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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.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    Hi all,

    So, having been bogged down in planning yet again, I've decided to use my time constructively by reading up about cold-bridge free timber frame construction; twin-wall/larsen truss.

    So, my question is - our house is currently specified as a SIP construction + 100mm internal rigid insulation and single skin brick cladding. From my understanding, a larsen truss sits on the outside of the structural timber frame and is stuffed full of insulation, preventing thermal bridging through the studs.

    So, is there a reason that I can't put that up against a brick skin? All the examples I've seen have been rendered or weatherboarded (in the USA). Our planning is very restrictive and our officer is having kittens at some of the elevations having zinc, the brick is our compromise.

    What thickness would the wall have to be to get to around 0.1 u value? We are currently looking at about 325mm excluding the brick skin.

    I think I need an idiots guide to timber framing vs SIP. Blockwork is pretty much out as we need a speedy construction method due to access issues.

    • CommentAuthortony
    • CommentTimeJul 21st 2015
    I have been having a lot of trouble with SIPs makers being awkward about adding insulation. There are issues around the inherent bridging and these get worse the better the u values get.
    • CommentAuthorringi
    • CommentTimeJul 21st 2015
    Are brick slips a option? If so ICF may work for you, if you can get a pump to reach.
    • CommentAuthorPaulJ
    • CommentTimeJul 21st 2015
    Why the 0.1 target? Is it something arbitrary? I think you can do PH with a higher value.
    Hi all,

    thanks for the comments - some answers for you.

    Tony - our supplier is happy enough with us adding insulation to the inside, and a condensation risk analysis came back fine. The bridging is my concern, although mainly at the floor/wall junction as they use insulated splines for joining.

    ringi - unfortunately, probably not as we are in a medieval conservation area and "authentic" materials are pretty much a must. We also have medieval style access too, with no-where to park a pump!

    PaulJ - yes, arbitrary, although I had read this is a good target to aim for, I'm aware its difficult to achieve so I would settle for a bit less. I'm v aware that we're only going to do this once, so I want to get it as future-proof as possible.

    Has anyone had any experience with the passive house/timber frame kits supplied by MCB and the like? Would you trust them to get the details/airtightness right? This is what I'm a bit paranoid about, although who's to say I'd be anywhere near as good!

    • CommentAuthortony
    • CommentTimeJul 22nd 2015
    Re SIPs and condensation risk, the problem with insulation inside is that it makes the sole plate colder. I have concerns about damp forming on top of the dpm under the sole plates and as these are structural ....

    Why won't they allow insulation on the outside.

    On one project we have got approval for this but it was difficult.

    I would ask who is responsible for the soleplate and is it in their guarantee.
    • CommentAuthorDarylP
    • CommentTimeJul 22nd 2015
    Tony, KS have now released 'approved details' for their Tek system, utilising external insulation to the o/s of the SIP.
    • CommentAuthortony
    • CommentTimeJul 22nd 2015
    Put that down to us, can you post a link or picture please
    Interesting that Kingspan have released a detail now, thanks for letting me know about that Daryl.

    Tony, we did have discussions about the sole plate and had considered adding a small amount of insulation to cover it as part of the wing insulation for the founds. The issue was that as a lot of the building is brick clad, had we had 100mm external insulation, we would have needed another/wider set of founds, which was going to add considerable cost to the build.
    • CommentTimeJul 22nd 2015
    Posted By: divorcingjackHas anyone had any experience with the passive house/timber frame kits supplied by MCB and the like? Would you trust them to get the details/airtightness right?

    I suggest looking at the ebuild forum for the answers to these questions. Jeremy Harris, who once was here, has one and so do various other people. Jeremy is certainly happy.
    • CommentAuthorDarylP
    • CommentTimeJul 22nd 2015
    This is from KS....illustrating ext. ins., although the Nilvent is thus redundant!:bigsmile:
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