Comparing van insulation options

We chose to insulate our van with Thinsulate and Low-E reflective foam/foil. We could have chosen foam, fiberglass, wool, or even recycled jeans instead. Here’s the pros and cons comparison we created so you can choose the material that’s best for you.

This is a long post. Want to jump to a specific section? Here’s the index:

What's insulation for?
    Heat insulation
    Noise insulation
Comparison of insulation types
    Spray Foam
    Rigid Foam
    Flexible Foam
    Glass bead paint
    Radiant barriers (Reflectix, Low-E)
Noise insulation
    Constrained Layer Dampener
    Closed Cell Foam
    Mass Loaded Vinyl
Other considerations
    Mercedes' factory insulation package
    Climate Control

What’s insulation for?

Insulation is supposed to stop or slow down the flow of heat or noise.

An empty Sprinter is a big metal oven in the summer, trapping and amplifying the heat of the sun. During the winter it loses its heat quickly to the outside. The climate control in the dash can’t keep up with the massive area of the van.

It’s also loud. Sound enters through the floor and wall panels and bounces around inside the van. There’s some factory sound damping stuck to the wall panels, but the van can still sound like being inside a big oil drum.

Insulation makes sure the heat stays where it should – inside or outside the van – and dampens the sounds like road noise to make the van quieter. You often need different types of insulation for heat and sound.

Stopping heat movement with insulation

Heat moves through conduction, convection, and radiation.

Think of the situation where the sun is shining on the outside of your van.

  • Conduction is where the heat moves through a substance. The van’s metal body is a very good heat conductor. Heat in one part of the body spreads to other places fast. The heat from the sun gets spread from the outside to the inside of the metal van walls by conduction. You stop conduction by making a thermal barrier. In other words, you use a substance that does not conduct heat well (some foams, for instance) to block the transfer of heat.
  • Radiation is where the heat is given off by a surface. You can put your hand near the inside van walls on a hot day and feel the heat being given off – radiated – even without touching them. The sun heated up the metal and now that heat is being re-radiated inside the van. Again, anything that blocks the heat from being radiated will be a good insulator.
  • Convection is where the heat is transported through the air. Once the sun’s heat gets radiated inside the van, it heats up the air in the van. Warm air is lighter, so it rises and pushes cold air down. That creates air currents to move the heat around inside the van. You stop convection by filling gaps so the air can’t be transported. If you stop air from moving close to the hot metal on the inside of the van, it won’t be able to warm up from the radiated heat and then move that heat inside through convection.

Insulation is measured by how good it is at preventing heat from getting through. The unit of measurement most people use is the R value. The R value measures how well a material stops heat from being conducted through it, but not how well it prevents convection or radiation.

How does noise move?

Sound waves hit the metal walls of your van. The walls flex. The flexing recreates the same sound on the other side. You also get some noise transferred from the road through the suspension and into the vehicle frame. That makes the wall panels flex (resonate) and create the same noise inside the van.

So to stop the sound, you need to stop the panels flexing as much as you can (“dampen” them), and then muffle any remaining sound energy they produce.

The dampening is done by sticking relatively heavy butyl rubber and foil pads on any flexy metal surfaces. The muffling is done by using a layer of closed cell foam and – if necessary – a layer of free-floating heavyweight material such as mass loaded vinyl. explains this in a bit more detail. Just remember, you aren’t necessarily going for the same level of soundproofing as their products will offer. Also, some of your heat insulation products will help with noise insulation too, whereas others will not.

Comparison of insulation types

OK, here’s the bit you wanted to know all along, before we made you read through the the physics lesson.


A synthetic material made of polyester and polypropylene strands that puff up and trap air between them. The automotive version is slightly different to the type of Thinsulate you find in coats and gloves, but it works on the same principle. The automotive Thinsulate is sold primarily as an acoustic insulation (noise reducer) but it also has a pretty good R-value.

Thinsulate comes on a 60″ wide roll. That makes it ideal for a van, because the width of the roll works out just right for the width of the ceiling panels. Because it’s so wide, it’s also possible to span the large panel sections in the back of the van without needing joins. Joins are bad in insulation because they are a place where air/heat/noise can flow through.

