Ceiling repair plus add spray foam insulation???

[wire10ga]

Hello all,
Been reading here for a while, but finally have a problem I need to bounce of the group.
I have a 92 Fleetwood double wide with a big hairy crack in the cathedral ceiling sheet rock due to the home not being level. Here is what I plan on doing during the repair of the ceiling so please poke any holes in my logic. After I get the home re-leveled of course.
Since I will have to pull down the sheet rock to repair I was also wanting to redo the insulation with spray foam to get a better seal and insulation R value as what is in there is just blown in and I'm sure has started to slide down to the outer walls. Reason for spray foam would be it would stay in place and seal out the outside air. What do you think? Would weight be a problem? Should I worry about ventilation? My thinking is no, since it would be more link a SIP panel that are being used on stick built homes. I think the rafters are only 2x4 but not 100% sure. Mainly want to redo insulation due to the ceiling always giving off heat in the summer and high energy bills.
Thanks!

[JD]

Hi CD and welcome to the forum.

In a 1992 Fleetwood, the first thing I would do is look for water damage at the top of the rafters, which I think will be 2x6. I think you will find that these units did not have roof ventilation from the factory. I have seen many of these homes where the space between rafters were totally closed off forcing the moisture vapors to collect at the marriage beam area.

I would not think that sprayed urethane insulation would be a problem but /i would check with a company that did that work to be sure. I would want to know how long this stuff "gasses" off and what it is that is gassing. You cold install roof venting, even with the spray insulation. There are foam channels you can install that would connect eave vents with ridge vents. I am not sure if a solid fill of this type of insulation would be recommended or not since I have never looked into it. But your SIPs panel analogy sounds right to me.

Just an opinion. I don't have facts.

[flcruising]

With the SIP example in mind...the problem with spray foam is it is applied to an open wall/ceiling then shaved flush with framing, so unless you rip off all the roof sheathing and spray it directly to the ceiling, you will have voids. Ventilation is still a must. Also, the roof trusses likely taper even with the vaults, so a 6" space at the eaves will be more like an 16" space a the centerline, this would be alot to fill and more weight compared to the blow-in.

If you have water issues, likely the insulation will need replacing in those areas, but I think you should re-evaluate your approach.

[wire10ga]

Currently there is no water links (knock on wood). So that is not an issue. The crack in the ceiling sheet rock was due to the house not being leved in the 19 years it been there.

I've been looking the web over and see where the foam is applied to the underside of the roof deck without ventilation. As for voids, I'm having to pull down the sheet rock in the kitchen to fix the crack in the ceiling anyway, so I can spray straight onto the underside of the roof deck without any issues, then replace the sheet rock and figure out how to make it look nice.

I would like to do this to the whole house, but think I will try it out on the section in the kitchen since I have to tear out it anyway. Since the roof pitch inside follows the roof pitch outside exactly, my thinking is I can turn the roof into a poor man's sip panel using a DIY spray foam kit. And unlike blown in insulation, it will stay put.

I've got to insulate my shed, so I will try this out on it first there to see how it will work.

[hisjr]

Sip homes usually do have a ventilation system built in them. If you're concerened about the air quality, you should seek consultation from a professional. I have a similar project planned for next spring on my mobile home. I'm going to use an energy exchange (heats or cools incoming air with outgoing air) and filtered ventilation system in the space where my furnace is now (installing radiant heating).

As for the roof, you should consult an insulation specialist. A vapor barrier may be required and you may be able to utilize reflecting material to maximize heating/cooling in the roof space.

[wire10ga]

Thanks for all the comments and suggestions