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Housing - Renovation: How to calculate improved energy efficiency using under floor insulation.

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  1.  
    Hi
    I am fitting a floating wood floor.
    The wood is approx 2cm thick & plus 0.7cm fiber underlay.
    I have standard floor boards which are old and don’t fit together too
    well at the moment. - just like normal 80yr+ floor boards !
    i.e. some have small gaps / holes where radiator pipes used to be.

    Would it be worth adding extra insulation under the floor boards before I fit the floor?
    The room is approx 20m2 with 2x10m external walls.

    How can I work out the energy saving?
    So I need to estimate a U value with the new floor?
    And a U value with the new floor + plus insulation
    To work out the energy savings so I can plumb that into current energy prices.
    I was looking into this insulation material but I’m open to suggestions.
    http://www.ybsinsulation.com/products_floor_foiltecdouble_calculations.htm
    The cavity is unfortunately just a little too small for someone to crawl underneath.

    Thanks

    Mike
    • CommentAuthortony
    • CommentTimeMay 17th 2009
     
    Yes, insulate under the floor now while the opportunity exists. quilt on strawberry netting -- search strawberry on here for more info
  3.  
    The "builders" tell me that its not worth doing. Hot air rises etc.
    Is there any information which shows energy saved?

    Thanks

    Mike
  4.  
    It's not that straightforward a calc as floors don't 'behave' quite as walls do, for example. Not least, hte heat-loss gradient is usually flatter. Hot migrates to cold, so forget that hot air rises. The saving is not staggering, but it is, in my view, not worth not doing.
    • CommentAuthorSaint
    • CommentTimeMay 19th 2009
     
    Mikeyb
    The builders say hot air rises, well that's true but we're talking about thermal transmittance. As a demonstration put a hot iron on his outstretched hand, once from underneath and then on top and see if he can detect any less pain from the latter.
    As Tony says stuff whatever insulation you can beneath the boards whilst the opportunity is there.
    As for the insulation in the link in your earlier posting, reading the technical bit where it refers to a 50mm foil wrapped airspace having virtually the same thermal performance as 50mm EPS and we're not even talking multifoils here....who are these people??
  6.  
    Thanks for your comments - much appreciated

    Mike
    • CommentAuthorralphd
    • CommentTimeMay 25th 2009
     
    I think RSI 1 is reasonable for upward heat flow:
    http://oak.arch.utas.edu.au/publications/PDF/R-values%20Part%204%20-%20Flooring.pdf
    RSI 2 likely approximates the downward heat transfer through 3/4" hardwood flooring, 3/4" subfloor on 2x10 joists and the airspace below the floor.

    From your description of the floor, I think it would have (without insulation) and R-value between RSI1.5 and 2.0.

    -Ralph
    • CommentAuthorSaint
    • CommentTimeMay 25th 2009 edited
     
    Ralphd for some reason I thought you were Canadian but it appears you're an Aussie? Maybe you'd like to explain the differnce in R values between where you are and the UK?

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