Mostly you’ll want to glue Thinsulate in place with contact adhesive (like 3M 90). The Thinsulate comes with a scrim (a black non-woven fabric layer) on one side. It doesn’t seem to matter which side you spray the glue on, and the black layer looks better and has less loose strands than the white side.

Contact adhesives need to dry before you join the two pieces. Once you do join the pieces, moving them is hard. That means you have to cut and place the Thinsulate carefully.

Thinsulate also works well in the ribs and other less accessible areas of the van body. You can pull a long strip through the metal ribs using a wire fish, then it expands to fill the gaps.

Thinsulate and LowE insulation

People will often use a foil-faced foam product (LowE or Reflectix) in combination with Thinsulate. The LowE gets taped on to the ribs inside the van before the interior finish panels are put in place. Because the Thinsulate doesn’t completely fill the voids in the walls, the LowE has the air gap that it needs to do its job properly.

R value: Just over R3 per inch (5.2 for the 1.65" SM 600 automotive Thinsulate)
Cost: $1.80/sq. ft from Hein on the Sprinter forum or his eBay store. He's also selling it on Amazon. 
Ease of use: High.
Hazards: Relatively inert substance. Some small fibers will come off as you cut the roll of Thinsulate to size with scissors. It needs to be glued in place, and that glue (3M 90 or similar) is unpleasant. Wear a respirator.

Spray foam

Spray foam typically starts life as two liquids. When they’re mixed in the spray nozzle, they make a sticky foam. The van walls and ceiling are coated in anything from 1/2″ to 2″ of foam.

There are many companies that will spray your van for you. Alternatively it’s possible to buy cans of “great stuff” foam but it takes a lot of aerosol cans to foam a van. Instead, you can get large-size canisters with external spray nozzles. Those canisters give anything from 200 to 600 sq.ft of coverage.

Spray foam is not good to use inside doors or any other areas with moving parts because it’ll glue them up. You also have to plan your build and run wiring (or at least wiring conduit) and any other in-the-wall elements before you foam.
Spray foam will cut air-based noise levels, but won’t help much with damping structural noise. There are some concerns that foam can warp the van walls. The exact mechanism isn’t clear, but heat/cold and changes in elevation tend to make it worse.

If you are thinking of doing this yourself, remember to get a closed cell foam rather than an open cell one (which can hold water). Some people suggest getting the slower-expanding foam because it’s less likely to make the wall panels “pop” or bow.  Mask off EVERY surface that you don’t want foam on. It’s sticky and very hard to remove when it sets. If you end up spraying it so thick that it sticks out beyond the wall, you can cut it off with a saw.

  • Foam-it-green is around $650 + $150 delivery for 600sq. ft at 1″ thickness. 
  • Tiger Foam costs $600 + $150 delivery. They also make a slow-expansion option. 
  • Touch ‘n’ Foam is $730 at Lowes, with free in-store pickup
  • Dow FrothPak is $660 + $100 delivery
Commercial companies’ costs seem to vary widely.
Spray foam
R value: R6 to R7 per inch thickness.
Cost: Around $1.20/sq. ft DIY, $0.50 to $1.50/sq. ft commercial.
Ease of use: Medium. Requires masking of entire van before application. Requires protective clothing and respirator. Requires some skill to install well. Ambient temperature must be in a suitable range.
Hazards: Requires full body protection when applying (messy clean-up) and off-gasses as it dries. Wear protective gear – a respirator (get the right size) and a tyvek coverall

Rigid foam (Polyisocyanurate and Styrofoam)

Polyisocyanurate (RMax brand) and Styrofoam (RTech brand) insulation comes in rigid sheets, from 1/2″ thick to 2″ thick. The material has a very good R value for its thickness and weight.

The type of styrofoam used in this insulation is not the same as packing material. Instead it’s extruded. It’s much better to work with because it doesn’t crumble into tiny beads.

The sheets can be bent to shape for the walls and ceiling, but they might need scoring in order to fit around tighter radius bends.

People tend to glue the polyiso boards in place with spray foam. The boards can squeak if not attached properly. The boards are hard to fit in some panel areas where the internal metal overlaps the hole. They are often used in conjunction with either spray foam or Thinsulate in the metal ribs and other inaccessible areas of the van. It might be worth using spray foam to create a seal around each board so that moisture cannot condense against the van wall behind the foam boards.

