I am currently ripping out the interior of a school bus that I am converting to an RV to live and travel in. I am familiar with green building techniques for homes in various climate zones with standard wood framing, but am unfamiliar with the techniques for a Steel-frame, sheet-metal-enclosed building envelope. Seeking Help!
The first step will be to seal all penetrations, windows and any seams or leaks with all-weather silicone caulk and sealant. Once the shell is sealed, I'm not sure how to deal with insulation, air and vapor barriers because I'm not sure if condensation will be an issue with the sheet metal exterior.
So, I am reaching out to you all for some insight/ideas for the following components. Keep in mind, I will have a small pellet stove for off-grid space heating that should keep the interior dry, and will have a small AC unit + fan that is run off of deep-cycle batteries with solar.
Best Practices Recommendations?
-Denim batt insulation or Eco spray foam: Which would you prefer? What are potential issues with moisture from the steel frame and sheet metal walls?
Air/Vapor barrier: Is this necessary in this type of enclosure? I will mostly be living in a heating-dominant climate, so the vapor barrier I'm familiar with is on the inside of the enclosure, in front of the insulation. Does this still work?
I don't want moisture to get trapped behind the insulation against the sheet metal of the bus and cause any issues there, so I am seeking advice if any one has some insight, I would be truly grateful.
RV's always use foam due to they want to keep as much space as possible inside though generally they are sheets. With that a properly installed CC spray foam gives you the most bang for your buck & helps ensure your don't have moisture issues on the metal skin (make sure you talk to manufacturer reps - especially on prep / prime) & eliminates need of vapor barrier as it & the metal skin is one
I agree with Sean that closed cell spray foam is the way to go. Closed cell gives you R6 to R7 per inch, compared to about half that for open cell and fibrous insulation. Also, open cell is vapor permeable and you need at least 3 inches get an effective air barrier (maybe even more, can't find my reference).
Thanks for the advice! I was hoping to get away from the foam option to be more eco-friendly with the build, I have just about 600 square feet of wall, floor and ceiling area needing coverage, other options are so pricey!
Roxul= $2,500 + rigid floor insulation
Spray foam= $800
Denim batts= $800 + need vapor barrier or some way of keeping condensation from building up + rigid floor insulation
Loose wool insulation= $560 +need vapor barrier or some way of keeping condensation from building up + rigid floor insulation
I hate having to use foam on this project, but it would definitely be cheap + easy.
Any suggestions on how to make the wall assembly work with loose wool using netting or denim batts?