This post is a contribution I made to a reddit.com discussion. Since I spend a fair amount of time discussing the various aspects of van-building on reddit.com, I’ve decided to copy those discussions here for posterity. Please note, however, through these discussions I tend to learn new ideas and change my own perspectives. The snippets I’ve memorialized here are merely a snapshot in time.
I keep seeing these rants and PSAs about Reflectix come across where people say it should never ever be used in camper builds. While that may be true if your only hope is to get the advertised R6 or whatever, I think the stuff serves some other very important purposes.
The way I apply it is to glue it thoroughly to the inside of the sheet metal. While it may not give you true R6 when glued to the surface, it does make a tremendous difference. Halfway through my current build, I had one section of the wall covered and another section uncovered, and in full morning sun the uncovered section would bake and the covered section would be nice and cool. That’s a very simple test, but it shows that Reflectix does something.
Another use: sound deadening. It’s a heck of a lot cheaper than the real sound dampening material and a lot lighter, too. It may not work as well, but it does make a difference. Same application, glued to the sheet metal.
Another use: Widen the thermal gradient as the sheet metal surface to deter the formation of condensation.
A lot of time and hubbub goes into people trying to figure out the proper bulk insulative material. Fiberglass supposedly breaks down and gives you cancer, though I’ve not read any empirical analysis of this. Spray foam is costly and if applied improperly can offgas. Recycled denim is cheap, but absorbs water so condensation becomes a touchy subject. Wool is a bit costly, and honestly I don’t know much else about it. I know wool clothing also absorbs water and takes forever to dry. Polyiso board sealed in with squirt foam is about as good as a full application of spray foam, but is difficult if you have lots of odd surfaces. You must also ensure you entirely seal your pieces to the sheet metal to ensure no moisture becomes trapped behind the panels. Thinsulate seems to be a pretty good option, but dang costly. And it bugs me that Hein drops in in almost every forum on insulation trying to sell you his product.
What I’ve found to be my preferred method is, instead of worrying so so much about preventing condensation, worry about how to handle it when it does happen. Thus I apply reflectix to all the sheet metal surfaces to, as I said before, widen the thermal gradient (condensation forms when hot meets cold within a narrow gradient). Then I use recycled denim on top of that. I’m currently on a winter trip where I’ve been using my current build in sub-zero temps while cooking inside in the evening. I have some unfinished spots on the walls where I can reach in, dig through the insulation and feel for any moisture and so far, I’ve found none.
Once I get back home and make some finishing touches, my plan is to install a handful of 120mm computer fans in the walls so that if I have any real fears of condensation, I will just turn the fans on during the day to circulate dry air through the walls.
So with $40 in reflectix and $40 in denim, I’ve got all my walls fully insulated and am very happy with the results.