Air gap and wall insulation?

[jennynic]

So, I have been reading here and googling looking for info on where to leave an air gap in the insulation process. I have my sheet metal interior walls out from under the windows and ready for insulation. I have rigid foam for this. Does the air gap go between the outside metal wall and the foam or between the inside wall, which will be wood, and the foam. I have read opinions on both ways but was seeking opinions from seasoned skoolies on which way is best on a bus?

Many thanks :greetings:

 

[TAOLIK]

Heya,

Anyone can say that "this is the best way" but without proof it's just some words. The general philosophy around here seems to be "try it out and report back with details". What I reccommend to you though is to use reflectix or some sort of radiant barrier around your airgap which will be between 1/8" to 3/4". Whether you put it outside your foam or inside is up to you, but I would do outside first, then maybe inside again if you're feeling it. The concept behind it seems to be something along the lines of the air gap acts with the radiant barrier to trap the temperature and protect it from outside. Or something like that, but I have no credibility to confirm this nor do I have a finished bus with any tested results.

Also, protip if you haven't already. Search Via googling "site:skoolie.net YOUR SEARCH INQUIRY" Also use google images it's a nice alternate way of looking.

 

[retiredChemist]

Ideally an air gap both sides. But gap between metal and the foam will give less heat transfer to the insulation and improve the inside temp for the same insulation.

 

[PigPen-SKO]

Do most people actually put in the air gap? If so, what size?

Also, how? Do you put 1/8" spacers on the wall and then glue the insulation to that?

I know that spray foam is the better choice and would negate the need to consider this, but we're probably going to use polyiso boards...

 

[jennynic]

insulation air gap

After posting this original question, I ultimately decided to use the air gap in the walls. The 1/8 gap is a minimum gap, so I guessed that a bigger air gap would be okay and used small pieces of the scrap poly insulation as furring strips that would go between the insulation sheet and the exterior wall. I glued them with the tiniest amount of glue to the sheet of insulation in all four corners and the center before I set the insulation sheet in the wall panel. I then put my pine panel T&G over that. It works so far. The main heat source from the sun seems to be the windows and the metal frames that surround the windows. The wall feels cool to the touch. I never replaced the original insulation in the ceiling. It also stays cool to the touch in the sun so I figured why bother. I have white paint on the exterior roof to help reflect heat.

Jenny