One potential benefit to polystyrene board mentioned on the Expedition Portal site is that PolyIso can lose R value at lower temperatures, whereas the polystyrene does not. The same poster also recommends Vulkem polyurethane adhesive for polystyrene sheets because it remains flexible.

Rigid Foam
R value: Rmax PolyIso is R6.5 per inch. R-tech polystyrene is R3.8 per inch.
Cost: Rmax is $1.00/sq. ft for the 2" thick (R13.3) material. R-tech is $0.68/sq.ft for the 2" thick (R7.7) material.
Ease of use: Medium. Needs cutting to shape and fitting into awkward panel areas. Must be glued in place.
Hazards: Very few installation hazards. The board can be cut with a knife or a special foam board circular saw blade. The foam boards tend to be glued in place with spray foam (Great Stuff or similar) which can be messy and isn't good to inhale. It's possible for condensation to form between the foam and the metal van wall if the boards aren't sealed around the edges with spray foam.

Flexible foams (EPDM, Melamine)

An alternative to rigid foam products is foam sheets made of various materials such as EPDM or Melamine. These are typically open cell foams that have been treated with hydrophobic agents, or closed cell foams with more flexibility than the PolyIso or Styrofoam versions. They can often be rolled up for shipping. That also means they’ll fit to van walls better.

Aerocel is a closed cell EPDM foam designed for HVAC duct insulation. Graphite Dave on the Sprinter forum has used the 1″ thickness foam in his recent build. It has a claimed R value of 4.1. It’s not clear exactly how this differs from other neoprene foams such as those offered by

BASF Basotect and Polymer Technologies’ Polydamp hydrophobic melamine foam are both open-cell foam that’s treated to make it water resistant. It’s intended primarily as a noise damping product, but it also has pretty good thermal conductivity. It’s very flexible. Sound Deadener Showdown uses this type of product in their van insulation projects.

Flexible Foam
R value: ~R4 for 1" of either EPDM or hydrophobic melamine. 
Cost: $4.57/sq.ft for 1.5" EPDM; $8.25/sq.ft for 1.5" thick hydrophobic melamine. 
Ease of use: High. Flexible, easy to cut, easy to glue in place. 
Hazards: Working with the products should produce minimal dust.Melamine foam is formaldehyde based, if that worries you. Attaching with contact adhesive means you should wear a respirator.

Recycled denim

This insulation material is cut up, fluffed up jeans, treated with mould, fire and insect inhibitor chemicals. It’s supposedly green because it’s recycled, but that’s not necessarily true. I’d also be concerned about the chemicals.

It’s relatively easy to work with. It comes in batts that you can cut to size/shape, although it doesn’t cut particularly cleanly so you might find it hard to get gap-free installs. It bends and deforms so it’s easy to put in difficult panel spaces.

The one big problem with recycled denim is that it’s not hydrophobic. In other words, if it gets wet it’ll soak the water up and then it will need to dry out. That means if any water condenses or spills against the van walls, the insulation will encourage rust. Even if you put a vapor barrier inside the van, there are weep holes in the cavities where water can get in.

Personally, this stuff scares me. It feels like a rust accelerator. If you live in a completely dry climate and if you have filled all the holes behind the side trim panels in your van, you might just be OK. Everyone else should probably not use it for van insulation.

R value: R3.3 per inch (R6.7 for 2" thick batts)
Cost: $1.12/sq. ft at 2" thick
Ease of use: Relatively high for van use, but you'll have to piece batts together for the wider panels.
Hazards: Low-itch for install. Some questions about the added chemicals though.


Like denim, this product is a “natural” material. Wool clothes are warm even when they are wet, so you’d think this was a great insulator, but wool clothes do hold water. Wool insulation does too. That means it has the same concerns as denim. As a positive, it’s pretty hard to set wool on fire, especially with the Boron flame retardant they add.

This stuff is not cheap. It makes Thinsulate look inexpensive. It is also mostly available in 3.5″ and 5.25″ thicknesses for residential installation. You’re likely to have to cut the 3.5″ thickness down to use in a van because the walls aren’t that deep consistently. There’s no point “stuffing” it in because compressing insulation actually reduces its R value rather than improving it.

