Bubble wrap or Tyvek under Spray Foam?

[skippydoo]

Getting ready to build a 30x40x12 pole barn for a shop in NJ . I will be spray foaming the walls and ceiling . I will not be finishing the inside right away. My question is should I use Tyvek or double bubble wrap under the metal walls and roof? I'm told the bubble wrap will help radiate the summer heat back out and without it the heat will heat soak the spray foam and it will get hot inside the building. As of now I never plan on installing a ceiling liner, it will be open up to the roof line. I do want to install a liner on the walls. I will be heating and cooling on occasion. What's your thoughts?

 

[Radix2]

Without an air gap, the radiant barrier is not going to do anything, so between that and the fact that that stuff is expensive, there is no reason to use the bubble wrap.

Is the purpose here to prevent the spray foam from sticking to the metal?

 

[stm317]

Tyvek

 

[skippydoo]

Without an air gap, the radiant barrier is not going to do anything, so between that and the fact that that stuff is expensive, there is no reason to use the bubble wrap.

Is the purpose here to prevent the spray foam from sticking to the metal?

Yes, I don't want to spray foam right up against the metal.

 

[MrSurly]

Yes, I don't want to spray foam right up against the metal.

I’m wondering why, but rather than question your reason, I’ll take a shot at answering your question, first.
As stated, there would be zero gained by buying the foil bubble wrap in my estimation. “Heat soak” overwhelming the effect of the foam is just salesman’s BS. If you feel there needs to be a membrane between the foam and the metal, I can’t imagine any reason to use bubble wrap for this job; use Tyvek or similar.
Keep in mind that Tyvek is an air and (bulk) water barrier, it is not actually a vapor barrier OR a moisture barrier.
Those same four attributes are true of the spray foam. (That’s for Open-Cell, Closed-Cell is a vapor barrier). So the Tyvek isn’t serving any purpose OTHER than maintaining a bond separation from the metal. So now, the foam is being supported by the Tyvek.
Consider that although spray foam is light weight, it doesn’t weigh *nothing*.
How thick are you going to apply it? How well does the foam *stick* to Tyvek? I don’t know that answer.


Now you just have to determine whether there is merit to doing this.


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[toyotadriver]

I would cover the exterior in 1 inch foam sheets and then screw the metal on. Then, spray foam it. The exterior foam will help slow the thermal bridging losses.

 

[MrSurly]

I spray-foamed my 30/40/14 and used both Open- and Closed- Cell foams directly on the steel.
Too soon to tell about mature issues, but I have found that the claim that replacing/removing metal will be nightmarish is just bogus.


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