If we could give you any advice for your build, it would be this: Do not skip steps or take shortcuts, especially when it comes to bus and van conversion insulation. It just isn’t worth it! We’re headed into our second winter on the bus and are so happy we chose to insulate. Otherwise, I think we would’ve missed out on seeing a lot of awesome places, especially when it’s in the negatives.
Bus and van conversion insulation is necessary for preventing heat transfer. High-quality materials are effective at resisting heat transfer. To compare insulation materials, you’ll have to understand what an R-value is. The R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window, or a complete wall or ceiling, resists the conductive flow of heat. It’s the temperature difference per unit of heat flux needed to sustain one unit of heat flux between warmer and colder surfaces of a barrier under consistent conditions.
In this article, we’ll describe the steps it takes for insulting your rig, as well as some of the insulation options that we recommend using based on your needs.
Step 1: Assessing Your Bus & Van Conversion Insulation Needs
For one, let’s take into consideration what your bus and van conversion insulation needs are.
1. What is your budget?
Budgets can be strict, and we get it. While our project wound up going over budget, we tried to save as much money wherever we could without compromising the quality of our project. With that being said, a budget could affect how much and what type of insulation you choose.
2. Where do you plan on traveling?
Are you going to be in cold or warm regions? If there is a chance of extreme temperatures, then you’re going to want to insulate your conversion like crazy! Insulation helps your bus stay warm in the winter, cool in the summer, and reduces condensation year-round.
3. Are you keeping your bus windows?
Chances are, you won’t be replacing all of your school bus windows. Windows lose heat in the winter and bring in heat during the summer. You can combat this by building shades, blinds, or using Great Stuff. However, at the end of the day, it’s not going to be enough unless you have appropriate insulation.
4. What is your timeline?
We HIGHLY recommend insulating your entire bus, including the ceiling, walls, and floors. Regardless of the region you plan on visiting, insulating your entire bus will help with the resale value and overall quality of the conversion.
So, have an idea of where you want to put your insulation, yet? Good. Let’s get started on the entire process and options for your floors, ceiling, and walls.
Step 2: Demolishing Your Floors
Most school buses have a metal floor that is covered with either rubber & linoleum or rubber, linoleum, & wood. Don’t worry, getting your flooring demolished is not the headache that most people make it out to seem. The metal floors are durable, so simply cut into the rubber with a circular saw and use a crowbar to pull it up. Be sure to wear a mask and some goggles – the metal floor usually has rust and the wood could be rotting!
Once you have the metal exposed, use an Angle Grinder or similar tool to get rid of any exposed rust. Then, you’re going to cover all of those tiny screw holes in the floor. It may seem tedious, but we’d recommend using pennies with epoxy so that it creates an airtight seal. Others also weld the holes shut, but we chose to save time and use pennies, instead. After you seal the pennies, use a primer to prevent future rust on the metal bus floors.
Step 3: Do I Need a Thermal Break? Do I Need Frame Before Insulation?
Before choosing which insulation you want, you’ll need to screw in a thin piece of wood on the metal supports of your bus ceiling and on the walls. For our bus, we used a thermal break (a thin piece of insulation foam) between our ceiling/wall and pieces of wood. This additional add-on helps prevent vibrations, moisture, and heat transfer. We used liquid nails to secure the thin layer of insulation to the bus supports.
Note: According to Havelock Wool, you do not need a thermal break for that type of insulation. Due to the crimped nature of wool fibers, they form millions of tiny air pockets that trap air, helping to provide a thermal barrier.
Framing is not required for insulating the floor. Of course, it’s a preference and some people choose to do the extra step. However, we thought of it as unnecessary. Even with rigid foam insulation at 15psi, you’re going to have 2,000 lbs per sq. ft. of support underneath your flooring.
Step 4: Bus & Van Conversion Insulation Process for the Floors
Most people converting skoolies use at least 1in. of rigid foam for their floors. Ours is 1.5in. XPS foam. If you’re looking for some other options for rigid foam, check out the following:
Expanded Polystyrene (EPS) Foam: This foam is white and the cheapest option due to its fragility and low R-value at R-4 per inch.
Extruded Polystyrene (XPS) Foam: We used this insulation for our floors. It comes in a variety of colors, including blue, green, and pink. It reduces moisture unlike the EPS and is rated at R-5 per inch.
Polyisocyanurate (ISO) Foam: This is about 5x the cost of EPS foam and rated at R-8 per inch, but reduces to about R-6.5 per inch over time. It comes as foil-faced or paper-faced, which gives you more of a choice between moisture or non-moisture barriers. While ISO appears to have the highest R-value, studies have shown that it does not retain as high of an ISO in colder weather.
Once you chose which rigid foam works best for your needs or budget, you’re going to use an adhesive to glue it on the floor and something heavy to hold it in place while it sets. We’d recommend not using screws to avoid more holes on the metal part of the bus. Use aluminum tape to seal the seams between the foam to add even more protection.