I have similar concerns about this product to the ones I mentioned about denim. The Good Shepherd site specifically mentions the absorbtive properties of wool as a positive point. That might be true in a residential timber frame house, but it’s not so wonderful in a steel van.

R value: 3.7 per inch (R13 for 3.5" batts)
Cost: $2.19/sq. ft
Ease of use:Relatively high for van use, but you'll have to piece batts together for the wider panels.
Hazards: Getting too full of yourself for using such an environmentally sound material. Seriously though, wear a respirator when installing it because of the small fibers.


This is what houses are most often insulated with. It’s also used by a couple of the professional van upfitters. Just remember, fiberglass is a skin, eye and lung irritant. Long term exposure can cause respiratory problems. How well will you be sealing it away behind your walls? Also, it holds water.

Although you can get it in multiple widths, most fiberglass batts are 15″ wide to fit in to residential construction. You’re going to have to join several widths together inside the van cavities. Gaps between the batts are an opportunity for heat gain/loss.

R value: R3.7 per inch (R13 for 3.5" thickness)
Cost: Around $0.35/sq. ft at 3.5" thickness
Ease of use: Relatively high for van use, but you'll have to piece batts together for the wider panels.
Hazards: Respiratory problems. Eye, skin and lung irritant. Long-term exposure (every time you use the van) can cause lung disease.


A space-age material that is super-light, hydrophobic, and has a super-high R-value. It’s also super-expensive. If you can get over the damage to your wallet, most types you can buy produce dust when you handle them, so they may create some installation issues.

Now you can buy it in blanket form to use for insulation.The blankets are flexible, so if you only have a thin space in which to put insulation, it’s potentially a good option.

For the “green” buyer who is considering denim or wool, check out Aerogel instead. It holds Silver Cradle certification for its low environmental impact during manufacturing and its low ecological impact. The blanket form is made of silica nanopores in a Polyester and Polyethylene batting matrix.

  • Thermal Wrap is an 8mm thick non-dusty product.
  • Spaceloft is a 10mm thick dust-producing product.  
  • There’s an eBay seller of Spaceloft aerogel charging $25 per linear foot 57” wide (4.75 sq.ft)

Technical side note: I have some issues with the hype. Thermal Wrap has a thermal conductivity of 0.023W/mK. This is the same as the thermal conductivity of PolyIso insulation. Spaceloft has a thermal conductivity of 0.014W/mK – so much better insulation, but still a very high price. In other words, although the original aerogel product has a very high R value, the blanket-based products might not be super-wonderful.

R value: Spaceloft is claimed ~R10 per inch. Thermal Wrap is probably closer to R6 per inch.
Cost: Spaceloft is $5.25/sq. ft on eBay. Thermal Wrap is $9.00/sq.ft from when bought in 40' lengths.
Ease of use: High. Cut with scissors or a knife. Glue in place with spray glue.
Hazards: Dust inhalation during installation and afterwards during use.

Glass bead spray-on insulation

The jury seems to be out on the benefits of glass bead rubberized external spray-on insulation. Its best use seems to be on the roof of vehicles which are constantly exposed to hot sun, such as school buses. The cost-benefit probably isn’t there for northern latitudes.

Because of the dubious claims, I’m not even going to give an R-value or cost per sq.ft comparison here.

Reflectix, LowE, other foil-faced foam/bubble-wrap radiant barrier products

The R value of the foil faced products is terrible. Probably less than R=1. But that’s because they aren’t designed to be used like other insulation materials. If you just stick them to the metal panels of your van, they won’t do much good. However, if you leave an air gap, they use that air as part of their insulation.

R values measure conduction. Foil-faced products work more through reductions in convection and radiation. They function as a radiant barrier.

The manufacturers claim pretty amazing R values, but they are approximations based on a residential setting with no air movement and a large air gap. In a van, if you use a foil faced product in combination with other insulation types, it’s helpful, but not R8 helpful. Just make sure it has an air gap in order to do its thing.

