla Glass For Car Front Glass"?
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