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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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    • CommentAuthorcczmark
    • CommentTimeSep 20th 2018
     
    Hello,

    We have a 30's house with un-insulated sloping eaves as per the detail below (not identical but pretty close) and photo. Seems to me there are 3 options to insulate.

    1 - Remove plasterboard and insulate from underneath (i.e inside rooms) - Not doing this as way too much disruption and mess
    2 - Remove tiles and insulate from above - requires scaffold, possibly difficult?
    3 - Insulate from inside attic - some constrained access, generally unpleasant work and difficult to tell if there is no gap at the bottom (defeats the object..). See photos.

    Ideally I'd like to do 3. Any suggestions - methods, materials, tips, etc. Is spray foam an option (DIY or professional)? How to maintain ventilation (plastic eaves ventilators)?

    This may have to be a DIY job as my contractor has quoted a stupid price :-(

    Thanks,
    Mark.
      roof eaves insulate.JPG
    • CommentAuthorcczmark
    • CommentTimeSep 20th 2018
     
    Photo...
      eaves2.JPG
    • CommentAuthorgravelld
    • CommentTimeSep 20th 2018
     
    I have faced similar issues and I think the best answer is (2). Why do you think it is hard?

    How long is the sloping part?
  1.  
    You can do a better job with (1), and comply with the Regs, too.
    • CommentAuthorcczmark
    • CommentTimeSep 20th 2018
     
    2 is not something I've done before (remove & replace tiles), but assuming the access is OK it looks straightforward enough having watched a youtube video.

    Sloping part is slightly less than 1m
    • CommentAuthorcczmark
    • CommentTimeSep 20th 2018 edited
     
    Posted By: Nick ParsonsYou can do a better job with (1), and comply with the Regs, too.
    Sorry too much mess - can't face that!
  2.  
    Oh, go on - please!

    Are those 100 x 50 rafters? If so, you can only get 50mm insulation if you leave the correct 50mm vent gap. You'd need 125mm Pu to get 0.18W/m2K as per regs, so 50mm between, 75mm below, 25x50 battens and plasterboard. Job's a good'un!
    • CommentAuthorgravelld
    • CommentTimeSep 20th 2018
     
    What I didn't say is that I think (2) AND (1) is the best way to go but I thought you REALLY didn't want to hear that!

    Have you considered a future air tightness layer, and how you could build that in, even if gradually?

    You also have to consider things like vapour control there.
  3.  
    I did 3, feeding artfully crafted slices of kingspan in from above so they locked together and filled the space tight against the rafters. Each rafter space needed at least two pieces to get them in past the ends of the ceiling joists.

    If I did it again i'd do 1 as shaping insulation in a tight space is a slow messy job. As has been mentioned you get much better results working from below and you can use big rectangular pieces.

    Either way it makes a big improvement, so go for it!
    • CommentAuthorbhommels
    • CommentTimeSep 21st 2018
     
    Facing exactly (and I mean exactly) the same thing here and it looks I should mentally prepare for 1.... And we had the ceilings plastered only 5 years ago :-(
  4.  
    cczmark - looking at the photos, it looks like the tile battens are on edge and there is no roofing felt (are those tile nibs I see?) - is this really the case?

    If there is no roofing felt then I would install some before insulating.

    If you have felt then depending upon the type (breathable needed) you could blow in cellulose insulation, either DIY or professional.
    • CommentAuthorgravelld
    • CommentTimeSep 22nd 2018
     
    Is it really possible to get as good an insulation installation between the rafters from below as it is above? I mean: insulation touching all planes, no gaps once the p/board has gone back up, hopefully not pushing away any insulation.

    Whichever way you approach it you have to consider the air barrier and in many cases access from above/outside will be required to keep this continuous.
  5.  
    I've seen it done well, and badly, both ways, but many 'from above' installations, which roofer have to do to meet the Regs, only fit where they touch, and they don't!
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