What type of insulation should I use?

[thomastedder]

I've done some looking around and have narrowed it down to either 1" styrofoam insulation (R5) or 1/4" radiant barrier insulation (R14.5 supposedly). The link to the radiant stuff is Here http://www.insulation4less.com/highr_FfmF.asp.
Has anyone used this stuff? If so, can it really do what the website says? I think the bus already has about an inch of regular fiberglass insulation in the walls. Also, how much of a difference would the 1" foam make, since it's only R5?

[Eric von Kleist]

Be careful in evaluating the R value claims of the foil/bubble stuff. There are different qualities that are evaluated in different ways. From what I remember reading about the bubble/foil stuff, you need to have a 1/2" air gap between the insulation and the surface against which you are insulating. The radiant barrier insulation works well against radiated heat, but not as well against conducted heat, where its R-value is far less than the 14 or that is printed in big letters on the packaging.

If you are insulating a floor conducted heat gain/loss, I think that the cheaper way to go would be the 3/4" foamboard. I would use the 3/4" instead of the 1" because the 1"x2" material commonly used for furring strips is 3/4" thick: if you use the 1" foamboard, you'll have to cut special furring strips to a 1" thickness.

In the ceiling you might use a combination of the two. I just left the old fiberglass insulation in my ceiling, and it seems to be working well enough. Of course, I can't recommend strongly enough that you paint your roof a gloss white. It really rejects heat very well. The only issues that I have with heat transmission through my ceiling are where the beams make metal to metal contact between the inner and outer skin. I am going to remedy that this spring (hopefully) by installing a 1/4" layer of foam (R-1) over the entire ceiling, and then putting some kind of decorative covering over that. That will break the direct connection between the roof and the interior of the bus, and should keep the bus warmer/cooler.

[DigDug]

I used two layers of .75 RMAX rigid insulation. Works very well, much better than my stock insulation. It has a shiny side for radiant barrier on one side. I kerfed it and it molds to radius very well. It has a R-value of 5 per .75 inch.

I also experiemented with Reflectix, which is a bubble foil. Didn't work very with no gap, due to Conduction. As Eric pointed out, .5 inch gap of air really helped the bubble foil, but I didn't want to lose the space with furring strips.

I did three tests. I taped reflectix to back of .75 inch RMAX in one 3x4 foot spot. I put one .75 inch RMAX in second spot, and two layers in the third spot.

The reflectix was within 1 degree (cooler) of the third spot. I tried to test in the morning, so ambient temperature would not have an affect, but I'm sure there was some degree of inaccuracyt!!!!

I decided to go with two layers, as 1) I didn't feel the time involved justified the savings 2) Two layers of insulation would be superior for winter

There are many ways to skin a cat; hope this helps.

Best of luck!!!

Dug
75 MC8
Arcadia, FL

[bdavis441]

speaking of painting the roof white.......
There is a thermal insulating coating available from McMaster-Carr that we use at work sometimes. I was reading the labels and this stuff is UNBELIEVABLE. Two coats rolled on for a 20 mil thickness (it's thick) will insulate to an R20 and block 90% of radiant heat. They also say that two coats is equal to 4 to 6 inches of polyurethane foam. It's about $40 per gallon, one gallon only covers 100 sq. ft. at two coats. So that's about 3 gallons for a roof. $120 dollars is a bargain with these results! I'm gonna try it.

[busone]

Let us all know how that works out Brad. It sounds too good to be true. I do hope it works. It could save us all some money/time on insulation.

I am going to use expanding foam. I will temporarly bolt a sheet of plywood to the inside of the bus then pour the foam in. I am going to of course do a test first. In theory the stuff should expand up and not bow the exterior wall out. This should be just as good as spray foam but lots cheaper if it works. I will post the results when I do it.

They use this stuff for making figures for theater stuff. I would think if it expands poorly it would ruin the molds they use. If this works good enough I will insulate my house the same way. When I replace the lathe and plaster I will use the sheet of plywood to hold the foam in while it expands then after it is done install the drywall.

here it is
http://www.marinefoam.com/polyurethanefoam.html

[bdavis441]

I'll know how well this stuff works when I drive to Florida in June. I did some more reading on it. It is made of "glass microspheres" in an acrylic base. In layman terms, I believe that would be "little air-filled glass balls in some thick white stuff". The theory makes sense. If it really works as the manufacturer claims, I would think every sane skoolie owner (if there is such a thing) would coat their roofs with it. I'll let everyone know how it works, If someone beats me to it, let me know!

The pour in foam sounds like a good idea, I have made racecar seat forms with it. (driver sits on a big trash bag, pour the foam in, it expands around the drivers form, you then have an exact fitting form to trim and shape. We used dock foam (for boat docks) I think it will work for you.

[lapeer20m]

IF i was gonna build a bus to live in, I think i would put 2 or 3 inches of spray foam insulation on floor walls and ceiling.


but tha'ts pretty extreme.

there has also been discussion of the spray foam insulation eating metal.....but i'm sure the spray foam guy has good data on that subject. I know 2 people who had their steel pole buildings sprayed inside.

[thomastedder]

Well I just went with 1" styrofoam. I got enough to do the walls for a little over a hundred dollars. I'll glue them to the walls, then screw the wood paneling over that.

[DigDug]

Forgot to mention, RMAX is pretty flammable. I threw some scraps in a fire, and it really took off.

HTH...