Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



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.

Buy individually or both books together. Delivery is free!


widget @ surfing-waves.com




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthornstansbury
    • CommentTimeNov 23rd 2017
     
    The next step in our retro fit journey is to insulate our roof..

    Currently we have a 1969 metal clad roof about 4 degree incline - zero loft space, basically about 250mm between the ceiling plasterboard and the cladding with about 20mm polystyrene "insulation" loosely fitted above the plasterboard

    Whilst the roof will almost certainly get replaced in the next 5 years or so, I'd like to build an airtight insulated seal internally now, but without lowering the ceiling levels any more.

    Currently, I'm thinking of 100mm EWI graphite EPS insulation foam sealed between the rafters with an airtight membrane across the ceiling which is taped to the parge coat on the walls, before the plasterboard goes back on top.

    This is a pretty big investment both in terms of time, effort & money and wondered about all your thoughts?

    I guess gotchas doing this - especially failing in the airtightness approach, and thermal bridging by only insulating between rafters, but also being pragmatic and just waiting a for a few years to insulate/seal from above when the roof gets replaced? I am more than happy to do the work, I just want to make sure I'm maximising my effort.

    To be frank, from my experience with the UK building industry thus far, I have more faith in my attention to detail in air-tight sealing below rafters than the roofers might above - but I would really appreciate your thoughts here.

    Cheers,

    Neil
    • CommentAuthortony
    • CommentTimeNov 24th 2017
     
    If you do it then it should comply with current regs, part L1b
    • CommentAuthorJeff B
    • CommentTimeNov 24th 2017
     
    I'm not an expert on Part L1b (there will be others who are and will doubtless be on here soon to advise you better than me) but I would take the pragmatic approach and say do what you can. At the moment it looks like you have almost zero insulation in the roof space, especially as you say the polystyrene is loosely fitted. Short of lowering the ceiling I think what you propose is a good compromise; not a "nice" job, I don't envy you! After insulating between the rafters I would be tempted to fix 25 x 50mm battens across the rafters then put an extra 25mm of PUR insulation between the battens. Then fasten the new plasterboard onto the battens. I know this will lower the ceiling but I wouldn't think 25mm is a big deal?
    •  
      CommentAuthordjh
    • CommentTimeNov 24th 2017
     
    Posted By: nstansburyCurrently we have a 1969 metal clad roof about 4 degree incline - zero loft space, basically about 250mm between the ceiling plasterboard and the cladding with about 20mm polystyrene "insulation" loosely fitted above the plasterboard

    Whilst the roof will almost certainly get replaced in the next 5 years or so, I'd like to build an airtight insulated seal internally now, but without lowering the ceiling levels any more.

    That's a very shallow roof slope. What's underneath the metal?

    What do you plan to do when you replace the roof? What's appropriate now might not be when you do replace it.

    If it was me, I think I'd be planning just to do the job once and concentrate on bringing that date forward as much as you can.
    • CommentAuthorowlman
    • CommentTimeNov 24th 2017
     
    I think Dave's right.
    Admittedly I have no idea what the current house is like but IMO you need to seriously fast forward and firm up your eventual plans for the house/roof BEFORE you start any cocooning of the present structure. Working backwards from that future ideal with a less ambitious plan now may help and save you much time and money. Accept that in the short term it won't be perfect and then plan to bring forward your new roof? plans ASAP.
    • CommentAuthornstansbury
    • CommentTimeNov 25th 2017
     
    Hmm ok thanks for all your thoughts - interesting...

    We're the end of a terrace of 4 townhouses (in a conservation area for part L1B), and the roofs are constructed in pairs, with each end-of-terrace connected to the neighbour.

    Although our roof is currently sound, it has been suggested all 4 of us replace our roofs, and raise them by 100mm to insulate over rafter before replacing the metal cladding, with a new zinc type roof (if we can all afford that!).

    The challenge is two fold:

    a) At the very least our roof will need to be replaced with our immediate neighbours, and having just been partly responsible for a terrace wide replacement of all our windows, I'm not sure how much immediate desire there is for another £20k each on a new roof.

    b) Our house is back to a shell internally, and aside from the fact it is freezing atm, I have the opportunity to do any internal works I want, IWI is one thing going up and so figured a robust, airtight internal roofing detail sealed with the IWI whilst I have the opportunity made sense. If the 100mm over-rafter happens with a roof replacement too then that's a bonus.

    @djh - to the best of my knowledge it appears to be just a type of roofing felt, I'm not sure exactly the material. I'll go and have a dig around to check.


    The consensus so far from you guys seems to be don't focus too much on insulating/sealing it internally? Is it that much easier & more cost effective to seal with the roof off?


    Thanks for all your thoughts
      front-elevation.png
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press