Insulating 40 x76 x 12 pole building

[MNBobcat]

Hi Everyone,

I saw there was a similar topic to this one posted but I didn't want to hijack the topic by asking my questions there. I have a slightly different direction on my building.

I have trusses 4 feet on center. I originally was going to install my metal ceiling directly to the bottom of the trusses with no vapor barrier. I was then going to have (I believe it was 1 or 2 inches) of foam sprayed over the top of the ceiling and then cellulose blown in on top of that. The foam provided the vapor barrier and a tight seal. They were then going to spray 3 inches (R19) of foam on the walls. I was going to fur out the walls and install OSB to finish.

Well, the above came in at about $11K. I talked to another spray foam company and they recommended not foaming the ceiling. They said they only foam the ceiling when the metal is already up and there is no vapor barrier. Because my metal wasn't up, they recommended installing a 4 mil vapor barrier, hanging the metal ceiling and then blowing in cellulose. On the walls they were going to put rigid foam as a backer at the top of the wall cavity and then spray 3 inches of foam directly on the inside of the metal walls. This came in at $8K. So not foaming the ceiling would save about $3k.

I live in Minnesota where it gets colder then heck. The pole building will be a big workshop. I have a wood boiler and I was going to hang a heat exchanger at each end of the building.

My goal is to have the building really well insulated so that I go through less wood. Of the 2 plans above, what do you guys think of the second plan? It sure seems sound to me and I like the cost savings.

Anyone ever done it like the above and were you happy with it?

Thanks!

 

[LD1]

SO if I understand, NOT foaming the ceiling saves 3k on the foam bill.


But how much is it going to cost you for 4mil barrier + blown in insulation.

Because the actual savings ISNT going to be 3k, rather the difference of these two.

 

[MotorSeven]

If this is a shop why the ceiling? I am a big fan of the spray on stuff and have it directly on the backside of the metal on my Quonset Hut....no ceiling, or rather the foam is the ceiling. I painted it white, so it looks like a Polar Cave.

 

[KennyG]

If I understand, there is a 3K savings including the cost of the cellulose. I would go with the poly/cellulose. It's a real common approach and it's quick and easy. I know some people like spraying foam on the bottom of the roof metal, but I've never been comfortable with that. It gives you that much more space to heat (with hot air that rises, while you are down on the floor) and takes away the ventilation path along the bottom of the roof metal through the ridge vent.

 

[MNBobcat]

The first guy was going to spray an inch or two of foam on the back side of the ceiling and then put down cellulose on top of the foam. In that case, the foam makes the vapor barrier and bonds all of the metal and trusses together.


The second guy said to put up a vapor barrier and then the cellulose. Not putting any foam on the ceiling saves $3k.

The end result is R44 either way. The advantage of the foam is that its a really, really tight seal. But I'm thinking while that's great its probably not worth another $3k.

 

[blueriver]

Okay why not also insulate the sidewalls and use vapor barrier on them and no foam ... thus saving another $8K ??

 

[LD1]

Okay why not also insulate the sidewalls and use vapor barrier on them and no foam ... thus saving another $8K ??

Agreed. If you are going to the expense of foaming the walls, why not do the ceiling.

One of the biggest advantages of foam is its air-tightness.

IMO, if you dont do the ceiling, no point in doing the walls. Just use fiberglass batts @ 1/2 the cost.

And I still dont understand the blown-in in the ceiling w/foam. Why not just spray enough foam and be done?? From what I understand, labor is most of the cost of the foam. And if they are already up their, I dont see it costing much more to just spray a little more vs only spraying a little, and then setting up the blower and blowing in.

 

[MNBobcat]

The material cost of the foam is what is expensive. They spray enough on the ceiling to make a vapor barrier and then install the less expensive cellulose to get the R rating.

The walls leak around every ridge in the metal. I have mice using the ridges to enter/exit the building at ground level. I'm going with the foam on the walls because it plugs all those ridges and makes a super air-tight seal. There is no doubt foam is the best insulation. Its a balance between cost/benefit. The foam will get into every cavity (between rim joists, for example) and really seal things up.