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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorTimSmall
    • CommentTimeNov 5th 2018
    Last week I stuck some graphics EPS beads into the reinforcement channels of some PVC double and triple glazed windows.

    Barring a couple of minor mistakes, it went pretty smoothly.

    We used a vacuum cleaner, some plasterers' mesh scrim tape, and a 5 litre mineral water bottle (courtesy of a neighbour's recycling box).

    The outer-frame reinforcement chambers were empty in these windows (as is commonly the case) because reinforcement wasn't needed for this window size and type. They're made to accommodate steel box section reinforcement.

    Drill two holes either side of the window. Vacuum cleaner goes on one side (22mm copper pipe with mesh tape on end), bottle of EPS beads on the other side. A bit of sealant over the holes when finished.

    A calc I did in Therm showed the Uf value dropped from 1.14 to 0.88 W/m²·K.

    Sticking some insulation between the sealed unit and the frame dropped it further to 0.83 W/m²·K.

    I'll post some photos of kit and windows later on, plus some more details. The plan is to upgrade the double glazed sealed units to triple glazed too.
    Sounds neat! Looking forward to the photos.

    Does condensation form in the insulated cavity and can it still drain? This was the (spurious?) reason given to us by a fitter as to why they didn't supply the frames factory-filled with foam.
    • CommentAuthorgyrogear
    • CommentTimeNov 5th 2018
    brilliant news, thanks !

    I have got extensive aluminium DG frames (from 1993) in a Paris flat - they are real heat-sinks, so I might just give this method a go !

    • CommentAuthorTimSmall
    • CommentTimeNov 5th 2018 edited
    Posted By: gyrogear
    I have got extensive aluminium DG frames (from 1993) in a Paris flat - they are real heat-sinks, so I might just give this method a go !

    Unfortunately I don't think this will help much with aluminium frames... If the aluminium surrounds the cavity that you're considering filling, then the heat flux through the frame will dwarf that through the current air cavity, and the improvement from replacing the air with EPS will be negligible. Because aluminium conducts heat 1000x faster than PVC, the heat will just zip around the outside of the EPS through the Aluminium.

    If on the other hand they are an aluminium clad design, that would work fine, but I suspect they're not.
    • CommentAuthorTimSmall
    • CommentTimeNov 5th 2018
    Posted By: WillInAberdeenDoes condensation form in the insulated cavity and can it still drain?

    The cavity in question was previously fully sealed (apart from where window hardware and fixing screws penetrated).

    Rehau put solid EPS inserts in the reinforcement chambers of some of their PVC windows (e.g. Rehau Geneo). They also do the insulation between unit and frame thing ("Rehau THERMO" window option for their older S706 and "Edge" frames).

    After having the EPS beads idea, I googled for it, and found that Internorm have started to do the same thing on some of their Ali-clad PVC windows (e.g. Internorm KV 440).
    • CommentAuthorTimSmall
    • CommentTimeNov 5th 2018
    • CommentAuthortony
    • CommentTimeNov 6th 2018
    • CommentAuthorTimSmall
    • CommentTimeNov 7th 2018
    Some photos here.


    The last photo is a contraption that I used to fill the bottle with. I found that there were a few fused beads in the big bag I had, and this would tend to clog things up. Fill the bottle by putting the vacuum cleaner nozzle on the mesh "window" which was taped into the side of the bottle, and hold the pot with holes in the lid just above the bag. Next time I need to fill it, I'll drill a new lid with more holes, spaced closer together... 7mm holes I think.

    The "feed tube" is 15mm copper. It's attached to the bottle lid with a tank adaptor off a scrap plastic header tank. I wouldn't go any smaller than 15mm, 20mm or larger would be fine.

    I'll try and make a video for the next one we do.
    • CommentAuthorgyrogear
    • CommentTimeNov 7th 2018
    Posted By: TimSmallUnfortunately I don't think this will help much with aluminium frames...

    Thank you for that, I take your point !

    Perhaps I could try expanding PU foam...
    "nothing vented, nothing framed" :smile:

    • CommentAuthorandyman99
    • CommentTimeNov 8th 2018 edited
    I did try PU foam in PVC window frames a couple of years ago. It appeared to have some affect, as the windows actually attracted a little more condensation than non insulated ones in the same room. I'd say you need to be cautious though, I got a little carried away on one and warped the chamber slightly. OK unless you want to remove the window in the future
    • CommentAuthorTimSmall
    • CommentTimeNov 8th 2018 edited
    In an Aluminium extrusion, filling the voids with an insulating material is not going to help (well you will actually get a tiny improvement, but it'll be something like 0.1%, instead of the 20% improvement I modelled on that PVC frame).
    • CommentAuthorgyrogear
    • CommentTimeNov 8th 2018
    thanks for the valued input !

    • CommentAuthorwookey
    • CommentTimeNov 12th 2018
    I filled one of my PVC window-frames with PU foam. Requires more than 2 holes - I did holes every 15cm or so. And don't go too fast so it gets plenty of space/time to expand (to avoid warping), but it seemed to work well. I have not tried to do the numbers for how much better it is.

    Wish I'd thought of it earlier so I could have done it on all the windows that have been retained.
    • CommentAuthorRobL
    • CommentTimeNov 12th 2018
    I filled the parts of my uPVC frames exposed when I changed DG units 5 or 6 years back, except for parts that just might get water dripping in/through. I drilled a 7mm dia hole every foot or so and squirted foam in like it was going out of fashion. No problems other than messy cleaning up the foam that came out of holes.
    Good reminder - I still have a few box sections I can get to when you open windows. I didn't do it at the time as I had lots to do, and it was a job I could put off.
    • CommentAuthorTimSmall
    • CommentTimeNov 24th 2018
    We filled two windows with the beads in-situ.

    With 1-part PU foam, I wasn't sure the foam would set before it slumped, since it is moisture-cured. I think you should get a slightly better U value with graphite EPS beads too...

    You can vacuum the beads into things like sill sections in a very satisfying way...

    Stick the vacuum cleaner nozzle (with mesh over the end) at one end of the sill section, and then put the other end of the sill on a flat surface (preferably indoors, or on a windless day), and pour beads from the bottle (see photos above) onto the surface - the beads enthusiastically rush to fill the hole. Tamp the end to lock them into the channel.

    After you've finished, move the vacuum nozzle to the mesh hole in the bottle, and vacuum excess beads up from the flat surface back into the bottle.

    I see Sika do a few different silicones for "structural window bonding" - to remove the need for reinforcement (so that they use the glass for rigidity instead), but these seem to be two-part silicones, which I imagine are hard to get hold of, and require relatively expensive kit to apply. Maybe there are similar one-part silicones which could be used instead (albeit with a much longer cure time).
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