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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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    • CommentAuthorgravelld
    • CommentTimeNov 7th 2018 edited
     
    We'll be replacing our windows in our masonry cavity build. The window manufacturer recommends the use of lugs (straps) to fasten the window to the inside. Their standard minimum install spec continues with Compriband in the gap to the outside, foam to the inside. Fixing through the frame is also an option.

    I also want to tape the inside to the internal leaf and have the tape meet the internal air barrier.

    I'm not sure what to do about the internal reveals (mostly wet plastered, but some plasterboard too).

    *The lug approach*
    We're going to need to knock the plaster out of the internal reveals to fit the lugs.

    If we want to tape, we're going to need a "channel" of reveal cut that currently meets the window, I think. Then prime the blockwork as per the tape manufacturer's instructions, tape, then plaster over the lugs and tape.

    Feels like we might as well take out the entire reveal and insulate the reveal with something high performance (aerogel, phenolic, VIPs?) at the same time. Thoughts?

    To what extent can we make this good, meeting the existing plaster on the internal facing wall? How do we improve our chances of a decent looking result?

    *Fixing through the frame approach*
    Would there be another lower impact approach? Could we fix the window through the frame, tape to the existing reveal and then have a thin layer of plaster over the top of that and the rest of the reveal?

    Refs:
    - VIPs used at window reveal in Cumberworth retrofit: https://www.greenbuildingstore.co.uk/insulating-window-reveals-cumberworth-radical-retrofit/ (but in our case I want to retain the existing plaster on the main wall)

    Notes:
    - Fixing the window through the frame is still an option, but it feels like if we're taping too we're going to have to do something to the reveal...
    • CommentAuthortony
    • CommentTimeNov 7th 2018
     
    Fix through the frame but do nor deform, bend or twist it
    • CommentAuthorgravelld
    • CommentTimeNov 7th 2018 edited
     
    So if I do that, I can tape to the existing internal plaster layer, but then what to do over the top of the tape?

    The installers don't seem keen on fixing through the frames but acknowledge it can be done. Not sure if it's because the potential for the customer not accepting any kind of damage, or just because it doesn't show off their product to its best.
    • CommentAuthorgravelld
    • CommentTimeNov 10th 2018
     
    So... that works for the wet plastered reveals.

    What about the plasterboarded ones?

    The reality is this house has no air barrier. Stripping out all plasterboard and wet plastering is not going to happen just yet.

    Maybe I should just leave the taping on those windows until we strip out the plasterboard?
    • CommentAuthorwookey
    • CommentTimeNov 12th 2018
     
    I took all the plaster off the reveals. Fixed windows with foam and lugs screwed into reveals. Cut out bricks across end of reveal so I could insulate cavity all the way out the end of reveal. Carefully sealed up reveals with PUR and foam. Put 25mm PUR around reveals (glued in place), partly covering frame. Sealed that to wall plaster/insulation. taped window to PUR in reveals. PLasterboard over PUR in reveals to cover tape and provide smooth paintable finish.

    Does that help?
    • CommentAuthorgravelld
    • CommentTimeNov 12th 2018 edited
     
    It (kind of) does... I think I saw one of your older posts before I posted, so thanks for that, it provided some ideas.

    How do you remove plaster while not removing the internal facing wall's plaster? Does a bolster held parallel to the internal wall work or do you cut out a line with a grinder then start bashing?

    Posted By: wookeyCut out bricks across end of reveal so I could insulate cavity all the way out the end of reveal.
    Do you mean bricks used to seal the cavity? Did you use cavity closers?

    Posted By: wookeyCarefully sealed up reveals with PUR and foam. Put 25mm PUR around reveals (glued in place), partly covering frame

    What are the differences between the two sets of PUR? Or is the first set DIY cavity closers?

    Posted By: wookeyPLasterboard over PUR in reveals to cover tape and provide smooth paintable finish.

    What did you do where the ends of the plasterboard are flush (or not) with the internal wall? Do you do a plaster skim to finish flush with the existing plaster?
    • CommentAuthorSprocket
    • CommentTime6 days ago edited
     
    We took the reveals back to stone, put Spacetherm aerogel over the top, then EML over that to take the plasterwork. The inner membrane was in there somewhere, over the aerogel presumably, all the way to the frames.

    Anyway, it worked a treat so we did all the other reveals the same way... I've checked it with a Fluke imager when it is cold and blowy out and the whole lot is pretty invisible thermally.

    These were pretty deep (like 400+ mm) reveals in a rubble-stone building, internally insulated.
    • CommentAuthorgravelld
    • CommentTime6 days ago
     
    Thanks - what is an EML?

    And how easily can the plasterwork in the reveals meet the internal facing wall?
  1.  
    Thanks - what is an EML?

    Expanded Metal Lathing.

    And how easily can the plasterwork in the reveals meet the internal facing wall?

    Use the tightest angle bead you can, and cut it into the facing plaster. 3mm min. should do.
    • CommentAuthorgravelld
    • CommentTime4 days ago
     
    Thanks Nick.
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