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Roof insulation, using attic and airtightness

  • 30-06-2011 10:24pm
    #1
    Troy McClure
    Registered Users, Registered Users 2 Posts: 309 ✭✭


    After looking at various insulations I think we are going to go with 300 mil wool insulation. I figured we could use attic for storage but builder says this would require cross rafters and more insulation in order to put in a floor. We are having a HRVS which most seem to put in the attic. This would require a trap door. Add to this the installation of an airtight membrane. How can you have an effective airtight membrane with a trapdoor?. Do people use airtight trapdoors? (sounds expensive).
    I dont like the idea of having HRVS in cold space as I have been advised against it. Is there a choice.? The house inside would struggle to house it.
    The house is 1.5 story and building a warm roof in a small roof space seems problematic especially with airtight membrane installation not to mention the espense of it.
    Anyone come across such issues before?


Comments

  • #2
    sydthebeat
    Subscribers Posts: 42,569 ✭✭✭✭sydthebeat


    the solution to your problem is to construct your roof in a "warm roof" type method. Here you insulate between and over the rafters. You can use a woodfibre type insulation product over the rafters.
    this means that you can house the HRV ini the attic void which is till a 'warm' space. It means you do not need to leave a ventilation gap within your rafter space so you can full fill it. The woodfibre adds greatly to your air tightness strategy.


  • #3
    Troy McClure
    Registered Users, Registered Users 2 Posts: 309 ✭✭Troy McClure


    HOw is this done? Builder says to come across the flat roof and up inside the supporting timber joists. Reckons it would be very difficult to do warm roof completely on angled roof only.


  • #4
    sydthebeat
    Subscribers Posts: 42,569 ✭✭✭✭sydthebeat


    Troy McClure wrote: »
    HOw is this done? Builder says to come across the flat roof and up inside the supporting timber joists. Reckons it would be very difficult to do warm roof completely on angled roof only.

    its not.. google "gutex" or softboard.. and see some details


  • #5
    galwaytt
    Registered Users, Registered Users 2 Posts: 12,747 ✭✭✭✭galwaytt


    Troy McClure wrote: »
    .......The house is 1.5 story and building a warm roof in a small roof space seems problematic especially with airtight membrane installation not to mention the espense of it.
    Anyone come across such issues before?
    Troy McClure wrote: »
    HOw is this done? Builder says to come across the flat roof and up inside the supporting timber joists. Reckons it would be very difficult to do warm roof completely on angled roof only.

    What stage is the roof at now ? Builder is struggling because he's only thinking in terms of std cut roof construction.

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  • #6
    Troy McClure
    Registered Users, Registered Users 2 Posts: 309 ✭✭Troy McClure


    Building is starting in a months time, so roof is at no stage yet. In fairness builder is working with a budget also.


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  • #7
    DanWall
    Registered Users, Registered Users 2 Posts: 509 ✭✭✭DanWall


    What is a HRVS?


  • #8
    sydthebeat
    Subscribers Posts: 42,569 ✭✭✭✭sydthebeat


    Heat Recovery Ventilation System


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