Insulation for vehicles – if not Reflectix, then what?
Much thanks to everyone here for the great comments on Reflectix on the other Q&As. I’m glad I read them before I bought any!
But now I am stumped. This is one of the main recommendations on the RV-builder forums for insulating a vehicle to avoid condensation and keep warm/cool.
I am preparing a Chevy Express cargo van for research work (using it as office/sleeping area). It has a steel skin, and hollow steel “studs” spaced about 2 feet apart, about 3″ deep between. Ceiling is similar. Also, there are voids in those “studs” and in the door recesses. (http://bit.ly/HRnArM for a pic).
It’ll be used in northern Canada in the summer and southern BC in the fall, so 60 – 90 deg. F days, and 25 – 80 deg. F nights (w/ a few 90 deg. nights maybe). I won’t be in it in the day much, so that isn’t so crucial (though I’ll only have a cooler, vs fridge, so it’s a concern), but at night I want to be sure to avoid condensation and either keep the heat in when it’s cold out (75% of the time) or keep the hot out when it’s hot (rarely). I’ll have a vent fan so that should help with pulling in cool air on hot nights.
I was considering applying Reflectix to the skin and then another layer over the studs throughout as a vapor barrier. But apparently that may not be very effective. I’m not sure what to put in the voids, though, as fiberglass isn’t so good when moist, similar with jute, cotton, etc. etc. And similarly, whether I should just use plain foil as a vapor barrier, or if Reflectix might have some application there.
Any suggestions for materials and application? Or other resources I could use to get a handle on this? Much thanks in advance.
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Replies
What do the refrigeration trailers do? Are those spray foamed and covered? I would think you'd want something somewhat vapor open on the inside, as the walls sure won't be drying a lot to the outside.
Dylan,
To me, there is only one choice for this application: closed cell polyurethane spray foam, which will provide both the vapor control you need and the insulation value. The steel studs are a problem because they conduct the heat/cold and it would be good if you could find a way to spray foam over them also and not just in between them.
A couple of years ago we foamed the box of a large truck that is now a mobile operating theater in Tanzania. We only had room for about 2 inches of foam but by all accounts, it is working extremely well.
Dylan,
Just saw John's post and I disagree. Go with the closed cell material. You must prevent the interior moisture from reaching the metal skin but there is no need to be concerned about any flow from the outside in.
SPF (a Dow froth pack should do the trick) to keep heat in, and ventilation for condensation control. Doesn't matter what kind or how much insulation you put in it, if sunlight is hitting the windows, it'll heat up. Get a portable picnic shelter for shade.
SPF (a Dow froth pack should do the trick) to keep heat in, and ventilation for condensation control. Doesn't matter what kind or how much insulation you put in it, if sunlight is hitting the windows, it'll heat up. Get a portable picnic shelter for shade.
Thorsten: OK, you surely have more experience than me. My concern was this, though: On a moving box that big, surely there would be "racking and rolling", to play on words, and the foam would be getting cracks in it, letting air out to the outside and then needing to dry inward. Apparently the Tanzanian truck is proving my worries unjustified, though.
Closed cell spray foam does seem to be quite popular in this application (although perhaps more for contractor than RV use). I had concerns about moisture getting into/behind the foam but wasn't aware that it can act as a vapour barrier.
Unless anyone has other ideas, I will get some quotes on that option. I was hoping for a cheaper/DIY option but quality is #1.
What most people won’t tell you is that if the spray foam insulation isn’t done properly, then when there is an abrupt change in the heating climate, for instance in summer, any uncured insulation will cause the remaining foam to expand and turn your vans walls into an oil canned disaster. Google something to the effect of spray foam van disaster and you’ll get an idea. If you spray foam, go in small thin layers to give all of the components a chance to react. Otherwise, go with 3M Thinsulate , Which has been supplying insulation for vehicle manufacturers for years. That’s what all of the high dollar upscale bam companies use. It does sound and thermal insulation at the same time. Or, do what I did, and put in poly iso-in the cavities, cut into as close of chunks as you can, and then use a single part foam come out like great stuff, with the applicator gone to fill in the nooks and crannies between the panels. I used 1 inch poly iso-, and then went over the top of that with Since late. White paint on the roof adds to the heat reflection, and in the desert at Burning Man I’m fairly comfortable without air-conditioning. Any condensation from my breathing and the atmosphere is captured by the insulate, and then re-absorbed when the heater is on or air conditioning while driving, so no vapor makes it this way to the van’s skin. I’ve use my van and negative temperatures in Colorado at altitude and out to Burning Man in August son, and I’m very satisfied.
Cheers,
Greg