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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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    • CommentAuthorLuke.Smith
    • CommentTimeNov 15th 2019
    Not quite as drastic as the discussion topic suggests but I have a decent amount of tissue faced (no foil) Kooltherm K103 50mm phenolic foam board insulation left over from a floor insulation job.

    I then have an attached garage where the separating wall is single skin 5" block. Anyone see any issue with the idea of me using spray adhesive to stick the phenolic to 11mm OSB sheet and then mechanically fixing that to the cold side of the wall (garage side)?

    Phenolic presumably closed cell, then tissue faced so no form of vapour barrier in what I'm proposing but are there any real issues I should be aware of despite cold side application to sheltered garage side?? Wall is a 5m length, approx 12m2.

    Many thanks in advance!
    • CommentAuthortony
    • CommentTimeNov 15th 2019
    Wall-adhesive-foam board- osb?

    The thin OSB will deform and pull away, it will also be a fire hazard .
    • CommentAuthorjms452
    • CommentTimeNov 16th 2019
    So the insulation goes in the garage and the osb is to protect it from knocks?
    Phenolic is fire proof.
    Would painted osb3 handle the location?
    How about fixing with baton over then feather edge cladding, that would allow ventilation around the cladding
    • CommentAuthorLuke.Smith
    • CommentTimeNov 16th 2019

    To clarify what's proposed:

    block wall - 50mm phenolic foam board - adhesive - 11mm osb. All mechanically fixed back to block wall.

    Appreciate the fixings would bridge the insulation. I could also up it to 18mm OSB for a bit more rigidity. OSB only really intended to provide a bit of protection - I could stand it off on battens but is ventilation between the insulation and osb neccessary?

    Thanks again

    • CommentTimeNov 16th 2019
    Use stainless steel fixings to reduce thermal bridging (8x less conductive than mild steel IIRC). That's what I did for my aerogel IWI.


    • CommentTimeNov 16th 2019
    Posted By: DamonHDUse stainless steel fixings to reduce thermal bridging (8x less conductive than mild steel IIRC).

    Agree with the recommendation but I think you're a bit optimistic on the benefit. Stainless 14+, worst steel 54, ratio < 4 source: https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html
    • CommentAuthortony
    • CommentTimeNov 17th 2019
    I use nylon insulation fixings with plastic expansion nails

    Still donโ€™t like the wood ๐Ÿ™
    • CommentTimeNov 17th 2019 edited
    No one is daring to opine on Luke's central question
    Posted By: Luke.Smithare there any real issues I should be aware of despite cold side application to sheltered garage side?
    Posted By: Luke.Smithis ventilation between the insulation and osb neccessary?
    • CommentTimeNov 17th 2019
    I for one don't understand whether this 'EWI' is actually external, in which case using OSB as the outside face is crazy, or is actually inside the garage, but external to the house, in which case the questions about fire risk become relevant?
    • CommentAuthorgyrogear
    • CommentTimeNov 17th 2019
    Posted By: Luke.Smithusing spray adhesive to stick the phenolic to 11mm OSB sheet

    What is the purpose of the OSB ? (what is the purpose of the adhesive ?) ? (would double-backed tape do ?)
    Is the garage used as a... garage ? or some other function (storage, bike shed, workshop, music room... ?)
    What do building & fire regulations etc. say about the wall between the garage and the habitable volume ?

    sorry for all the questions...


    (My garage/house wall is 20-cm concrete blocks, I left it bare on the garge side, and did IWI on the other side).
    Argh , yes. I thought it was external insulation.
    Is it Luke?
    • CommentAuthorLuke.Smith
    • CommentTimeNov 17th 2019
    Sorry chaps - and do all appreciate you giveing this some thought for me!

    Yes, it is proposed that this insulation goes garage side of the wall i.e. inside the garage which is still used as a garage. Cold but sheltered. OSB proposed just to protect the insulation from impact damage etc.

    Double sided tape may well do it. Just trying to create a panel I can readily fix to the wall.

    I get the concern about fire risk but garage also already cotains petrol, spririts, paint, aerosols and loads of timber so I'm not too sure I'm bothered about what might become a little more fuel tbh!
    • CommentAuthorgyrogear
    • CommentTimeNov 17th 2019
    Maybe plasterboard would be a better / cheaper option ?
    Would also accept impacts from your car doors, without damaging the latter !

    (been there, got the T-shirt - my wife loves parking alongside our Granite Wall...) :shamed:

    • CommentTimeNov 17th 2019
    Posted By: gyrogearMaybe plasterboard would be a better / cheaper option?

    Dunno about cheaper but a tile backer board or similar fibre-reinforced cement board would be fireproof and impact resistant.
    Fermacell lining board (gypsum-based plasterboard substitute) is supposedly strong enough to fix shelves to directly, and resists impacts fires and noise. I've never used it but other folks on GBF have been keen.

    Stainless is less thermally conductive than mild steel, but also less strong, so you need more (or fatter) stainless screws for the same wall, which reduces the thermal benefit. Plus it's rather expensive.
    • CommentAuthorwookey
    • CommentTimeNov 19th 2019
    I did this in my garage, but used 100mm phenolic (mostly because brick pillars already had 100mm standoff), and MgO (magnesium oxide) boards. These are _much_ tougher than plasterboard and not at all burnable. I did put 50mm battens into wall so as not to rely only on the board for lots of really heavily-loaded shelving, but by being only half-depth, no thermal bridge except frame fixings.

    OSB will also work but won't look as nice and will need to be thicker for same strength. There are quite a few MgO board suppliers now. e.g. https://www.constructshieldproducts.com/mgo. I used 'Resistant Multi-pro': https://www.resistant.co.uk/products/multi-pro/
    They are not quite tough enough to be used as flooring (they get scuffed after a few years), but very good for walls.
    I also had a party wall between house and garage, although the wall in question was 50cm stone/rubble wall. I put 100mm EPS on the garage side with standard EWI adhesive and then screwed 3 tile battens horizontally measured to be at the top, middle and bottom of a horizontal sheet of OSB and then screwed the OSB to the battens. The void created by the battens was used to run some power sockets and a couple of light switches. The void was a function of the fixing method rather than any perceived need for a void and the OSB was put up to protect the insulation from abrasion. I used the batten method because screwing to a stone wall is a pain and I could get decent(ish) fixings on the battens every meter or so and then screw the OSB every 30cm or so. 10mm OSB used.

    Job done some 6 years ago and no problems so far. Oh and the aesthetic value of the OSB was acceptable !
    • CommentTimeNov 19th 2019
    Not quite the same, but in two garages recenbtly converted, one to consulting room, one to utility room, we used birch ply as the facing, carefully done/screw pattern, v-jointed. Looks wonderful! Can hang hooks, uprights etc from it.
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