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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthormatt1
    • CommentTimeApr 16th 2018
     
    I am currently in the middle of a self build using a timber frame system. The windows have now been installed in the frame and I am looking at using pro-clima tescon profile tape inside to seal them before the plasterboard goes on.

    Before doing this I was advised to use expanding foam in the gaps between the window and the frame however many of the gaps are too small to fit even a small expanding foam nozzle in (1-2mm) at the smallest. Am I ok to leave these gaps and rely on the tape or is there a method I am missing to get the foam in?
    • CommentAuthorgravelld
    • CommentTimeApr 16th 2018
     
    I've used one of those syringes for filling inkjet cartridges clamped on. Also I think JSHarris came up with a much better engineered approach. But first you need to work out whether this is even the right thing to do.
    • CommentAuthormatt1
    • CommentTimeApr 16th 2018
     
    Sounds good, how did you attach the syringe to the foam gun?
    • CommentAuthorHats
    • CommentTimeApr 16th 2018
     
    May not work in this situation but i needed to seal between some joints in uneven timber, only a few mm but you could feel the wind... i drilled a few holes the same size as the nozel along the length of the timbers (in the offending gap) and just squirted foam in, worked really well ! Cut back the foam and taped. Job done.
    • CommentAuthortony
    • CommentTimeApr 16th 2018
     
    Acrylic sealant?
    • CommentAuthorgyrogear
    • CommentTimeApr 16th 2018
     
    Posted By: Hatsi drilled a few holes the same size as the nozle along the length of the timbers (in the offending gap) and just squirted foam in, worked really well


    Good idea, I'll have to give that a try...

    gg
  1.  
    This stuff was one of our favourite products while building.

    http://www.coldstop.co.uk/products/other/view/58b0644183a745715ca97197/omega-liquid-sealing-compound

    Ideal for sealing gaps too small for foam and easier to use than acrylic. Also really good for temporary waterproofing (on timber that will later be covered) and as a secondary back up waterproof layer. we used it all over the place.
    • CommentAuthormatt1
    • CommentTimeApr 17th 2018
     
    Thanks for the suggestions I will be trying the sealing compound and may well drill some holes around the frame too.
    • CommentAuthorgyrogear
    • CommentTimeApr 17th 2018
     
    I suspect that simple PVA ("white wood glue") would also do the business just as well... will give it a try & report back...

    gg
    • CommentAuthorSilky
    • CommentTimeOct 31st 2019 edited
     
    just looking for some advice from expierience on this topic, just about to frame up my outie windows ( in facade ) and manufacturer instruction for minimum sealing gap is 8mm. Therefore nominal is 10, I could go bigger, 15 or 20 mm, will it make my life any easier, make the job cleaner or quicker? I'm also thinking of long term movement of the building, frame etc, any disadvantasge to going bigger?

    For the sealing I think it will be compriband 1 side, flexifoam in the middle and a simple foam strip on the otherside ( don't have the working order for this in my head at the moment ). There will be a strip of breather membrane taped around the frame which will then be joined up to the 'internal' membrane with Tescon after the window is installed, so air detail will be good. The frame is 120mm deep.
    • CommentAuthorcjard
    • CommentTimeOct 31st 2019
     
    I found that a silicone sealant nozzle would fit on the foam gun jsut by pushing the gun into the nozzle, distoring the plastic to make a seal. Then when the end of the plastic nozzle is flattened, it makes for a nice narrow nozzle for applying foam to awkward areas

    Bigger gaps are more of a nuisance to hide and seal; i'd keep the gap to the 8mm recommended

    Also be aware that the 2 part foam eg https://www.abbuildingproducts.co.uk/general-building-materials/expanding-foam-insulation/touch-n-foam-15-kit-complete.html is far superior to enaything that comes in a single can; the 2 part stuff ends up more like PUR/PIR board foam in terms of rigidity and consistency. The single cans of expanding foam are open cell (i was told) and ever so slightly leaky.

