Best Budget Van Insulation: Still Original After 8 Years

It's a NASA-quality radiant heat reflection product from a small company whose name I can no longer find: a pink foam with a reflective face on one side and an adhesive on the other. The sticky side goes straight onto the inside of the van wall and ceiling.

It has worked really well for us. I can't give you a lab R-value for it, and I'm not going to invent one. What I can tell you is that it's been in the van for eight years of black-van summers and Colorado cold.

On the side walls we added polyiso board as an extra layer. Wall panels cover all of it. Very little of the van has changed since the 2018 build: small tweaks here and there, nothing big.

The van came with a plastic cargo floor, which adds a little insulation on its own. Under it, on the metal floor, we laid Reflectix. The metal floor has ridges, so there are air gaps between them. It helps a little, but a floor is the wrong place for a reflective material. Reflective insulation works by stopping radiant heat, and the sun never hits the underside of a van, so there isn't much radiant heat down there to stop.

No spray foam, no Thinsulate, no rigid foam under the floor, and no rust-proofing treatment on the bare metal before the insulation went in. After eight years there's some surface rust on the suspension and none on the body. That's one van, so we're not telling you to skip rust-proofing; we're telling you what happened on ours.

A van makes moisture all day from breathing and cooking, and insulation can't do anything about that. Moving air can. We run two roof fans and T-vent windows on both walls, and we've had them since the build. If you're planning insulation, plan the ventilation in the same sitting. How we set up our fans →

A synthetic fiber batt that doesn't absorb water, which is why it's popular for van walls. It's soft, so it fills around ribs and irregular cavities. SM600L is rated R-5.2 at its full 1.65" loft. Spec It costs more per R-value than rigid foam and loses effectiveness when compressed, so it doesn't belong under a floor.

The highest R-value per inch in the rigid foam family, around R-6 per inch. Spec It's the extra layer on our side walls, where the surface is flat enough for a board. It's cheap per R-value but only sits well on flat surfaces, and every edge has to be sealed or the gaps become cold spots and places for condensation to collect.

Hardware-store cans are for filling gaps and seams, not for insulating whole walls. Full spray-foam jobs are done by installers and are hard to undo. On older vans with surface rust, people prime the metal first so foam doesn't seal moisture against it.

House fiberglass holds moisture, and a van produces a lot of it. Held against a metal body, that means mold and rust. This one is general building practice rather than our experience, but it's the one material almost every van builder agrees on.

Something rigid that won't crush under foot traffic and storage weight, and that resists heat moving by conduction, because that is how a floor loses heat. Ours is Reflectix on the ridged metal floor, under the van's plastic cargo floor. It helps a little, but reflective insulation mostly stops radiant heat from the sun, and the sun never reaches the underside of a van. Soft batts like Thinsulate compress under load, so they're the wrong choice there too.

It has been for us on the walls and ceiling, behind the wall panels, where the sun hits the van hardest. It does the least where there's little radiant heat to stop, like under a floor. Judge any reflective product by where it will sit, not by the number on the package.

Usually not, and putting one on both sides of the insulation traps moisture with nowhere to go. What matters more is ventilation: a fan and an open window on the far side of the van move the moisture out before it settles on cold metal.