Iffn you can afford it, DO It!!

I will find that out in the next couple days. I have a bid coming.

Yeah, I agree, it is real efficient...just giving you my experience, may depend on size too, my house is 30x66 I put plastic down (can't remember mil value), and 2" underfoam. Don't let my account turn you off, some good insight on here!

Yukon John, I appreciate all the feed back on it. I am only doing a 24x32 building with a 8 foot side wall. 1 36 door and a 72 door. 8 windows 4@ 36x54 3 @36x43 and a 30x36

I think you'll be fine, is your floor done? That is the biggest thing, don't sweat it, spray foam is awesome, just make sure it's done right. For a shed, if you can afford it,you'll be golden! If you do it, do it ALL (walls, and roof), you'll be sorry if you don't!

sounds like you did everything right, what a mystery.

Sounds like you sealed your house really tight and it needs a heat recovery system to bring in fresh air and exhaust some air. I would suggest you check the Carbon Dioxide level in your house it can create a seriously dangers level on houses that are so tight and have no ventilation system to exhaust stale air and bring in fresh air. I have checked a number of high efficiency houses and found really high levels of Carbon Dioxide .

dry surface of at least 40 degrees,3" on walls 5" on roof.....if you have a ceiling you can blow fiberglass on top of it to save a little $$

It'll be spendy!

Personally, I'd spray the walls and finish the lid than blow in fiberglass in the attic.

This is what a buddy of mine that puts up pole barns says. He says if you spray the entire thing its going to sweat. I just hated to spend extra money on insulation to make it sweat. I have no idea, that's why I am asking.

One way we used to do it was to put hi density 4x8 styrofoam panels on the ceiling stringers from the room side, then put blow or roll in insulation in the attic area above. You can put longer nails thru your interior finish ceiling wood, or longer screws thru the Sheetrock if that’s what you use to finish the lid.
As for sweating, you need to keep the air circulating and replenishing from the outside. No big deal. The room just has to breath. Healthier for you too.

Osky

I've been involved in several buildings where everything from the crawl space to the ridge was sprayed. I have never heard a complaint about sweating or anything else for that matter.......other than the initial cost.

As far as additional cost to spray the roof goes, Once the contractor is set up and the material is onsite, the additional square footage wouldn't add much cost relative to the potential benefits. Remember, you want the highest R value possible in the attic/roof cavity. More important there than in the walls .

One thing you can do to reduce the cost is to frame the ceiling and spray inside the ceiling joists. You need to cover the tops of those joists to provide a surface for the spray to adhere to, but it may reduce the material quantity by a small amount. Depending on the roof pitch, you will have somewhat less square footage to spray into a flat ceiling than you would spraying the underside of the roof.

I have done that before and used cardboard baffles between the bottom cords of the trusses as a backing for the foam. The only problem there is your insulation thickness is limited by the depth of that framing member. We added blown in cellulose on top of the foam.