How to Insulate a Skoolie Conversion | What Type of Insulation Should I Use?
One of the questions we get asked the most is how are we going to keep the bus warm?
The answer is fairly simple: good insulation and a mini wood-burning stove.
While that answer is simple, figuring out what insulation option was best for us wasn't so easy. It took some research and asking around before we found a product we liked.
I'd like to share some of what I learned along the way and describe our experience using spray foam to insulate our skoolie.
Here are some shortcuts:
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Before I even mention adding insulation, I need to address the nasty insulation that most likely came in your bus. Our walls and ceiling were filled with a fiberglass insulation mat that was just disgusting and really didn't do much to keep the bus warm anyways. We removed this insulation when we gutted our bus. It left behind chunks and loose fibers stuck to the walls so we wiped the excess off with a rag and vacuumed the rest.
When you take this out, it would be best if you wear a mask and gloves. The little bits of glass can irritate your skin and lungs. I didn't even think about this when I first started removing it and I wiped my face with the back of my hand. For a month or two afterwards, I had little bumps around my eyes and nose like a rash where I irritated my skin with the fiberglass. Don't be like me!
There are lots of ways that you could go and all the different brands are going to claim to have the best version. Some work better than others, some are really expensive, and some are easier to use.
There are a few types of insulation that are more common than others. And some just won't work in a skoolie conversion. You want something that prevents condensation on your walls, is fairly thin while keeping its ability to insulate well. Also, if weight is a concern for your build, that's something that may help determine which option works best for you.
When it comes to rating the effectiveness of insulation, it is measured by "r-value". R-value is the way insulation is measured for its resistance to heat flow per inch. The higher the r-value, the better insulation it is. You'll hear me use this term throughout this post.
This is a great option for those who want to use all-natural materials. It's also great at insulating! Wool insulation has an r-value rating of 3.5-3.8 (.3 to .6 points higher than fiberglass and cellulose options), manages moisture really well, and can last a lifetime. It is easy to work with, isn't full of chemicals, and is noncombustible.
You can find wool in mats/rolls and as loose stuffing. Different companies will have different methods of binding the wool together, and if using all-natural materials is your thing, make sure to see what they use to hold the fibers together.
One thing that I like about this option is that it won't be noisy in your walls while your conversion is on the move. Spray foam and rigid board sometimes squeak as the walls shift and run on the insulation while on the road. This is something wool won't do.
There are a couple of downsides to this option though. First of all, wool is expensive! Just think of how many shaved sheep it would have taken to insulate our 40-foot school bus. That's why it is so expensive.
Another downside to wool is that it isn't applied directly to the wall's surface. Since all our exterior walls are metal, condensation is a huge problem and having a gap between the wall and insulation makes condensation possible. If you can really squeeze your wool in there and cover all your surfaces, the moisture managing properties of wool should do you just fine.
Foam Board / Rigid Foam
Think of those giant sheets of stiff foam you see at Lowe's or Home Depot.
These foam boards are relatively thin and super light, yet they still maintain a high thermal resistance. The r-value for rigid foam ranges depending on the brand and thickness of the board you buy. We used a small amount of this insulation when we ran out of spray foam and it was about an inch and a half thick. This thickness usually has around 6 to 10 points from what I've found. This is a higher rating than most options including spray foam.
The downside to this option is all the cutting you're going to have to do in order to make it fit where you need it to. Additionally, it is easy to be left with an air gap between the wall and insulation which can lead to condensation. So while it has a high r-value, this won't save the gaps that didn't get covered.
Let me start by saying there are really two types of spray foam insulation and it has to do with the density of the cells. Closed-cell spray foam is dense and the cells are filled with gas which pushes the foam into all the little gaps possible. Open-cell spray foam is not as dense and isn't filled with gas which means there are air bubbles and leaves the foam spongey. Closed-cell is the way to go for insulating a conversion.
Closed-cell spray foam has an excellent r-value (6 points per square inch) and protects your walls from condensation really well since the foam won't absorb water or let any moisture through. And since it is applied directly to the wall, there is no gap between the wall and insulation for condensation to occur.
This is a really good option for van and bus conversions because it is easy to get into those weird shapes and awkward angles.
We all know there is nothing straight in a school bus!
There are some downsides to spray foam insulation though. First off, it is all chemical based, which can be an issue for some people and requires a respirator to apply the foam. Another thing to take into consideration is the price of this option. To cover roughly 600 square feet, we spent about $1,600 on spray foam. And lastly, this option has a bit of a learning curve to install. Getting a nice uniform layer and the right thickness is difficult at first. On top of that, once you start spraying, you can't stop until you have run out of spray foam. This makes for a tiring 45 minutes or so per spray foam kit.
To fill in any small gaps or awkward spots that didn't get covered, this spay foam pack is great! We originally bought a few cans of this from Lowe's, but this is a much better setup and will make for less trips to the store.
This is going to be the cheapest option but also the worst. This is the stuff we pulled out of our skoolie. It has a low r-value and is gross (and sometimes dangerous) to work with. I wouldn't recommend it, and most others would agree with me on that.
What We Chose
Matthew and I decided to go with spray foam insulation since it seemed like the wisest way to go.