    If using 2 part foam appraise yourself of how much it expands, and maybe mask off the surface finish of your windows as it sticks to (eats into) powder coat really well.. Ask me how i know :)
    • CommentAuthorcjard
    • CommentTimeOct 31st 2019
     
    PS; the two part foams are available for less as a two cans of liquid that you mix and wait for the reaction. You can get reasonable control by using a plastic bottle with a bit of straw poked through a hole drilled in the cap, mix a small amount, squirt it onto surfaces (eg the brick/frame) at the top (so it runs down. if you start at the bottom it will majority collect there and go crazy) and wait for the expansion to bridge the gap

    The liquid (and the foam) products are highly temperature dependent; they don't expand anywhere near as well if sitting on a cold surface. Pre-warming if particularly wintry, is advised
  2.  
    A photo of a gap I recently filled with basic sqirty foam from a can, it mushrooms pleasing out of the crack, however when cut back, it clearly is not remotely airtight. It's not sold as such. The bubbles join together into bigger voids.

    I use it as 'bulk' gap filler but cover it with flexible goo where airtightness is required.
      IMG_20190916_092457518-2080x1560.jpg
    • CommentAuthorgyrogear
    • CommentTimeNov 1st 2019
     
    I seem remember reading somewhere that the secret to using this stuff, is to pre-spray the cavity with soapy water first, to encourage the foam to "follow the wet". However, I have not personally tested this (yet...).

    gg
  3.  
    Yes, I do that too (with clean water no soap)
    • CommentAuthorSilky
    • CommentTimeNov 1st 2019
     
    Thanks for the tips, yes that is why I was thinking Flexifoam as it is also meant to be airtight and absorb some movement. But it doesn't expand as much and fill as well as regular fixing foam and tends to clog more. I will look into the 2-component stuff too, have never tried that.
    •  
      CommentAuthordjh
    • CommentTimeNov 1st 2019
     
    Posted By: SilkyThere will be a strip of breather membrane taped around the frame which will then be joined up to the 'internal' membrane with Tescon after the window is installed

    Why breather membrane? It's normal to use a vapour control membrane on the internal side.
    • CommentAuthorSilky
    • CommentTimeNov 1st 2019 edited
     
    @djh, why breather membrane?

    yes, it shows vapour control / tight membrane in the Rehau docs that I'm looking at. I have a variable membrane over the roof rafters and then it is extended over the gable and down the outside of the old house, so it is behind the insulation + facade. The windows are sitting in the facade in front of the old wall. I didn't see sense in changing material just for the last 30 cm to join up to the window frame. I think it will be ok... or did I miss something?

    EDIT: ok, you got me thinking, could potentially a tiny ammount of moisture go through to the window area near the frame and then accumulate? hadn't occurred to me.. so if i use plastic here it will force the moisture away from the window area to where the construction is fully breathable ?
    •  
      CommentAuthordjh
    • CommentTimeNov 1st 2019
     
    Posted By: SilkyI have a variable membrane over the roof rafters and then it is extended over the gable and down the outside of the old house, so it is behind the insulation + facade. The windows are sitting in the facade in front of the old wall. I didn't see sense in changing material just for the last 30 cm to join up to the window frame.

    Sorry, apologies if I missed something but I have no idea about your project from reading this thread. I think what you're saying is that you have EWI so the outside of your existing house is actually the inside from a thermal point of view. And by variable membrane I take it you mean something like Intello. In which case, Intello meets my definition of vapour control membrane and I don't understand why you wouldn't use that instead of a breather (i.e. vapour open) membrane?
    • CommentAuthorSilky
    • CommentTimeNov 2nd 2019
     
    @djh, yeh I was obviously talking out of the proverbial slightly, the membrane is DASATOP also from Pro-Clima and similar to Intello, it is meant to keep vapour inside in the summer and let it out at cold spots (on top of the rafters) during the winter, at least according to this blurry diagram, https://www.harrer.at/img/400/300/90/data/images/HBHB_Kapitel/01_Luftdichtung/dasatop.JPG So that is why I was thinking of calling it a 'breather membrane', but that was wrong.
    • CommentAuthorLF
    • CommentTimeNov 8th 2019
     
    If using expanding foam for sealing gaps, this guy on youtube has lots of good advice and how to videos.

    I have no links to him. "Painting and Decorating"
    example.
    https://www.youtube.com/watch?v=QrKB59nZfxY

    I have been doing my windows following his methods as we decorate any rooms- house had very poorly sealed UPVC windows For thin gaps - he squeezes the tube on the can and can get in tiny gaps to get the foam in.

    Our "Tony" on here is also used extensively and his websites on drafts.
    •  
      CommentAuthordjh
    • CommentTimeNov 8th 2019
     
    The main thing with using expanding foam to seal gaps is that it is essential to use a foam that stays flexible. One of the acoustic or airtight ones. Normal foam will pull away from the surface after time.
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