Insulating pitched attic ceiling

[pattison87]

Hello,
Currently insulating my attic which is used as 2 bedrooms. Have used rockwool on the horizontal part and just moving on to the pitched sections. Plan is to use 25 mm pir boards between rafters (50mm air gap) and then 50 mm fixed across this below the rafters with 12.5 plasterboard on top. Will this be sufficient? I can not afford to loose anymore headroom.
Also do the boards need to be foil faced on all sides or just the external faces? Just wondered as I will have 2 boards butting up to each other and is cheaper to buy foil/ tissue boards than foil/ foil.
Thanks in advance
Chris

 

[limerockconstruction]

Sufficient for what? It will certainly improve your current situation, but is it sufficient to meet regs? Then no.

If it isn't being regulated, then go 50mm between leaving a 25mm air gap and tri-iso the underside. You must have a tiny space if you cant afford to loose another few mm's in headroom.

 

[pattison87]

No doesn't need to meet regs, they are existing bedrooms. They are good sized rooms just don't want to keep eating in to the head room. Don't particularly like the look of the tri iso stuff. Would 50mm between and 25mm below be ok then with a 20-25mm air gap?

 

[noseall]

No doesn't need to meet regs, they are existing bedrooms. They are good sized rooms just don't want to keep eating in to the head room. Don't particularly like the look of the tri iso stuff. Would 50mm between and 25mm below be ok then with a 20-25mm air gap?

As said, ok for what.

Will it be an improvement - yes.

Will it be better than nowt - yes.

Is it likely to be enough to prevent the problems associated with inadequate insulation - mebbe/mebbe not.

Why should the fact that they are existing bedrooms make them exempt from building reg's?

 

[limerockconstruction]

WHy don't you like the look of tri iso?