Rockwool Between rafters?

eamon11

hello folks,

I need insulation for the roof between the rafters. Its expensive but I see rockwool is slightly cheaper and states that its suitable for roofs.
But is rockwool stiff/rigid or is it like earthwool? The reason I am concerned with earthwool for between the rafters is that is might sag or pull over time? There will be plasterboard nailed on the rafters so the insulation will be sitting on the plasterboard but still it will be at a slant.

Opinions appreciated.

Thank you

TheLastMohican

eamon11 wrote: »

hello folks,

I need insulation for the roof between the rafters. Its expensive but I see rockwool is slightly cheaper and states that its suitable for roofs.
But is rockwool stiff/rigid or is it like earthwool? The reason I am concerned with earthwool for between the rafters is that is might sag or pull over time? There will be plasterboard nailed on the rafters so the insulation will be sitting on the plasterboard but still it will be at a slant.

Opinions appreciated.

Thank you

Time warp Eamon?

Air current is imperative, so you need a baffle or such like.

Calahonda52

https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx
whats the roof buildup: old sarking felt?

eamon11

Thanks Calahonda,

all new roof with 6 inch rafters. There are also a few old rafters of 5 inch in the old section. All new breathable felt, laths and slates.

Is rockwool a rigid board?

Dtp1979

eamon11 wrote: »

Thanks Calahonda,

all new roof with 6 inch rafters. There are also a few old rafters of 5 inch in the old section. All new breathable felt, laths and slates.

Is rockwool a rigid board?

No it's not rigid.