Last week, we applied a single layer of spray foam ("Is Great Stuff good?") over all the walls and doors (besides up front, which we will insulate without spray foam, or spray later).
Brooke then wrote down our next steps to insulate and finish the walls.
1. Take measurements of the walls/windows, The van, like many vehicles, has a lot of many irregular shapes and sizes, curves and measurements that taper, so getting it right is harder than it seems.
2. Put Reflectix loosely over all the spray foamed walls, generating a dead airspace on either side of most of the Reflectix, which is what it needs to insulate well.
On dead air spaces & too much fiberglass insulationWe may or may not put some pink insulation in that airspace, but I tend to think that the empty airspace will work better with the Reflectix because of its radiant insulation properties, while pink insulation may actually do more harm than good, by having heat pass through it and the Reflectix to the walls. A friend with decades of engineering experience advised that dead air was the best insulator in a conversion van, so we are trying to keep that in mind as we test what works best. If in doubt, we will either return the pink insulation or use it elsewhere, but keep in mind that it's the dead air that makes insulation effective too, so stuffing as much as you can into a tight space will only lower your R values.)
3. Use the Reflectix as a template for the panels. The panels must be larger than the Reflectix cuts because they will be coming out more (more 3d formed) and must closely follow bends. We are using thin, white PVC-faced boards cut 2'x4' for convenience. We could have used larger pieces to keep sections more whole, but we're going to have a lot of work making the joints look good between walls/floors/windows etc anyway, so we're not worried about it. We are much more worried about the walls actually sealing in the air/dust/fiberglass than looking good. Some or a lot of the walls may be covered with material or tapestry to help hold heat anyway, like they did in ancient castles.
4. Glue the Reflectix to the spray foamed walls. We want it only as tight to the wall as it has to be to insure it isn't making noise. The unevenness of the spray foam wall should be perfect, because the Reflectix will adhere the high points while everywhere else will have a gap of dead airspace, which is how Reflectix achieves high insulation values (insulation against radiant energy, not conductive energy so much.) Reflectix without a dead airspace around it only has an R-value of 1 because the only radiation insulation happening is in the thin bubblewrap layer sandwiched between the reflective layers.
5. Put in braces for the walls. Forgot the proper construction term, but we screw 1x4's into the walls through the Reflectix and spray foam so that we can screw the walls into those and give them a little more shape and strength.
6. Screw in the walls.
7. Make joints, prime, sand, finish.