cathedral ceiling insulation

[botelj]

I am insulating my cathedral ceiling I will be using R38 but I can only find it in 4 foot lenghts where can i get it in bigger sections?

[Wgoodrich]

I suspect you will only find that high of R rating insulation in 4' lengths due to the thickness involved. Be aware you are not allowed to compress that fluffy insulation into an aread not big enough to take that thick of insulaton. Also be aware you are required a 1" air gap between that insulation and the bottom of the roof decking for air flow as required. An R 38 is very thick making it to require you to have a rafter and ceiling joist creating enough space to install that much insulation without compressing it.

Good Luck

Wg

[scuba_dave]

Are you using R38C for Cathedral ceilings?

R30C needs 2x10's
R38C needs 2x 12's

Regular R38 is 12", with an additional 1" air space to the decking you would need to nail wood to the bottom of the rafters for proper installation as WG said

http://www.owenscorning.com/around/insulation/project/cathedralceiling.asp

For proper ventialtion you should be putting in Rafter vents

http://www.owenscorning.com/around/ventilation/raftrmate_attic.asp

I'm using R30C on my cathedral ceiling then the R38 when it is flat
I haven't found it in anything except 4' sections, owens corning only lists it in 4' sections