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air tightess - how to PREDICT performance in advance ?

  • 26-05-2008 8:42am
    #1
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭


    Is anyone aware of a method to fix a required level of air tightness other by performance specification

    i.e. one may specify " Q50 5 ac/ hr" - but in terms of a materials/construction specification - what does one do ?

    Take an analogy with "external wall to achieve 0.25 Wm2 K U value"
    We have a methodology to to "play" with different wall construction types and can engineer different material layers and thickness to achieve precisely 0.25 . We can then adjust material thickness to answer a query like- "what if we want to improve the wall to 0.22 Wm2 K "

    Is there a method to calculate air tightness levels like this ?


Comments

  • #2
    Slig
    Registered Users, Registered Users 2 Posts: 1,550 ✭✭✭Slig


    I dont know of any building products that quantify air permiability, the only real way to specify (that I can think of) is through vents.


  • #3
    sydthebeat
    Subscribers Posts: 42,172 ✭✭✭✭sydthebeat


    i think this almost impossible because the factor that would have to be assumed to be constant would in fact b ethe most variable.. ie Workmanship.

    perhaps it would be possibly with prefabricated systems, that are constantly assessed by blower door tests, but 'open systems' such as cavity wall depend so much on workmanship that an 'air tightness calculator' would be impossible.

    perhap swhen these blower door tests become very popular it will be possible to compile an analysis of different systems and compare their average air tightness results.


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