For starters, spray foam has a really good r-value. The spray foam that we went with has an r-value of 6 per inch, and we did our layer probably two to there inches thick.
Condensation is a huge issue for skoolies. If you let the condensation into your walls, it will start to rot your walls and cause mold issues.
So that's another reason we went with spray foam. Spray foam doesn't leave any air gaps on the wall where water could condensate because it is sprayed directly onto the wall. If you stuff wool or solid core insulation into the walls, it most likely won't be completely touching and covering the wall making condensation an issue.
We found Tiger Foam online and really liked it, so we bought directly from them. Of course, you can get a spray foam kit from a hardware store online just fine.
Since the tanks are under pressure, they can't be flown for delivery. It did take a while to get our order for that reason.
It comes as two tanks of different parts of the solution that get mixed with a nozzle when you spray it. Each kit that we got covers approximately 300 square feet. We needed two of these kits to cover our 40-foot school bus.
It was expensive but well worth it. Each kit cost about $800 and we needed two... So it's a good chunk of change.
Matthew was the "lucky" one who got to apply the spray foam. It required wearing a full body paint suit, booties, goggles, and a respirator. This is some nasty stuff and makes a mess!
Once you start spraying it, you can't stop. If the solution sets in the nozzle and hoses, you won't be able to get going again. Fortunately, the kit came with a few extra nozzles so we could switch it out when needed.
I'll admit, we could have done a better job with the drop cloth and taped off a few more things. It was a breezy day and we had no idea how messy this stuff was, so we ended up with some overspray on things we would rather not have it on. Our front windshield and side mirror have a few specks on them, clumps landed on the floor, and our space heater got covered. Lucky for us, most of it scraped off just fine.
We sprayed the insulation on the walls, ceiling, and as many other surfaces as we could. It is important not to leave gaps of the metal walls exposed since water will condensate there. The foam won't absorb water or let water pass through it, but it can't protect areas that aren't covered. So, after we blew through our $1,600 worth of Tiger Foam, we bought a few small cans of spray foam and filled in any of those little gaps we found.
"This was much easier and I was able to do it without a respirator!
I will mention that the second kit we got had a hole in the hose. We did not know this until we started spraying and a large about of ooze started spewing from the tank and onto the floor. We quickly took some super-glue and a variety of tapes to it in hopes to stop the leak and save the hose. It worked for the most part, but I would recommend just getting a different kit instead.
The problem is that we lost some of the solution in that tank. The spray foam works by mixing the two parts together. Now we had the wrong ratio. For a while this didn't affect the process too much. However, once we got to the last few square feet, it didn't mix well at all. The ratio was so off that it stayed this gooey mixture that never solidified. It sort of just melted off the wall and made a sticky mess all over the floor.
A few days later, we notices some green streaks on the side of our bus. Yup. The ooze had seeped through the gap in the sheet metal and started dripping down the side of the bus. We still haven't gotten it off. We'll do some more cleaning and then hopefully it'll get covered when we paint the mural on the side of our bus.
Matthew stopped spraying once he saw that it wasn't mixing right, but we still had some bare wall space that needed insulation. We weren't about to buy another kit of spray foam, so we bought a sheet of rigid foam insulation and cut that to fit in the bare spots. If you've seen pictures of our bathroom without all the walls in, you've seen how wacky the patchwork insulation job looks in there. And now you know why it looks so bad.
In case you haven't seen it, here you go.
That last thing that I'd like to mention about our spray foam experience is about putting walls over the foam. We didn't get a perfectly even layer of foam and some of it ended up on the ribs and wall supports. We used a flush saw like this one to cut down any areas that stuck out too far or covered surfaces we needed to be clear. It cuts easily, so this process wasn't that bad.
Insulating The Floor
We opted out of insulating our floor. I've seen a lot of builds who have insulated their floors and it looks really good. Typically when I've seen this, it is done with rigid foam sheets in between the floor framing.
We decided this wasn't necessary for us. At least for now. We also didn't want to lose those inches of height in our bus. We only raised the roof 16 inches and Matthew is pretty tall, so we want to keep all the height we can.
We do plan on eventually adding insulation (most likely more spray foam) to the top of the underbody storage that would insulate the floor. That's a job for later though.
Insulating your bus is vitally important no matter which climate you are going to be in. Having the right insulation will keep you warm in the winter and cool in summer while also keeping the moisture out.
You've heard me say it before, and you'll hear me say it again. Condensation is going to be one of your biggest problems if you don't address it properly. Having insulation all the way up to the exterior wall and filling in all the little gaps is the best way to fight this. Anywhere that there is exposed metal, is an opportunity for water to get into your bus.
Wool and rigid foam are both great insulation options. However, we felt that going with spray foam was best for us. We loved that it would block all condensation and was able to get into all the awkward gaps throughout the bus.
Insulating your floor is a smart idea in most cases. We haven't insulated our floor as of now, but are planning to add insulation to the underbody storage which will help insulate the floor. With cold hardwood and tile floors, slippers will likely be on our feet most of the time.
I hope you learned a little about what your insulation options are and got a better idea of what you need for your build.
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