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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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Products: retrofitting internal insulation to existing wooden roof

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    • CommentAuthorJean
    • CommentTimeJul 23rd 2009
     
    Hi
    We have a single story extension (1991) with a pitched roof lined with wood and with the rafters exposed. Can anyone recommend a suitable, thermally efficient, insulation material that can be fitted between the rafters to a depth of 4cms ( to allow the rafters to remain exposed) . Ideally the product used can be just painted without plastering it first!
    thanks,
    Jean
    • CommentAuthorCWatters
    • CommentTimeJul 23rd 2009 edited
     
    I believe insulating the roof needs Building Control Approval and that means the end result would need to achieve specific U-Values. Is there any insulation in the roof already? Can the timber lining be easily taken down? Is it between or on top of the rafters?

    What sort of membrane was used under the tiles? If it's a vapour permeable membrane it might be possible to avoid the need for a ventilated cavity under it, thereby providing more depth for insulation.

    What is the overall depth of the rafters (including the bit hidden by the timber) and how much rafter do you want to retain exposed?

    Depending on the answers to the above you might be able to install Celotex/kingspan or may have to look at something more exotic such as..

    http://www.spacetherm.com/

    which I believe comes as an Aerogel/plasterboard laminate...but even that can't work miracles.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 23rd 2009
     
    New kid on the block http://www.enigma-insulations.co.uk/tlxrafterfit.html - what does the team think?
    • CommentAuthorCWatters
    • CommentTimeJul 23rd 2009
     
    The examples they give include 40 to 70mm PIR foam under the rafters to achieve the U-Values. Otherwise looks ok. Easier to install than two layers of PIR foam.

    I'm not sure I like their proposal for use with UFH in floors. There appears to be large air gaps around the pipes which are free to move?

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