insulating cathedral ceilings

[2cool2hear]

How would you insulate your cathedral ceiling? Rafts are 10-12 inches deep.

And if you have your house insulated and how do you like it? What would you have done differently?

 

[Simeon]

What's the roofing material?

 

[sands35]

Read this:

http://www.buildingscience.com/docu...6-complex-three-dimensional-air-flow-networks

and

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling

I'm going through the same thing to figure out how to insulate a currently un-insulated cathedral ceiling with a bad ice-damming problem.

Summary:
NO recessed lights or ways to create air infiltration.
Eliminate all air infiltration into the insulation pack.
Snow load dependent - put on a cold roof to keep the roof deck below freezing with a snow load.

Code is to insulate to R49 (zone dependent).

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm

 

[southernfriedcj]

How would you insulate your cathedral ceiling? Rafts are 10-12 inches deep.

And if you have your house insulated and how do you like it? What would you have done differently?

Current house(in GA): R19 batts and 2" Dow board under drywall. I like it.

New house(in GA): 4" closed cell foam(R25 or so) and 2" Dow board under drywall. I hope I like it more.

In the areas with an attic it will be just closed cell foam, no Dow board.

I will also have a silver Galvalum metal roof.

I'm going for comfort. Energy savings will be a plus. I'm not concerned with "payback", although it shouldn't be too bad.

 

[willymakeit]

In theory you need a ventilation area between the insulation and roof deck.
We used to install 10'' fiberglass batts in 12'' space to achieve this. Your local codes may require a higher R value which can be achieved with strapping and ridged foam. means and methods seem to be changing frequently anymore.

 

[Randy in Maine]

I used high density spray foam in my unvented cathedral ceiling (in my 1968 log house), but I only had 2x6s to work with, so about 5 1/2" is all I have. If I had 2x10s, I would have sprayed all 9".

Actually though I am pretty pleased. I have radiant floor heat and the ceiling is actually a little cooler than the floor 60º/65º. Very tight and no ice dams.

 

[yeldogt]

Spray foam closed sell -- every house the last 20 years.

I don't do ventilated roofs