Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Combining u values

Options
  • 19-03-2009 11:09am
    #1
    Registered Users Posts: 40


    Would appreciate any advice combining u values of building elements.
    For example : calculating together the value of a 325mm solid masonary wall with 52.5 mm overall Kingspan Therma board drylining.
    Default for a circa 1940 construction is 1.6 u value but from the table of contents on standard building materials thermal conductivity using stated TC's does not equate to a 1.64 default value.
    The method I employed was to work in reverse to determine a T.C.
    0.325 / 0.52 = T.R of 0.625 1 / 0.625 = 1.6 u value (of 325mm masonary wall)

    Taking the thermal resistance of the above with for example, the T.R of 52.5mm Therma board @ 1.80 equates to an overall u value of 0.41

    0.625 (tr) + 1.80 (tr) = 2.425..... 1 / 2.425 = 0.41 overall u value.

    Anyone have a better way ? or indeed is my equasion even correct before I employ theese calculations.

    Regards
    Legs.


Comments

  • Registered Users Posts: 2,489 ✭✭✭No6


    Use a U Value Calculator legs. Use the resistance for stone (not the DEAP default u Value)with all the other relevant restistances for an accurate U value of the construction. (assuming of course that you have proof of the drylining etc!!)


  • Subscribers Posts: 41,586 ✭✭✭✭sydthebeat


    if you are calculating u values you MUST refer to this document.

    http://www.bre.co.uk/filelibrary/rpts/uvalue/BR_443_(2006_Edition).pdf

    always be aware of air space resistance and thermal bridges.

    Its extremely difficult to assess existing construction without a large invasive survey.


Advertisement