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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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    • CommentAuthorCX23882
    • CommentTimeJul 31st 2022 edited
    I have some secondary glazing currently being manufactured. It's an aluminium double-glazed system which I'll be fitting on the "room" side of the reveal. Primary reason for fitting it is to reduce road noise (hence the large air gap), and existing windows' have a pane of low-e glass (albeit hard-coat), so any insulating properties are a secondary benefit. I didn't want the secondary glazing to have too good a u-value on its own, because of the risk of making the cavity between the windows too cool, but it should still be an improvement, and figured I can always upgrade the primary windows later on.

    What is the best approach for sealing the frame against the reveal?

    I know many windows get installed with expanding foam, but the stuff makes such a mess no matter how carefully it's applied. Since the secondary glazing has a hollow profile, I was thinking about sticking Compriband expanding tape within the outer "U" of the profile, so that it expands out against the reveal on all 4 sides. Then, I would finish with a bead of sealant inside and "out" and then trims.

    I've never used Compriband before. Is it realistic to expect that I would be able to open a roll of it, stick it to the frame (2.4m x 1.2m), and get the frame in place before it has expanded too much (i.e. before it becomes larger than the reveal opening)? I was thinking of a dry-run fit, where I pre-drill all the necessary holes for the actual fixing, stick the Compriband on, and then go for it.

    Or should I just go with expanding foam?
    • CommentAuthorowlman
    • CommentTimeJul 31st 2022
    I've used expanding tape quite a bit when fitting wood sections to uneven walls: e.g. behind oak skirtings to old clamp brick walls although not the brand name you mention. There are difficulties using it however, as you allude. If you're sticking aluminium extrusions direct to a wall do all the drilling and plugging (dry) beforehand.
    Once you unroll the stuff it starts to expand so don't do too much at once. If you're carful with the application to you'll get a very neat result,- set it back from the edge half a mm or so.
    Rather than going for the over the counter stuff contact a specialist supplier as they'll have tapes with different widths and expansion rates. The rolls come compressed and once you start you'll need to finish straight away, as the stuff will expand in the roll.
    As a project I'd be tempted to fit a machined wood, polished? " ground" all round the reveal first then fit the alu. extrusion straight to that The wood base can be discrete as you want. This way you can get the eventual sizing exact.
    Use expanding foam with an applicator gun and a very fine nozzle hole and maybe even low expansion foam.
    • CommentAuthortony
    • CommentTimeJul 31st 2022
    I like positive against the frame rather than butting the frame to the reveal. Fit a trim or acoustic board in the reveal and seal the frame of the new glazing to that invisible in the reveal.
    • CommentTimeJul 31st 2022
    Posted By: tonyFit a trim or acoustic board in the reveal and seal the frame of the new glazing to that invisible in the reveal.
    Not sure what you mean there, Tony?
    • CommentAuthortony
    • CommentTimeJul 31st 2022
    Will you fit some acoustic board between the new and old frames round inside the reveal?
    • CommentAuthorrevor
    • CommentTimeAug 1st 2022
    Things I found useful in using expanding foam tape is put in the fridge overnight before use do not if you can help it use on a warm day. Make sure none of the tape protrudes outward i.e must be below the 2 edges of the gap otherwise it will blow outward when it expands. Do not remove all the release tape all at once. Peel back a bit of the start turn over and out the leading edge to give you a hold and as you inset the tape pull off the release paper gently (it can tear) as you go along positioning the tape. Not quite sure what the installation detail is, a sketch would help me to comment.
    • CommentAuthorSimonD
    • CommentTime7 days ago edited
    Posted By: tonyI like positive against the frame rather than butting the frame to the reveal. Fit a trim or acoustic board in the reveal and seal the frame of the new glazing to that invisible in the reveal.

    This definitely get my vote. You can then put some expanding foam tape around the back edge of the new secondary glazing, push it tight to this new reveal and fix into place.

    Posted By: djhNot sure what you mean there, Tony?

    I'm assuming that he means you fix acoustic board, or it could just be a timber batten, around the existing reveal, so that it creates a lip inside the existing reveal. The secondary glazing then gets pushed against that.
    • CommentAuthortony
    • CommentTime7 days ago
    Yes, thanks Simon
    • CommentAuthorCX23882
    • CommentTime5 days ago
    Thank you for all your replies.

    I hadn't considered sealing against some new trim/battens, but that makes sense from a practical standpoint. It certainly seems that approach could be less problematic.

    I've done a very rough MS Paint sketch (just the outer frame is shown, not the panels):
    - The red rectangles are where I originally planned on sticking the foam. The top frame piece is a bit of a challenge since the drawings show a stiffening rib along the middle, meaning that the foam can only be narrow in width which isn't ideal. The bottom frame piece has a slight slope, but I don't think that's a problem.
    - If I'm understanding Tony's suggestion - the brown boxes are some new trim pieces which I would fix all around the reveal. The purple rectangles indicate where the foam will be stuck - to seal the face of the secondary glazing frame against the size of the new trim pieces.
    - The gold/yellow lines+circles indicate where fixings will go - i.e. through the battens/trim, and also through the bottoms of the tracks of the frame (need to check this once the frames arrive)
    • CommentAuthorrevor
    • CommentTime5 days ago
    You can use EPDM seal with one adhesive side instead of using compriband it will be cheaper and much easier. I Think that is all you need. I can't work out how you are going to get the DG in as looks like your brown trims are in the way. I do not see the need for these what you have drawn will work well and is how I would have approached the job with some packers to align the frame in the reveal. I would fit the seal up against the reveal to complete an acoustic seal so there is no gap as you have drawn it. Finish of the frame face with some architrave trim to hide any sealant and job is a good one
    • CommentAuthorowlman
    • CommentTime4 days ago
    @ CX23882.
    Had you considered hinged secondary units? From the drawing it looks like they are sliding panes. The usual recommended air gap, primary to secondary glazing is 100 - 200mm.
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