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U value questions regarding area weighted calculation.

Discussion in 'Building Regulations and Planning Permission' started by rssteve, 9 Jan 2017.

  1. rssteve


    3 Nov 2007
    Thanks Received:
    United Kingdom
    Hi, just in the process of sorting my building regs plans and need to work out what insulation i need to fit.

    I've got over 25% glass area so going to use the area weighted calculation to prove my design is no worse that the maximum if complying with part L.

    Q1. under part L does a bi fold door have to have a maximum of 1.8U, or is it classed as a window due to the glass and got to be 1.6 or under?

    Q2. When working out my area m2 of wall, floor etc, do I ignor the wall that joins the house I am building the extension onto, since that is going to be an internal wall?

    Q3. Do I class the wall that will attach the garage as an external wall? it is current single skin but will be knocked down and rebuilt as a cavity wall but will be internal to the garage on the other side, the garage is a simple single skin attached to the side of the house with a flat roof.

    thanks in advance.
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  3. wessex101


    4 Jul 2013
    Thanks Received:
    United Kingdom
    Off the top of my head, so could well be wrong.

    Q1. I always use 1.8 for sliding folding doors
    Q2. Yes, you only use external walls
    Q3. If the garage is unheated space I would take the wall between extension and garage as external wall.
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