Below, I will outline step-by-step how to insulate the inside of a cargo van. If you’re still debating the best materials for insulating a cargo van I have a previous article about selecting the best insulation for van conversion that outlines insulation options and important things to consider in your decision.
Materials Needed for Insulating a Cargo Van
Heavy duty shears (if using Thinsulate or sheep wool.)
Utility knife (if using foam boards.) These cheap ones work the best.
3M Hi-Strength 90 Spray Adhesive for gluing thinsulate, sheep wool and foam board to van walls, ceiling and floor.
Loctite PL300 Foamboard Adhesive to glue foam board layers together. Foam board to foam board, otherwise use the 3M spray above.
Spray foam to fill in thermal bridges and gaps after installing your primary cargo van insulation.
How to Insulate the Inside of a Cargo Van
Van insulation is a lot like a new roof- it’s expensive, it takes a bit of time, and when it’s done no one even knows you have a new roof. However, getting this step right is going to set you up for comfort in your van so it’s incredibly important.
Installing cargo van insulation should take 1-2 days, depending on what material you use and how serious you are about filling every nook and cranny (PS you should be very serious!! Remember that thing about thermal bridges?)
Best Way to Insulate a Van Floor
Cut strips of ½” XPS foam board to fit between the ribs on the van floor.
Glue each strip directly to the metal van floor using 3m Hi-Strength 90 Spray Adhesive. This adhesive works best if you spray both surfaces and wait a few seconds for the glue to tack up before pressing the foam board securely onto the van floor.
Next, cut a ½” or 1” piece of XPS foam board (depending on how much interior headspace you require, you may need a thinner layer of insulation) to fit the van floor. You’ll likely need 2 or 3 full sections of XPS foam board to cover the entire floor.
Glue your top layer of XPS foam board to your first layer with Loctite PL300 Foamboard Adhesive. Add some weight (extra dumbbells, laundry soap, canned goods, your little brother, etc) to the top layer of foam board to help both layers adhere while the adhesive cures.
Note: if you plan to build a camper van with shower consider where that will be and do not insulate that area if you’ll be tight on headspace. The shower pan will add 2-3 inches to your floor so by skipping the insulation in that area only you can reclaim some height.
How to Insulate a Cargo Van Wall
Next, onto the walls! This is the most difficult part because of how many tight spaces there are.
Thinsulate (or sheep wool)
If you are using Thinsulate, cut large sections to fit the mid wall. Adhere the white/fluffy side to the metal using 3m Hi-Strength 90 Spray Adhesive. First, spray the white side of the Thinsulate and then spray the metal. Let the glue tack up for ~30 seconds before pressing the Thinsulate against the wall.
Next, cut smaller sections of Thinsulate to fit the small nooks and crannies. Remember that Thinsulate works best when it’s fully expanded, so place it in each cavity without compressing it.
If you are using sheep wool instead of 3M Thinsulate van insulation you’ll want to use twine instead of spray adhesive. String the twine through the holes available in the sheet metal and tuck the sheep wool behind it.
If you are using foam board then cut as many large sections as you can to cover the wall surface. The thicker the foam board the less interior space you’ll have, but the more temperature regulation you’ll have.
Next, cut smaller sections to fit any gaps or small nooks and crannies.
Regardless of whether you’ve used Thinsulate or foam board your final step is sealing any gaps (which will become thermal bridges) with Spray foam. This stuff works much better if you’ve really shaken the can first.
Best Way to Insulate a Cargo Van Ceiling
There are two primary locations you need to install insulation on your ceiling: the flat surfaces in between the ribs, and inside the ribs.
Flat surfaces can be covered with foam board. XPS will flex slightly to the contour of the van but polyiso will be more rigid and too difficult to use for the van roof. Find some long pieces of lumber that you can wedge between the floor and ceiling to hold the ceiling insulation up while the glue cures.
Foam board has a higher r-value (meaning it’s a better insulator) than Thinsulate or sheep wool so it’s ideal for the ceiling because this is where most of your heat transfer will occur.
Thinsulate or Sheep Wool
Ribs can be stuffed with Thinsulate or sheep wool, or you can use spray foam to insulate the cavity. It’s important that you do not skip this step because the ribs act as thermal bridges and will create a gap for heat transfer through your van ceiling.
The easiest way to get insulation in the van roof ribs is to string twine through the rib from one side to the other. Then, tie the twine to the end of your insulation and pull the opposite end of the twine so that it pulls the insulation into the rib. A tool like this fish tape will get the job done even faster, but it’s not necessary.
Insulating a Cargo Van Headliner
The best way to insulate a van headliner is without removing it. While it can be removed, it requires you to find 6 million different pins (I’m exaggerating… kind of) and unfasten them without breaking them. It’s mission impossible.
Instead, use Thinsulate, sheep wool or spray foam and gently bend the headliner down so you can stuff insulation behind it. You’d be shocked how much heat comes through this area on a sunny day- you absolutely want insulation here.
How to Insulate the Inside of a Cargo Van Door
The easiest way to insulate van doors is to remove the plastic panels. They’re usually held on with plastic pins that are barbed at the end. Gently pulling towards you will release these, but be careful not to twist or pull too hard because you can break the plastic (if you do, most local hardware stores, like ACE, sell replacement pieces in the same section you can buy bolts and screws.)
One very important thing to remember when insulating your van doors is that they’ll have water in them at some point. This is normal. When it rains water can get in through the window or other seals. Doors have weep holes in the bottom to allow this water to drain so you do not want to plug those holes with your insulation.
Use Thinsulate, sheep wool, or foam board to fill the cavity. You can also use spray foam but make sure there are still ways for water to drain to the bottom of the door and out the weep hole.
Planning a van build?
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Written by Claire Fleming
I’m a travel enthusiast who spends half the year in my self-built camper van with my dog, Oscar, and the other half at my home in Raleigh, North Carolina or on international adventures.