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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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  1.  
    Hi, We have just had new trusses fitted. We need to plan how to insulate the roof and loft floor spaces. I have done a search on here for a guide but can't see one. Can anyone give us a link or outline in simple terms best methods? Roofing store recommended an integrated membrane and insulation- TLX but we are unsure what would be best ! Many thanks for your help.
  2.  
    Can you post pics showing space available, and any restrictions in depth, at eaves, for example? Is there scope for a warm roof, with insulation above the rafters, or a hybrid warm roof, with insulation above and between the rafters. There's a rule of thumb which suggests that in a hybrid roof 2/3 of the overall thickness should be above the rafters.

    I would keep membrane and insulation separate. With the exception of vacuum panels, a thin thing tends to have the insulation value of a thin thing, so why not hang the uninsulated thin thing at the top, and have fat insulation below?
    • CommentAuthorgyrogear
    • CommentTime4 days ago edited
     
    Best way to insulate new roof ?

    Well, the best way to insulate a new roof (IMALO) is to make a sealed warm roof...
    (a logical follow-on to the fact that the best way to insulate the walls, is EWI...).

    The OP asks for the "best way", then reveals that he has already opted for a sub-optimal way !!


    <blockquote><cite>Posted By: Nick Parsons</cite>There's a rule of thumb which suggests that in a hybrid roof 2/3 of the overall thickness should be above the rafters</blockquote>

    Er, not nit-picking, but I think that the rule of thumb suggests that it is 2/3 (or 3/8ths or 11/16ths or whatever...) of the *insulative power* that should lie above the rafters...

    gg
  3.  
    gg, if I understand your comment as you meant it, (I think!) you are probably right. I assumed that it was the same insulant between and above, but I think you are making the point that it's effectively two-thirds/one third of *total R value of insulation* - worth remembering if, for example, you are using, say, rockwool , with a Lambda of 0.040W/mK, between the rafters and Pu with a Lambda of 0.022 above. Is that what you meant?
    • CommentAuthorgyrogear
    • CommentTime4 days ago
     
    Yes Nick, it was precisely that (for example, I have PU foam external, and EPS internal...).

    gg
  4.  
    Hi, I can have a go at posting some pictures of the trusses if I can work out how to do that.

    I need a really basic intro - roofing insulation for dummies if anyone can guide me please ?
    eg keep insulation and membrane separate, consider x, don't use y

    Please take into account that some of us are absolute beginners and may well make mistakes - suboptimal decisions - we all need help ! I was hoping there might be a friendly person out there who can give advice ?

    Thanks
    • CommentAuthortony
    • CommentTime4 days ago
     
    I would say use glass, mineral or ecowool quilt at ceiling level, fill between trusses. Then additional 200mm over the top. The opposite way, raised deck with 50mm clear ventilation gap. I used 50 x 47 props and 50 x 47 rails on rop of trusses and osb deck

    http://www.tonyshouse.readinguk.org/icon/house72.JPG Not all the insulation is in yet, I had 500mm
    •  
      CommentAuthordjh
    • CommentTime4 days ago
     
    Well as it says at the left:

    Green Building Bible, Fourth Edition

    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.
  5.  
    Thanks for your help Tony and DJH.
    • CommentAuthorgravelld
    • CommentTime3 days ago
     
    Anyone know what this is:

    http://www.greenbuildingbible.co.uk/

    ??? Reads like something rather scammy?

    Is there a sample chapter for the GBB, I'd rather know what kind of detail is has. Amazon reviews give a general feel.
    • CommentAuthorCWatters
    • CommentTime2 days ago
     
    Newcastlerenovation: Are these atic trusses? Is there a room in the roof? If not then hard to beat putting 500mm or more of rockwool at ceiling level.
    • CommentAuthorgravelld
    • CommentTime2 days ago
     
    Except try doing that at the eaves, and what about all the timber bridges at the eaves where joists connect to rafters?
    • CommentAuthortony
    • CommentTime2 days ago
     
    Been there, done that, got the tea shirt

    http://www.tonyshouse.readinguk.org/mitigation.jpg

    And insulate over the wall plate before felt and batten otherwise impossible to do http://www.tonyshouse.readinguk.org/icon/house49.JPG
    • CommentAuthorgravelld
    • CommentTime1 day ago
     
    Yes but the bit where the bread knife is is what I'm talking about as a bridge.

    Probably not significant.
    • CommentAuthortony
    • CommentTime1 day ago edited
     
    Usually it is not possible to introduce any insulation over the wall plate, I managed to get 400mm and that piece of wood is a bridge yes, but it runs horizontally through 700mm of insulation, so not too much of a bridge.
    •  
      CommentAuthordjh
    • CommentTime1 day ago
     
    The usual answer to that situation is a bobtail truss. I don't understand the geometry in house49.jpg. At the front, it seems like there's a diagonal truss member, then a vertical strut, then a horizontal truss member, but somehow the two truss members still seem to be adjacent? And the truss behind has the components in a different order; what's going on there?
    • CommentAuthortony
    • CommentTime1 day ago
     
    To do with hip end and attic trusses http://www.tonyshouse.readinguk.org/icon/house46.JPG
    • CommentAuthorgravelld
    • CommentTime1 day ago
     
    Posted By: djhbobtail truss
    Thanks. I can see how that would lengthen the heat path.
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