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Replacing Rockwool with rigid board insulation in attic?

  • 20-08-2019 9:11am
    #1
    OfflerCrocGod
    Registered Users, Registered Users 2 Posts: 6,325 ✭✭✭


    We're going to convert our attic into a room and I was wondering if it made sense to replace the Rockwool (house is a new build, 2016, so it has 300mm of it on the floor) with another insulation such as rigid board? My thinking is that Rockwool isn't as good an insulation and that it degrades over time (not sure if that's still the case) so we may as well investigate replacing it now before we put a floor over it. Any opinions/recommendations?


Comments

  • #2
    Lumen
    Registered Users, Registered Users 2 Posts: 31,142 ✭✭✭✭Lumen


    How deep are the joists?


  • #3
    Dudda
    Registered Users, Registered Users 2 Posts: 1,541 ✭✭✭Dudda


    If you convert the attic then you want good insulation in the roof between the tiles/slates and the plasterboard of the attic room to keep the heat in. Rigid insulation is good for this. If this converted space is well insulated then the insulation you want between the downstairs and the new attic room is acoustic insulation rather than insulation that helps with heat. Therefore Rockwool would be better.

    Other factors I'm not dealing with are strength of joists, fire escape, access, room height, planning permission, etc and other building regulations.


  • #4
    OfflerCrocGod
    Registered Users, Registered Users 2 Posts: 6,325 ✭✭✭OfflerCrocGod


    Lumen wrote: »
    How deep are the joists?
    I'm not sure but they are buried below the insulation so I'd say 100mm. I was wondering if another advantage to replacing Rockwool would be that the new attic floor could be closer to the joists, or is that fixed by the RSJ and the attachments for the new floor joists?


  • #5
    OfflerCrocGod
    Registered Users, Registered Users 2 Posts: 6,325 ✭✭✭OfflerCrocGod


    Dudda wrote: »
    If you convert the attic then you want good insulation in the roof between the tiles/slates and the plasterboard of the attic room to keep the heat in. Rigid insulation is good for this. If this converted space is well insulated then the insulation you want between the downstairs and the new attic room is acoustic insulation rather than insulation that helps with heat. Therefore Rockwool would be better.

    Other factors I'm not dealing with are strength of joists, fire escape, access, room height, planning permission, etc and other building regulations.
    Yes I'm sure we'll be getting rigid board insulation in the rafters. I figured good insulation in the attic floor would still help reduce/slow overall house heat loss though.


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