Drywall over foam board?

[Unregistered]

Replacing plaster on slope ceiling, 150year old farm house. The plaster had loosened to the point of falling off in areas. It was obvious many repairs have been made over the years. Took the plaster off on the entire slope area and left the wood lathe. The area to refinish with drywall is approximately 5 1/2 ft (slope) by 12 ft. wide. The slopes had been blown in in the past. I want to upgrade the insulation in the slope, prior to installing the drywall. I plan on leaving the blown in behind the lathe and adding a poly vapor barrier and then a rigid foam board.

Question: My plan is to install up to a 1" rigid board over a poly vapor barrier. Tape the foam board joints (duct tape) and stagger the joint with the drywall directly over the foam. I plan on using the appropriate length screws for the drywall, to compensate for whatever foam board i go with. Will the rigid foam provide enough stability to keep the drywall joints from cracking over time?

Thanks ahead of time.

[Wgoodrich]

This being an existing building being remodeled often times the inspector will make best with what you have available. However if you wish to upgrade this to current code while you have this ceiling open we really need your state and preferably you county you come from so we can identify your zone. Average insulation required for ceilings is R30 yet this changes depending on the zone you are in. Once we know the zone you are in then we can better help you with your options getting best you can with what you have or what is probably best design in approach.

Curious

Wg