Quick note: We installed radiant heating Pex tubing into our XPS foam flooring for our radiant system. We cut channels into the foam before putting the plywood on top. Stay tuned for a more in-depth tutorial on what we did to install our radiant heating set-up!
Other options for insulating your floor include a tar-based sound deadening product (Noico RED). Noico is a versatile insulation material with excellent thermal barrier properties. If you’re looking to save headspace in your vehicle, this could be a great, cost-effective solution for your floors.
And…onto the Plywood!
The plywood is installed similarly to the insulation: Just use adhesive and place heavy objects (we use cinder blocks) on top until it sets. We used a 5/8ths plywood.
Quick Tip: We used over 5 containers of liquid nails, so we’d definitely recommend buying in bulk to save some money. We used liquid nails on nearly everything that needed to be glued down. It’s a great adhesive that also prevents vibrations and noise during travel.
Step 5: Insulation for the Walls and Ceiling
Most people choose either spray foam, rigid foam, wool, or fiberglass for their walls and ceiling.
You still have some work to do before you insulate your walls and ceiling. Do all of your wirings throughout the bus before installing the insulation. And, as a bonus pro tip: Make sure you put your wires in an easily accessible spot if you’re doing spray foam. We were forced to dig our wires out before installing our ceiling!
Even though we convert rigs full-time, we are still in search of THE BEST material for bus or van conversion insulation. Many people online and YouTube claim materials to be more superior over others, but it’s up to you to at least understand the facts.
1. Rigid Foam: We already covered a lot of the different types of rigid foam including EPS, XPS, and IPO. This is definitely the cheaper option. However, it does have a lower R-value per inch.
2. Closed-Cell Foam: There are quite a number of reasons why we chose spray foam for our walls and ceiling in our 2002 Thomas Built conversion. It has a high R-value, eliminates air infiltration, controls moisture, reduces drafts, improves indoor air quality, and is environmentally friendly and sustainable.
Closed-Cell gives you about 6.0 in. per sq. ft. and completely covers all the nooks and crannies around your bus. They do make kits for a little over $800, but we’d recommend hiring a professional to do it. We had someone come to us and spray foam our bus for $1,000 and it saved us tons of time (and mess). It is more money than rigid foam, but the extra insulation will hopefully benefit you in the long term.
If you are interested in doing it yourself, Amazon does sell DIY kits for between $700-800 for approximately 650 sq. ft. We used about 500 sq. ft. at 2 inches, so factor in that you may need a bigger kit based on the size of your rig.
Some things to consider: We’ve heard a lot of people feel concerned about closed-cell spray foam is toxic. Spray foam can be safe to use within your rig, but you need to ensure that it’s had enough time to fully cure. We suggest getting it installed by a professional or doing your research before trying it yourself to prevent any potential health concerns.
Quick Tips When Finding a Professional: Ask for 1 1/2″ vs. 2″. Let them know you’ll do the cleanup, scraping, taping, and prep work. Some companies may be picky because you don’t have a big enough space. Make it as convenient for them – you can even offer to drive your rig to another project they’re doing so they can spray it there!
3. Wool Insulation: When installed correctly, wool insulation filters air, improves indoor air quality, and is completely all-natural. In addition, it controls moisture and prevents mold and mildew. As an acoustic buffer, wool has also been proven to absorb sound.
During a build-out of a 2019 Mercedes Sprinter Van, we installed Havelock Wool. Overall, we were happy with the ease of installation. However, the wool does have a bit of an odor and requires a bit of work to cut.
Quick Tip for Installation: Either tear or use share shears to get the batts down in size. The sheets can be split in half and shredded piece by piece versus cutting. Stringing staples across the space between the ribs will help hold the wool in place. Wool should be doubled up on ceilings.
4. Fiberglass Insulation: If your budget is up for it, some people even try denim and fiberglass for their ceiling and wall insulation.
Plywood Application for Walls & Ceiling
Applying the plywood over the bus and van conversion insulation is similar to that for the flooring. You’ll be using thin-layer insulation over another thin layer of wood that goes over the supports of the bus. Then, you’ll apply pieces of plywood over that using more Liquid Nails adhesive. For our ceiling, we saved money by cutting pieces of plywood to size instead of using the tongue and groove style. While it was a lot of extra caulking and work, we really love the look of our ceiling!
Step 6: Bus or Van Conversion Insulation for Windows
One of the biggest losses of heat is from a van or skoolie’s windows. We built custom shades on each window in our bus conversion that have an extra layer of Reflectix when up.
In the future, we will try and do a full tutorial on how we built these shades. Overall, they have been a lifesaver during extreme temperatures.
Conclusion: Thoughts About Our Skoolie Conversion Insulation
When converting and living in a school bus, you have to take into account that not everything’s going to be perfect. You’re still living in a big metal cage, so heat and cold will come through no matter how much you try to prevent it.
We also do not regret spending the extra money and taking the time to do insulate our ceiling. Temperatures really do fluctuate no matter where you are in the country, so it’s important to plan for that as much as possible in order to stay warm or cool.