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U Value Adjustment for Porch

  • 28-04-2009 07:00PM
    #1
    engrish?
    Registered Users, Registered Users 2 Posts: 911 ✭✭✭


    Which is not big enough to be a draught lobby....


    What is the adjustment factor I use? Inside the porch is a wooden door and a large single glazed side window, what adjustment do I make to the side window?

    The sliding door into the porch is single glazed aluminium, the porch is .87m and then you have a wooden door and a large side window.

    Thanks,

    Engrish


Comments

  • #2
    engrish?
    Registered Users, Registered Users 2 Posts: 911 ✭✭✭engrish?


    engrish? wrote: »
    Which is not big enough to be a draught lobby....


    What is the adjustment factor I use? Inside the porch is a wooden door and a large single glazed side window, what adjustment do I make to the side window?

    The sliding door into the porch is single glazed aluminium, the porch is .87m and then you have a wooden door and a large side window.

    Thanks,

    Engrish

    Anyone done something like this? Seems like it should be obvious but I am stuck on it.

    I know what to do with the door but as the window is so big I don't think I should include it as part of the door. But if I am to put in a different uvalue for it DEAP says I need written back up for the adjustments...


  • #3
    recedite
    Closed Accounts Posts: 13,992 ✭✭✭✭recedite


    Its a very common occurence in existing dwellings, yet not mentioned in the training.
    I have used two methods;
    The first is to apply the Ru formula using 0.25 as per "conservatory in a recess" because these porches are normally recessed into the building.
    Apply it to both the door and the window separately.Strictly speaking you would also apply it to the sidewalls too and here the whole thing becomes more trouble than it is worth, hence method 2;

    Ignore the inner door and treat the new outer sliding door as the new periphery of the heated space.It will have as good a U-Value on its own without the previous Ru adjustment because it will be double glazed.

    Either way will make almost no difference to the BER result.
    I would be interested to hear what others do.


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