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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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    Hi! We have our timber frame going up in a few weeks. There are a number of steels that are in the walls, and we are looking at possible ways of insulating them and thermally breaking them. The overall U value for the walls which consist of rockwool at 140mm and a 40mm PIR lining board is 0.17. We have looked at the 10mm spacetherm which looks ok but expensive (over £1000). With a 40mm PIR liner internally, does anyone know if there would be a huge benefit to using the spacetherm. I was also considering using 25mm PIR in the exterior cavity over the steels instead of the spacetherm as it shouldn't disrupt the airflow any more than the 25mm battens we are using elsewhere. Any thoughts would be much appreciated.

    • CommentAuthorrevor
    • CommentTimeOct 16th 2020
    Having difficulty visualising the position of the steels in the wall. Have you got a cross section sketch that you could post. Presumably architect /SE been involved what have they got to say.
    • CommentAuthortony
    • CommentTimeOct 16th 2020
    will the steel be inside or outside the thermal envelope?
    Hi guys,

    I have attached the plans below. I have designed the house myself and the timber frame company did the actual frame design so no architect. The steels are in the stud walls as you can see from the drawings. Any thoughts would be helpful!
    Here is the other plan
    • CommentTime7 days ago
    You maybe want to upload higher-resolution images to someplace and link to them. It's not clear where the steels are on the images you're limited to on this site.
    • CommentTime6 days ago
    Well I can see enough - socking great steel stanchions extending (on plan section) from just inside the cladding (?) and projecting into the room, in two places. Huge conductors, efficiently radiating midwinter into the room! They'll have to be boxed around internally at decent thickness, even if using super-insulative material.

    What happens overhead? Do they support a horizontal beam similarly penetrating the roof thermal envelope?
    • CommentAuthorrevor
    • CommentTime6 days ago
    A sectional detail around the stanchions and frame would be useful as I cannot make out with sufficient clarity. Presumably it is a 2 storey house so the steels supporting upper floor will need fire proofing. If you have them painted with intumescent paint it will be easier than fireproofing by boxing in. It is a mistake I made and it was far more effort to box in it is easier to paint.
    Difficult to see, but looks like you'll have several different details, all with quite different possible solutions. A column, maybe a 150x150 UC? with a beam face fixed. Beam tail starting on the timber frame. Beam running along an external wall face. Beam as a cantilever to outside.

    Draw every detail, and that in itself will start to unravel the conundrum. Air tightness must be brought into the buildup too, for example laying in pieces of membrane as the structure goes up, so you're not trying to stick tape around beams, joists, joist hangers, etc.

    Build it on paper first, then you might get 80% of where you'd like to be.

    Share the drawings on here, let us help you pick it apart.
    • CommentAuthordickster
    • CommentTime2 days ago
    Ours was built with an A frame steel within the insulated (blown paper) walls/roof of the house. I made a great song and dance about the steels needing a thermal break where the verticals poked down through the walls between the brickwork/blockwork apron air brick ventilated cavity and onto the concrete raft (non insulated).

    Both architect and builder not interested, stating that it was not necessary. My view was that the let's say -12C base of steel going straight up into warm wall would be a condensatory disaster. I lost out on this one.

    Suffice to say that upon later inspections in cold/humid conditions the steel both internally and externally remains bone dry. The additional heat loss no doubt is negligable. No cold spots or mould growth.
    • CommentAuthorCWatters
    • CommentTime1 day ago
    Aerogel wrap..


    Probably need fire rated plasterboard as well.
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