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
Hi there,
There is an issue with role permissions that is being worked on at the moment.
If you are having trouble with access or permissions on regional forums please post here to get access: https://www.boards.ie/discussion/2058365403/you-do-not-have-permission-for-that#latest

mixing insulation types for cold roof construction

  • 07-11-2010 12:01pm
    #1
    Wavehopper
    Registered Users, Registered Users 2 Posts: 46 ✭


    Hi all,
    I've read a few threads on this forum advising people not to mix quilt and PIR board insulation in the attic but is it ok to use both these insulation types independently in different parts of the attic?

    I'll have cold roof construction with insulation on the flat but I also wanted to floor centre part of attic for storage. However I didn't want to loose the head-room with 400mm quilt and the hassle that goes with this in terms of timber support for sheeting.

    I didn't want to insulate on the slope either as I didn't want to heat a large attic space that won't be a living space and I don't have any tanks/pipes in the attic either. I also thought that insulating on flat would be cheaper than insulating on the slope at this stage.

    Areas that I'm not flooring:
    Skim finish
    Foilback plasterboard
    Air-tight membrane (will be sealed down to walls with scratch coat)
    200mm Knauf quilt in-between 6"x2" joists
    200mm Knauf quilt over this running perpendicular to lower quilt

    Areas that I'm flooring for storage:
    Skim finish
    Foilback plasterboard
    Air-tight membrane (will be sealed to walls with scratch coat)
    150mm PIR board in-between 6"x2" joists
    2"x2" counter-battens on top of joists to give 50mm air-gap
    18mm ply sheeting

    Firstly, is there any issue doing it like this?
    Would 150mm Xtratherm (or similar) give me similar performance as 400mm quilt?
    Would I gain anything by having insulated plasterboard on ceiling or would this not give the same insulation coverage since it's individual per room and doesn't cover internal block walls?

    Any comments or advice would be much appreciated.

    Thanks.


Advertisement