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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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    • CommentAuthorAshley
    • CommentTimeNov 20th 2019
    Hi everyone,

    We recently moved in to a 1950s built property which is proving to be very cold. In the last month I have completely upgraded the loft insulation to ~450mm, but still I'm looking to other ways of making the house warmer.

    The walls have a cavity and CWI was added at some point in the property's history.

    The house had an extension added in the 1970s which consisted of a garage with bedroom above. When the CWI was done the wall between the garage and the property was not filled with insulation (which is one wall of our dining room).

    Furthermore, I have seen in the loft that the cavity for this wall is fully open at the top - so warmth will be traveling through the wall in to the cavity and then straight out in to the loft.

    I have read that with properties of this age that electric cables could run through the cavity walls, and indeed the electrical fuse board is sited on that wall in the garage. I am therefore reluctant to add CWI beads.

    My current thinking is to use normal loft insulation to block up the cavity in the loft, and then to attach insulation to the wall in the garage. I'm unsure as to the best insulation to use - std Celotex board, EWI, something else?

    As an alternative , I have read that a product called silvapor could be used to fill the cavity. Does anyone have any experience of this or indeed know what it costs? There seems very little info on this.

    Are there any other options I should consider, or any pitfalls I am missing?

    Thanks in advance for any help,

    Lots of cavities have a gale blowing through them so before you go down the route of blocking the top of the cavity and insulating the garage side make sure the cavity doesn't have air flow through it otherwise you will be wasting your time/money. Adding EWI without proper CWI generally doesn't help much. If you do decide to EWI the garage/house party wall then I would use standard EPS EWI materials, (adhesive, EPS, adhesive + glass mesh render, colour render to finish) and I would fix OSB over the EWI as mechanical protection.

    Whilst the fuse board may be on the garage wall this doesn't guarantee that the wiring is in the cavity (rather than passing through). If you can access the top of the cavity to look in with a torch you may be able to confirm the presence of cabling.

    What is the insulation between the garage ceiling and the bedroom floor? This could also be an area for improvement.

    Whilst the property has had CWI it would be worth checking the effectiveness of the CWI because quite a few CWI jobs were not done properly leaving voids.
    • CommentAuthorAshley
    • CommentTimeNov 20th 2019
    thanks Peter - I'm not sure how I check the air flow of the cavity...it is pretty cramped in the loft but I may be able to look down...where else could air get in? First floor joists?

    yes checking the insulation between garage ceiling and bedroom floor is on my list - I think it is minimal but the ceiling boards were flagged as asbestos by our surveyor during the purchase so have to wait.

    If cables pass through the cavity, doesn't that still pose a problem with using CWI?

    • CommentTimeNov 20th 2019
    Posted By: Ashleyit is pretty cramped in the loft but I may be able to look down

    It may be worth investing in an endoscopic camera. They are fairly reasonably priced nowadays.

    If you carefully locate all electrical cables in the wall, it might be easier to reroute them or enclose them in a conduit so you can use conventional EPS beads to insulate the cavity.
    • CommentAuthorAshley
    • CommentTimeNov 20th 2019 edited
    thanks djh - hadn't thought of that.

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