Cavity wall to vaulted ceiling insulation

[matlob]

Hi

I have a cavity wall with full insulation going into a vaulted ceiling.

Should I close the cavity somehow or just continue the insulation out of the cavity wall. The eaves are vented so not sure what best practise is.

Thanks for any help.

 

[noseall]

Hi

I have a cavity wall with full insulation going into a vaulted ceiling.

Should I close the cavity somehow or just continue the insulation out of the cavity wall. The eaves are vented so not sure what best practise is.

Thanks for any help.

View attachment 322531

Let the cavity batts butt against the vaulted insulation, i.e. - - continuous. Try and get the PIR as low down as you can, even if that means cutting the end at a jaunty angle.

 

[matlob]

thanks! will give that a go

 

[noseall]

thanks! will give that a go

You often need to do the jaunty angle bits first (top and bottom) with smaller individual pieces, as you wont be able to fit the PIR into two opposing cervices, with one large piece. Faffy, I know.

 

[robinbanks]

The eaves are vented

They won't be (shouldn't be) when you're done. If they are you might as well stand the PIR up in the garden for all the good it will do

You often need to do the jaunty angle bits first (top and bottom)

Often find it easier to insulate the lower zone with wool/batts than PIR. Easier to get tucked into nooks and crannies to kill air movement than fannying around with expanding foam. PIR performs better (lambda) in theory, but if air is blowing around it it's easy to end up worse than wool

 

[noseall]

They won't be (shouldn't be) when you're done. If they are you might as well stand the PIR up in the garden for all the good it will do

Cold (insulation detail) vaulted roofs, have to have the airspace above the PIR (usually 25-50mm ai-gap), vented from bottom to top. We usually do this via OFV's and vented dry ridge.