By Clayton Houser – Professional van builder (50+ full builds)
Clayton explains why insulation and ventilation decisions should start with the floor – because thickness, noise, and comfort get locked in early – then walks through practical wall insulation and airflow planning so the van stays livable after everything gets closed up.
This is the fifth article in Clayton's Van Build series - you can view the series homepage here.
After layout design, the next thing I like to lock in is the floor because it affects both comfort and how easy the rest of the build is. I’ve found it works better to treat insulation and airflow like part of the early structure of the build. The floor, walls, and ceiling are the shell you’ll live inside. If that shell is cold, loud, damp, or hard to work on later, it affects everything that comes after it.
Once you’ve made the big space decisions (especially bed height and where your key zones will live), you can build a floor and a shell that supports comfort and future changes. Then you’re ready to move into the garage area and systems with fewer surprises.
The Floor Is the Foundation (and It Affects Everything Above It)
I think the van floor is one of the most underrated parts of a build. It impacts comfort, noise, insulation performance, and how easy it is to mount and secure things long term.
It also ties directly to layout decisions from the last post. I’ve seen people lock in bed height, cabinet height, and storage plans – then add a thicker floor than expected and wonder why the van suddenly feels tighter than it did on paper.
If you’re trying to build a van that feels good day to day, the floor is one of the first places I’d build “right” instead of “fast.”
My Basic Floor Approach
I’ve consistently come back to a simple, durable floor stack-up.
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A flat, strong subfloor that gives you a reliable surface for mounting and fastening
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An insulation layer that helps with temperature and road noise
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A plan that accounts for moisture, not just “R-value”
I’m not trying to build a perfect house floor inside a van. I’m trying to build a floor that’s comfortable, quiet, and doesn’t create problems later.
Build a Subfloor You Can Trust
A plywood subfloor gives you a strong, flat platform and makes everything above it easier. The floor is the foundation of the build. It affects everything from comfort and insulation to cabinetry and how you mount things later.
Why I Like Marine-Grade Plywood
Marine-grade plywood is built with waterproof adhesive and fewer internal voids than typical construction plywood. Practically, that means better moisture resistance and less chance of warping or soft spots over time. It also tends to have a more consistent core, which matters when you’re fastening into it and mounting cabinets or gear. For thickness, I typically recommend ⅝” or ¾” – with ⅝” being a great balance of strength and weight in most builds.
The goal isn’t to overbuild the floor – it’s to make it strong, stable, and predictable so everything you build on top of it goes smoother.
Marine-grade costs more up front, but I’ve found the consistency and moisture resistance are worth it for a van floor.
A Clean Process That Works
Here’s the basic workflow I’ve used.
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Template first
Vans aren’t square. I usually make a template and test-fit it before cutting the final plywood. -
Cut and test-fit in sections
I’ve found it’s easier to install the floor in multiple pieces than trying to wrestle one huge panel into place. -
Seal the plywood
I like sealing the underside and edges to help with moisture resistance. The bottom side is the part that’s closest to a metal floor that can see condensation and temperature swings. -
Mount it securely
The point of a subfloor is that it becomes a stable base for your build. I want it fastened well so it doesn’t squeak, shift, or loosen over time.
This is one of those steps where doing clean work early pays dividends for the rest of the build.
Insulate the Floor for Comfort and Noise (Not Just “Warmth”)
Most people think about floor insulation as a cold-weather thing. I think about it as a comfort thing.
A floor can be a major source of heat loss, but it’s also a major pathway for road noise and vibration. I’ve found that insulating the floor well tends to make vans feel more “finished” and less like a loud metal box.
What I’ve Used for Van Floors
For floor insulation, I’ve used 3M Thinsulate AU4002-5 (double scrim). It’s designed for automotive applications, and it’s worked well for the realities of a van floor.
Here’s why I’ve liked it in this application.
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The double scrim layer makes it more durable under compression and friction
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It’s moisture-resistant and breathable, so trapped condensation has a chance to dry out rather than staying wet
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It improves thermal performance in both directions (cold weather and hot weather)
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It helps with acoustic dampening, reducing road noise and vibration
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It’s lightweight and straightforward to install
It’s not the only option, but it’s been a solid option for how I build floors.
A Note on Sound Deadening
Some people go heavy on sound deadening. I’ve found that a little can go a long way, and you don’t need to cover every inch of the floor to get real benefits.
If your goal is maximum quiet, then you should add a sound deadening layer as part of your floor plan. If your goal is a simpler build that is reasonably quiet, then a good insulation layer plus a solid subfloor will make the van both simpler and noticeably quieter.
A Straightforward Installation Method (That Doesn’t Overcomplicate It)
Floor insulation doesn’t need to be complicated.
I’ve used a simple process.
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Prep and clean the metal floor so the insulation sits cleanly
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Cut the insulation to fit the floor contours
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Lay it in place in a way that avoids big gaps
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Install the plywood subfloor on top
One detail that matters is remembering that some insulation can look thick before install, then compress once the subfloor goes down. That can be helpful when you’re doing your headroom math and trying to keep the floor from getting too tall.
Walls and Ceiling: What I Use and Why
When it comes to wall and ceiling insulation, I’ve tried a few approaches, and I’ve learned that the material choice affects more than temperature. It affects how clean the build stays, how easy it is to change later, and how hard it is to service wiring.
Why I Lean Away from Spray Foam
I haven’t liked working with spray-foamed vans. The biggest issue I ran into is that it’s much harder to run wires or make changes later – you end up having to dig it out to get anything done. I’ve also heard concerns about toxicity, and I didn’t find the real-world payoff worth the tradeoffs for the way I build.
Thinsulate vs Wool (What I’ve Seen)
For most of my builds, I’ve leaned toward Thinsulate. It’s clean, it looks good, and if you ever need to remove it – like adding a window later – it’s easier to pull out than something permanent.
