Closed cell over vinyl backed?

[USAFpj]

A lot of spray foam threads, but even with the search function, I didn't see any answers on this:

I have your 'run of the mill' 3in vinyl backed insulation on the walls and roof of my pole barn. The company stated that they advertise it as R6, but was upfront that they use it more as a condensation control vs. R valued product. So my question is can closed cell spray foam be applied over this vinyl backed insulation?

Seems to me that it should be sprayed directly to the metal, but I believe that Green Building Advisor stated that it would be fine to do so?

I live in a mild climate, and feel that if I spray foamed this 30x50x14, I may never need to heat or cool it. Thanks for your insight!

http://www.garagejournal.com/forum/attachment.php?attachmentid=540345&stc=1&d=1459163697

 

[CharlestonJoe]

Seems like the vinyl back would have to go. What is your plans for the inside of the pole barn? The spray foam installers would blast a layer over everything and then what?
For long term I can't see that foam sticking to the vinyl forever. I know initially it would.
I'm really curious as to what others will have to say.

 

[USAFpj]

Joe, the initial plans is to house/maintain some WWII vehicles, and a second floor for antiques storage. As I've not worked in a shop this large, and since returning back home to the humid South, I can't say if I'm going to need more heat or cooling than what the building will give me, know what I mean?

But before I start moving everything in, now is the time to get the answer!

 

[DC73]

Agree with GBA. The closed cell foam is a vapor barrier in and of itself. The vinyl backing on the existing insulation would be of little consequence since you are not creating a situation where moisture could be trapped between two barriers. Be careful putting any other form of insulation in direct contact with that vinyl backing or you could create a moisture sandwich. Best to check your details with GBA on the Q&A forum.

DC

 

[Voi]

So my question is can closed cell spray foam be applied over this vinyl backed insulation?

It looks to me like those girts are over the top of the vinyl backing? Are they structural girts or just additional girts added to keep the insulation in place? Did you actually ask the question over there or did you find a similar discussion in the Q&A section?

My guess is the people at GBA will not like the closed cell foam idea if those girts can't come down since they would be trapped in the middle of a vapor barrier envelope (no direction for the wood to dry towards).

They tend to direct people towards open cell in situations where there is any question about wood possibly being trapped between vapor retarders.

 

[USAFpj]

Voi, good observation. I did not ask the question, just found one similar. The answer for that question may not be right for mine. Got it.

 

[raymondtm]

Hi, all. Just checking in to see how this project went. I am at a decision point on adding insulation to a metal building. I have the standard 3" vinyl insulation, and have the inside of the building studded out. Should I just put standard FG bats between the studs? There would be a couple inches of space between the FG and the existing vinyl. Or, spray foam onto the vinyl? Or, just don't add more insulation. See attached photo of current state of progress, except that since the photo was taken I have done the wiring and lighting. Next step is awaiting decision on insulation. Thought are welcomed!

 

[raymondtm]

THanks, everyone. I have been told by a couple insulation businesses, and one foam insulation company, that I shouldn't blow the foam onto the vinyl backing. Any thoughts? And, 2, if that's the case, i'm back to installing fiber glass batts. That's ok, and will leave a few inches of air space between it and the vinyl. Is that problem, and should I put a couple vents in the top of the building eaves (like a traditional attic vents) to vent that space? I'm concerned a bit about the red iron sweating inside that air gap.

 

[Mennoknight]

THanks, everyone. I have been told by a couple insulation businesses, and one foam insulation company, that I shouldn't blow the foam onto the vinyl backing. Any thoughts? And, 2, if that's the case, i'm back to installing fiber glass batts. That's ok, and will leave a few inches of air space between it and the vinyl. Is that problem, and should I put a couple vents in the top of the building eaves (like a traditional attic vents) to vent that space? I'm concerned a bit about the red iron sweating inside that air gap.

I am in the same situation right now and was wondering what you ended up doing?

 

[drewyoung7]

THanks, everyone. I have been told by a couple insulation businesses, and one foam insulation company, that I shouldn't blow the foam onto the vinyl backing. Any thoughts? And, 2, if that's the case, i'm back to installing fiber glass batts. That's ok, and will leave a few inches of air space between it and the vinyl. Is that problem, and should I put a couple vents in the top of the building eaves (like a traditional attic vents) to vent that space? I'm concerned a bit about the red iron sweating inside that air gap.

What did you end up doing?

 

[BurtEggley]

The humidity will get in there during the day and approach 100% at night may nights in summer unless the air is dehumidified with an AC unit. If you have ever lived in the south, you know that even a closed up home, fully insulated but with the AC out reaches 80F -90F at night inside and is almost unbearable as the pillows and bed approach soaking wet - as your body tries to cool. As a child, that is why windows were open at night, to let a breeze thru. The point being that even inside a fully sealed house with high R value insulation, it still gets way humid and hot at night. Your WWII collection may rust in that humidity regardless of the R value unless you add conditioning.