Introduction: Spray Foam Insulation

About: I am currently converting a 1988 40' Bluebird school bus into a motor-home / workshop that I plan to live, work and travel in. This is my second such project. This one will probably be my retirement home. Sti…

How do you keep warm living in a school bus? School buses were made for short distance transportation. Not for long term living. Even during that short distance transport the occupants are usually dressed for the season with winter wear if the need be. So even though there is some insulation in a school bus it is no where nearly sufficient for long term habitation. So what do you do?

Well, you could hunker down and bundle up. Or do the best you can to insulate and heat your living area. So, here we are again. The wheels once again start churning. The options are endless. Fiberglass insulation. Solid foam. Reflectix insulation. Cotton Batts (aka “Blue Jeans”). And on and on. I knew from the beginning that I wanted to go with closed cell spray foam insulation. I looked into contracting the job out. I got professional bids from $1,600 - $2,000 plus. I was leaning in that direction as I never did this before and was very leary of the hazmat issues.

As life would have it I was not allowed that luxury. Time and money never came together at the same time so I ended up having to DIY (do it myself) and like it.

Step 1: Supply List

The supply list is very simple.

  • Foam spray. (I bought mine from "Foam it Green")
  • Respirator with a Organic Vapor/Acid Gas/P100 rating. (Homedepot)
  • Your project subject (my bus)
  • And a lot of nerve (had to rent some)
  • A serrated edge knife for trimming (I ended up using a multi function tool with a half moon blade)
  • Hazmat suit (included with kit)

While researching this I realized the need to use closed cell foam vs. open cell foam. Closed cell foam is waterproof. This is important for preventing mold and mildew. One way to tell the difference is that closed cell foam has to be mixed during installation. If it comes as a single component, shake and ready to spray can, it is most likely open cell.

Generally speaking, closed cell foams consist of trapped gas bubbles formed during the foam’s expansion and cure. These gas bubbles consist of the blowing agent, and are permanently locked into place during the curing of the foam. The trapped gas increases the insulation capability of the cured foam. The cured foam must be strong and of a medium density in order to lock in the gas bubbles. The foam’s strength, coupled with its closed cell nature, enable it to resist liquid water and function as a vapor retarder.
Open-Cell foams, however, are quite different in nature. The blowing agent gas is not trapped by the forming cells, and instead is released to the atmosphere during foam expansion and curing. The foam cells have “holes” in their walls, enabling them to interlock and interconnect. The spaces within the cells are filled with atmospheric air, much like a sponge. Due to its porous nature, open cell foam does not resist liquid water or water vapor (humidity). Without trapped gas bubbles, open cell foams also do not need to be as strong and therefore are less dense than closed cell foams. (

Step 2: Read, Watch Videos (and Then Watch Them Again)

Once I ordered the kit I read everything I could on their website on what to do and what not to do. I watched all the videos on their website. I have to admit, I was very leary about the whole process which is why I wanted to contract it out in the beginning. Just the fact that you have to wear a mask that protects you against breathing acid... Makes you want to think. I called them to question anything I didn't understand. They were very helpful and responsive.


Step 3: Spray Away!

Actually the process was no where near as bad as I'd thought it would be. If you read and follow the instructions it flows fairly simple. Watch the videos on their website and it goes just as shown.

I've included a few videos of my own process for your amusement. You can title it, "The Michelin Man In The Hazmat Suit"

Step 4: Why I'm Posting This Now!

I have not finished insulating the entire bus. I ran out of foam with about another 50 square feet to go. I was going to wait until I finished the entire project before I posted this instructable. I'm currently workamping in Kansas. You know, where Dorothy and Toto got blown around! Well, the temperature last night got down to 23 degrees. I didn't realize it until the morning when my outside water was froze. As far as I can tell the inside temperature never got below 60 degrees. I have two electric space heaters going. Some of you may recall that this is my second bus project. My first bus I used rigid foam board and taped the seams with insulating tape. It was always cold and drafty. I was extremely surprised this morning when I realized how cold it had gotten last night. Once I got my water un-froze I was compelled to sit down and write this instructable. I had always planned to finish insulating the bus once the weather is agreeable again (you can only spray under ideal temperatures). Now I definitely WILL finish insulating first chance I get.

Step 5: Statistics

My bus is forty feet long by seven feet six inches wide. About six feet floor to ceiling. I'd figured I'd need about 1,000 square feet of foam. The kit I bought was rated for 600 square feet at 1 inch thick. I'm sure I didn't get everything one inch thick evenly. I know some spots are much thicker. Some may be thinner. I had only expected to be able to spray just over half the bus with one kit. I will finish up with their 200 square foot kit and have enough to touch up other areas. I built boxes around all four wheel wells and filled them with the spray foam also. Great for insulating and sound deadening on the road.

The next phase of this project is to finish my in-floor heating system which when combined with the spray foam insulation should make the bus very toasty. I've already installed about 300 feet of PEX Radiant tubing in the floor of the bus and am in the process of connecting the circulating pumps and regulators. Gotta hurry before the cold really sets in.

I paid approximately $700 with shipping for the first kit. Even with the second kit at about $400 (depending on where I have it shipped to) I'd save about $900 over the highest estimate I'd gotten. I also received a $50 coupon to use for the second kit.

The entire process took two days. That's because I didn't think I'd get as far as I did with the kit. I'd only prepared half the bus for spraying. If I had been better prepared I believe I could have sprayed the entire bus in about two - three hours. It is ready to move in condition within fifteen minutes after your last spraying. No lingering fumes or odors.

I also ordered an infrared thermometer which should arrive next week. I will update this with accurate statistics then.

As usual there is much more to come. You can follow my entire school bus conversion and my travels at

Thanks for looking,