I’ve used Havelock wool in a couple of vans, but I’ve seen a problem when it gets wet – it can droop down to the bottom of the van and leave the top half without insulation. It also has a tendency to smell when it’s damp, which isn’t great in a small space.
For me, Thinsulate has also been one of the easiest DIY options. You measure, cut it, spray adhesive, stick it, and you’re done. In most areas I’ll do at least one layer, and sometimes I’ll double it up depending on the build and the space I’m working with.
How Insulation Connects to Wiring and Future Changes
This is also where I think ahead to serviceability. I do insulation before wiring, and then I keep wires between the insulation and the wall panels so the interior stays flatter and the wires aren’t glued into the insulation. If wires run through insulation, you can end up with kinks, and it’s harder to fish a wire later if someone wants to add or change something.
I’ve learned to build in a way that can come apart. I’ve worked on vans where everything was glued and nailed, and upgrades turned into break-and-rebuild jobs. I’d rather plan for change while the van is open than force someone into a teardown later.
Airflow Planning Before You Close Up the Walls
Airflow and ventilation are part of the same “shell” decision-making – once the insulation and panels go in, upgrades get harder.
Start With a Roof Fan – Plan for the Possibility of A/C Later
A roof fan (like a MaxxAir) can be a great starting point for a lot of builds. What I’ve seen happen, though, is people live in the van for a while and realize they want real A/C. That upgrade can get painful fast if the van wasn’t built to come apart cleanly.
Don’t Build Yourself Into a Corner
This is where insulation work and build methods intersect. If things are glued, nailed, and sealed in a way that makes panels and headliners hard to remove, even a straightforward change can turn into a teardown. I’ve seen people who wanted to go from a roof fan to A/C and ended up having to break apart finished areas because there wasn’t a clean way to access what they needed.
What I Do to Future-Proof (Without Installing Everything Up Front)
If I think there’s any chance A/C could be added later, I plan for it while the van is still open. One example is running heavy-gauge wire up into the headliner area and coiling it near the fan location, even if the build is only getting a MaxxAir fan at first. I also like running wires between the insulation and the wall panels so the interior stays flat and future wire runs are still possible.
If you don’t end up adding A/C, no harm done. If you do, you’ll be glad you planned for it before everything was finished.
What Comes Next
After you’ve made your layout decisions and built a floor and shell that support comfort, the next step is thinking through the garage space under the bed.
That’s where most systems end up living, and it’s where build decisions start to interact in a real way – electrical, plumbing, storage, and access all competing for the same space.
That’s what I’ll cover next.
Frequently Asked Questions About Insulation and Ventilation in Van Builds
1) What part of a camper van should I insulate first?
I like starting with the floor. The floor affects comfort, noise, and how the whole build sits. It also ties directly into headroom and bed height decisions.
2) Why use a plywood subfloor in a camper van instead of building directly on the metal floor?
A plywood subfloor gives you a flat, strong surface for mounting and fastening. It makes the rest of the build easier and helps avoid squeaks and shifting over time.
3) Should I template the camper van floor first?
Vans aren’t square. I’ve found templating and test-fitting before cutting final plywood saves a lot of frustration and helps you get a tighter fit.
4) Why seal the plywood subfloor of my camper van?
Moisture is real in vans. Temperature swings and condensation happen, and I’d rather protect the plywood from the start than hope it never gets damp.
5) What substrate should I use on my camper van floor?
Marine-grade plywood is built with waterproof adhesive and fewer internal voids than typical plywood, which helps with moisture resistance and consistency. It costs more up front, but I’ve found it’s worth it for a van floor.
6) What thickness plywood should I use for a camper van subfloor?
I typically recommend ⅝” or ¾”. In most builds, ⅝” is a great balance of strength and weight.
7) What insulation do you use for camper van floors?
For floor insulation, I’ve used a 3M double scrim Thinsulate (AU4002-5). It’s designed for automotive use and has worked well for the realities of a van floor.
8) Do I need sound deadening if I’m insulating a camper van floor?
Not always. Sound deadening can help, but I’ve found insulation plus a solid subfloor already makes a noticeable difference while keeping the build simpler..
9) What insulation do you use on camper van walls and ceilings?
In most builds, I’ve leaned toward Thinsulate because it’s clean, easy to work with, and easier to remove later if you need to change something (like adding a window). For DIY work, it’s one of the simplest options I’ve used – measure, cut, spray adhesive, stick it, and you’re done.
10) Why don’t you like spray foam for camper van walls?
I’ve worked on vans that were spray foamed and found it made changes much harder because you have to dig it out to run wires. I’ve also heard concerns about toxicity, and I didn’t feel the tradeoff was worth it for the way I build.
11) Should I use wool insulation in my camper van?
I’ve used Havelock wool in a couple of vans, but I’ve seen it droop when it gets wet, leaving the top half without insulation. I’ve also noticed it can smell when it’s damp, which matters in a small space.
12) How do you route wires relative to camper van insulation?
I insulate first, then keep wires between the insulation and the wall panels. It helps keep the surface flatter and avoids wires getting glued into insulation, which can create kinks and make future wire-fishing harder if someone adds or changes something later.
13) How does ventilation relate to insulation in a camper van build?
Insulation helps you hold temperature. Ventilation helps you manage moisture and comfort. I think of them as a pair – especially if you want a van that feels good in real life, not just parked in a driveway.
14) Should I plan for A/C even if I’m not installing it right away?
A roof fan can be enough for a lot of builds, but some people live in their vans for a while and then decide they want A/C. If there’s any chance you’ll want it later, the easiest time to plan wiring paths, space, and access is before everything is finished and closed up.
