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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorGotanewlife
    • CommentTimeNov 10th 2014 edited
    Just had 2 triangular windows installed. One is just a single fixed pane. I can see outside through every single joint. I understand that making odd angles is tricky but even the 90 degree ones have straight through cracks. They will be back tomorrow am to add silicone of about the right colour. The ali profiles are thermally broken.

    Looking at the way these profiles are cut it seems to me that there is no way to avoid every joint being a route for air, without either siliconing each joint or having some sort of gasket (which would be ugly and I have never seen before). And the joints we are talking about are simply butt joints of 2mm + or - aluminium sheet hardly the most effective long lasting solution, especially where the gap itself is as much a 1mm wide.

    I hate silicone unless sandwiched between 2 solid flat surfaces because longevity is measured in months, or a year or 3, whereas window frames should last a bit longer than that! I really need my expectations managed because I trusted these guys and they did deliver against a ferociously tight deadline. So, is it the case that all ali window frames are constructed with silicone at the joints. If so, Uw values would surely be highly dependant upon the skill of the fabricators and subject to deterioration over a short timescale (relative to the life expectancy of the frame). They also fitted the DG units 'dry' up against the ali profile and suggested that it would be better if I added a bead of silicone outside myslef!!!! Would there normally/always be silicone at this joint, or a gasket (such as a narrow version of the one fitted inside)? Very grateful for some timely advice before I blow some fuses, burn some bridges and lose some sleep. Ta.
    • CommentAuthorPaulJ
    • CommentTimeNov 10th 2014
    I would always expect to see a gasket both sides of the glass. The mitres should be very snug fitting. Does not sound great to me.
    • CommentAuthorDarylP
    • CommentTimeNov 10th 2014
    Gnl, are these actaully alu framed 2G windows?
    There should be no gaps in the frames, and the glass should not but up against the alu frame at all.
    Gaskets, glazing tape, or other materials are normally used.

    Sounds v strange...:confused:
    Yes alu framed 2G new. I spec'ed Argon fill, low-e, warm perimeter. Going into an uninsulated solid stone wall so not worth doing more BUT I am working very hard on air-tightness ands my MVHR is already up and running.

    The boss came around and there was no question that they were crxp. He was clear that the glass ought to be against something, I thought he said a gasket/seal but my son, whose Italian is better than mine, wasn't sure that he meant silicone instead - I'll see about that in the morning.

    My primary question though is what about those mitres, surely however tight the operator cuts them, 1 or 2mm thick butt joints in alu cannot be airtight and so silicone is the std for all alu windows; true or not true? Or is it dependant upon the alu profile, or something else.
    • CommentAuthorDarylP
    • CommentTimeNov 10th 2014

    The alu windows I have seen in UK and France have all been machined/cut on jigs, with v close tolerances, practically zero gaps.
    Definately no silicone or other 'retro' works required!
    Have you paid for them yet....?:cry:
    • CommentAuthorGotanewlife
    • CommentTimeNov 10th 2014 edited
    These people have delivered other windows and doors with zero gaps to me before BUT on much closer inspection they all appear to have silicone at the joints, well most of the joints I now find. How can a metal on metal butt joint of the type on a alu window door have a high degree of air-tightness? Maybe they don't. Someone on here will know for sure.....

    Not paid yet but was offered to have the windows taken away and sorted out but since I fitted them with loads of acrylic 'silicone' outside (bound to make a mess of my fresh render) and loads of expanding foam inside, and they don't get weather on them (aside from wind) and can hardly be seen outside or in, I opted for a in-situ remedial work with me helping :wink:
    • CommentAuthorowlman
    • CommentTimeNov 10th 2014 edited
    From my albeit limited experience when specifying aluminium windows, extrusions usually have rigid inserts at the corners which fit into the hollow part of the extrusion. So not really just butt jointed, which would indicate it's just the glass that's holding the thing together. The inserts I've seen had barbs which when hammered in hold each piece of extrusion together.
    The common inserts are 90 degrees and Tees in shape. The problem when speccing awkward angles e.g. triangle windows is ensuring the fabricators have adjustable corner block/inserts.
    Or have I got it wrong and you didn't mean the whole frame?
    • CommentAuthortony
    • CommentTimeNov 10th 2014
    My windows are and I would say that the best one are but typically lots of UK windows are draughty through the frames and even the gasgates and draught strips. We are hopeless, Europe do a lot better.
    Yes the inserts are std and serve to pull the joint together and hold it in place, provide structural integrity etc, usually use an allen key; the alu profiles still only butt up against each other though.

    Tony, are you saying your windows are alu profile, are sealed with silicone and that you believe high spec windows in general in the UK are all sealed this way? That would certainly ease my blood pressure if it is the case.
    • CommentAuthorGotanewlife
    • CommentTimeNov 10th 2014 edited
    OK so PVC windows use basically similar sizes shapes of profile (as far as my issue goes) but the mitre/butt joints are welded, QED alu profiles also need something for these joints too and I found a reference to gaskets being uneconomical in alu framed window mitre/butt joints. So, I guess that means silicone is the only choice - not that i had a choice anyway given my windows have already been made.

    As far as the glass/frame joints are concerned, I am going to insist we use glazing tape (which I happen to have loads of) at the external glass/alu profile joint.....unless he turns up with the correct gasket.

    To be clear, I mean that gaskets at profile joints (butt/mitre) are uneconomical/not used but that gaskets between glass and alu frame are normal/std. Also, a gasket is a dry fit item depending on compression alone for functionality whereas glazing tape depends on adhesive to make the seal between tape and glass and tape and alu profile, though the neoprene (usually) internal material of the tape requires slight compression to be watertight.

    Also it appears that the window manufacturing industry knows that alu framed in particular (but also other types) whilst initially meeting water and air ingress stds are unlikely to meet these stds in the real world for any length of time. I can well believe this since silicone is hardly the most durable weatherproofing material and it is being used on essential unsuitable joints. What a load of Bxxxxxs. Fortunately most of my windows are wood and I am renovating them/fitting DG units myself!

    Finally, it would appear a major cause of failure of gaskets is the drainage holes fitted or rather "Poor balance between air tightness of gaskets and drainage at operable vents." causing differences in air pressure to, in time, pop the gasket.
    • CommentAuthorowlman
    • CommentTimeNov 10th 2014
    If you've got gaps of 1mm all the way through then there are definitely fabrication issues IMO.
    All the alu windows I've come into contact with, it wouldn't be possible to get a Rizla paper into the joint, no pun intended.:wink:
    Yes Owlman definitely fabrication issues but only 1mm in a couple of places, mostly hairline cracks where you can see the light from outside in a straight line but then also tight in other places. I haven't got any feeler gauges, shame. If these windows had been somewhere more obvious or on display i wouldn't accept them, not a problem since the boss has already offered to take them away BUT it would be a 4 week wait if I said they had to be re fabricated as they would have to order the profiles again all at their cost - I don't think so, they would just fill everything with silicone. At least this way I can be quality control.

    Where's Monty when I need to know something about windows?:confused:
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