Metal Building Wall Insulation

[cthulu]

Been reading up on insulating metal buildings and I want to see what everyone thinks.

I live in the pacific northwest, rainy half the year 35F-85F variance.

Goal is to prevent condensation on the metal wall and insulate the building enough so that I can use an electric heat source, gas or wood burning is not an option.

I have 8x8 beams connected by 2x6 and 2x4 horizontal supports that the exterior metal sheeting is screwed into. I found a good deal on 2.5in thick EPS with foil backing and plan to glue/screw it onto the horizontal wooden cross beams with the foil side facing the exterior towards the air gap and metal exterior wall. From there I'll attach 1in fir strips to the horizontal cross beams through the foam and finally a .5in OSB from the 8x8 to the fir strips as they should be level.

I'm worried about which way the foil should face as from what I've read it acts as a vapor barrier. My diagram has it facing outside but with me heating the inside of the garage wouldn't that cause moisture to form in the EPS? Is a layer of vapor barrier (vinyl sheeting etc) needed for this?

Thanks guys, this site is always helpful.

I attached pictures of my diagram and the wall. Let me know if you have questions.

 

[mcclaar]

I'm looking for advise as well.

 

[Radix2]

I don't think it really matters much, 3.5 in foam is not going to pass any real amount of vapor through it, and is enough insulation that both sides should track their environments - I.e the inside should stay above dew point, which is the serious issue with thin uninsulated vapor barriers ( which is not what you have).

Since you do have an air gap, I would go with what you propose, you might get a little radiant effect in the summer in sunny spots.

You should tape the seams to prevent the warm damp inside air in the winter from getting to the cold airgap and metal.

 

[cthulu]

You should tape the seams to prevent the warm damp inside air in the winter from getting to the cold airgap and metal.

They make this cool foam board adhesive for glueing foam board too pl 300, have read good reviews but haven't tried it yet.

https://www.amazon.com/dp/B0043G3NYC/?tag=atomicindus08-20

Adheres the foam to pretty much anything. Was going to use this between the boards and their mating surfaces, figured that way I don't have to tape. I may tape anyways though as that is for sure going to be a weak point. (that and the garage doors)