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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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    • CommentAuthorItsBobbins
    • CommentTimeOct 14th 2018
     
    Hello,

    Im looking for further advice on how best to proceed with insulating a suspended timber floor.

    So far, the suggested have been:


    1) insulated slab

    we have around 500mm void beneath the floor. i understand we would need to build the level up with hardcore then something like sand > DPM > PIR insulation > concrete > Screed > finished floor?

    Would there be any issues with this method given the depth of the void?


    2) PIR insulation between joists

    The joists are only 50mm and most people suggest 100mm PIR. Could extra timbers be fixed to the joists at the counter batten points so allow for 100mm insulation?

    3) lay new flooring on top of existing flooring.



    Would there be much difference between options 1 & 2 in terms of heat retention? obviously there would be a difference in price!

    Would option 3 work be any good if new floor was laid with adhesive and sealed at the skirting boards?


    sorry i realise there are other threads in a similar vein!

    thanks in advance :bigsmile:
    •  
      CommentAuthordjh
    • CommentTimeOct 14th 2018
     
    Posted By: ItsBobbins1) insulated slab

    we have around 500mm void beneath the floor. i understand we would need to build the level up with hardcore then something like sand > DPM > PIR insulation > concrete > Screed > finished floor?

    Would there be any issues with this method given the depth of the void?

    The depth of the void is an advantage in many ways. It certainly means you could use EPS instead of PIR, saving some cash. The only thing you didn't mention is a narrow strip of insulation around the edge of the concrete & screed, and here something like PIR or phenolic would pay dividends (or even VIPs or aerogels if your pockets are deep).

    2) PIR insulation between joists

    The joists are only 50mm and most people suggest 100mm PIR. Could extra timbers be fixed to the joists at the counter batten points so allow for 100mm insulation?

    You could fix extra timbers underneath the joists to increase the depth of insulation. Or if you can get access from underneath, simply fasten 50-100 mm or so of insulation to the underside of the joists, thus covering the whole area.
    • CommentAuthortony
    • CommentTimeOct 14th 2018
     
    Fill the whole void with something insulating and non degradable, my choice would be platinum eps beads or if concrete eps sheets under a slab
    • CommentAuthorPetlyn
    • CommentTimeOct 15th 2018
     
    As per Tony's advice - an alternative to EPS is expanded glass bead insulation which doesn't degrade, decay or reduce in effectiveness, is inert and easily poured into small spaces. We have left-over material from our self-build and could send you a few to consider if this is of interest?
    • CommentAuthorItsBobbins
    • CommentTimeOct 15th 2018
     
    Thanks DJH and Tony. Food for thought.

    DHJ - are you suggesting i could fasten all of the boards to the underside of the joist? like this

    U U U U
    --------------------

    as i have around 50cm of space beneath the joist but no access hatch. I think it would be easier to batten then fit the insulation from above.


    Both - could the EPS beads present damp issues and would the beads be filled to finished floor level?


    Tony - given the choice would you go beads or slab?


    thanks again.
    • CommentAuthortony
    • CommentTimeOct 15th 2018
     
    Beads, I like the maximum amount of insulation
    • CommentAuthorbhommels
    • CommentTimeOct 16th 2018
     
    Option 1) it is for me. Next week our suspended wooden floor is going to get ripped out, the 370mm void filled up with EPS, and screeded over with UFH pipes embedded.

    I considered filling the void with beads, but I did not want to worry about dampness/humidity migration issues for the coming decades. There are a couple of joists that have become spongy due to condensation on a gas pipe entering the house, and probably also a dodgy soakaway. Addressing these means lifting the floorboards and replacing those joists anyway, so then we are halfway there already.
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