Delaware code for a fully conditioned sunroom ceiling?

[spanpris]

Hello all,
I‘ve been having a heck of a time with an addition I added to my existing home. It’s approximately 400sq ft, conditioned, has a split system for heating/cooling and is separated from the main house by interior glass French doors. I’ve already had to fight the GC to get a vapor barrier installed below the sunroom, to the point of having the county building inspector involved. Now I’m wondering about the ceiling. We went with a cathedral ceiling with nickel gap(think shiplap if you aren’t familiar) finish. The “craftsmanship“ on the nickel gap was horrible. Work is being done to correct the finish and in the process some of the boards were removed. I can see that the insulation is R21(different from the contract) and that there is no barrier of any type between the boards and insulation. I’ve been told that the R value should be at least 38 and that there should be some form of thermal barrier. Does anyone know where I can find code that would address this situation?
Thanks!

 

[Msradell]

You already stated that the insulation is different than the contract, that alone should be enough to call him out on it! Is there anything in the contract about a barrier between the boards and the insulation?

 

[spanpris]

If he had written the contract correctly to begin with that might have been possible. I’ve read there is no way to fit R49 in a cathedral ceiling. No mention of a barrier, something I am learning after the fact might be needed.

 

[Msradell]

If he had written the contract correctly to begin with that might have been possible. I’ve read there is no way to fit R49 in a cathedral ceiling. No mention of a barrier, something I am learning after the fact might be needed.

Being able to fit R49 insulation in a cathedral ceiling is certainly not impossible. It depends on the site of the rafters in the type of insulation used! If the rafters are 2x6 or larger it's certainly possible.

 

[Mr. Inspector]

Don't they inspect insulation in Delaware?

 

[Paul Sweet]

"If the rafters are 2x6 or larger it's certainly possible."

Only with aerogel. Polyiso would require 2 x 10s. Fiberglass would require 2 x 16s. That only allows a 1/2" or so airspace above the insulation. If you want the recommended 2" you have to go to the next size rafter.