There are several similar products.
  • Reflectix is bubble wrap with aluminum foil faces. Some people complain that it squeaks after installation. It’s also not so good for under-floor use because the bubbles don’t support as much weight as the closed cell versions.
  • Low E/EZ Cool is a closed cell foam with aluminum foil faces. The closed cell foam resists compression and works well under flooring.
  • Prodex is another brand of the same type of stuff. They have bullshit claims of R16 for their product, which puts me off. You will NOT see that R value in a Sprinter install.
  • Remember to also buy foil tape. Get good quality high temperature tape because it’s going to be used in hot places in the van. You will need a lot of it (probably 3 times the length of the foil roll you buy) for an install in a van. If you are gluing it on, you’re missing the point.
Radiant barrier
R value: Around R0.67 for the base material, but its reflective properties increase that number. For instance, LowE claim R3.8 for a situation similar to a Sprinter install. Do not believe the highly inflated values for this type of product. It needs an air gap to work properly.
Cost: Reflectix = $0.48/sq.ft. LowE = $0.46/sq.ft
Ease of use: High.
Hazards: Other than potentially cutting yourself on the edge of the foil, very few hazards either with the install or during use.


Yes, even humble carpet has an insulation value. The R value varies between R0.5 for 1/8” nylon continuous filament level loop, 24oz/sq. yd and R2.2 for 1/2” wool spun yarn plush finish 43oz/sq.yd. So, adding that purple shag pile carpet to the walls and ceiling of your van for a ’70s look does also have some insulating value.

Sound insulation materials

There are no end of opinions about how to reduce sound levels in a van. One resource that comes up time and time again in conversation is the site. They recommend a specific 3-part approach. It’s slightly different for vans than for cars.

CLD layer (Constrained Layer Damper)

This is the layer that stops panels from resonating. To do that, it has to absorb the noise energy and convert it to heat energy. That means adding a semi-rigid mass to the panels. Thick, sticky rubber with a foil coating does the trick quite well.

The better quality CLD materials are butyl rubber rather than bitumen/asphalt based. They come with a foil face and an adhesive backing. You need a 1″ roller to install them properly and make sure they’re properly adhered to the metal walls, roof and floor. We used Reckhorn ABX 80 Mil thick. You can also get Reckhorn in a 100 Mil thickness. The hexagonal pattern on the foil even matches the original Mercedes dampening pads.

Other manufacturers include Dynamat, FatMat, Hushmat, RAAM Mat, B-Quiet, and Armaflex. However, we found that Reckhorn was the cheapest at the time we bought it, partly because Amazon was offering free Prime shipping on the Reckhorn. Now Amazon have moved to offering a product by Noico as their Prime deal instead.

The SoundDeadenerShowdown site suggests that you only benefit from 25% coverage with butyl material. Any more, and you’re adding weight for very little additional noise damping. There were some areas of the van though, like the rear wheel wells, where we did 100% coverage. Gravel thrown up from the road hardly makes a sound now, whereas it was very loud beforehand. The SoundDeadenerShowdown site also has a specific entry for camper vans, where they suggest using thinner butyl rubber sheets and covering 100% of the wall area.

Closed Cell Foam layer

Designed primarily to prevent squeaks and rattles, this layer also has a marginal heat insulation role. The closed cell foam isolates the MLV layer (below) from the walls and stops wall and door panels from rattling against the metal van walls.

In most places, our walls already had a layer of LowE foil-faced foam as part of the heat insulation process. That served as a great CCF layer for sound insulation too.

We also bought a 50′ roll of 1/8″ thick 2lb polyethylene closed cell foam from FoamByMail. It’s non-absorbent, durable, and cuts really easily with scissors or a knife. Mostly, we used it as padding under our automotive tweed fabric wall covering, but the offcuts were also very useful in some locations round the van to use as a sound damping/rattle prevention layer.

MLV layer (Mass Loaded Vinyl)

Mass Loaded Vinyl is used to block the remaining sound waves as they travel through the air. Since most of the sound is coming from the underside and sides of the van, this layer is normally only applied on the floor and lower walls.

The MLV layer has to be isolated from the vehicle walls/floor in order to work properly. It can either be hung as a sheet, or suspended on a closed cell foam layer. If you hang it as a sheet, it’s likely you can use the wall panel screws/bolts to hold it in place.

For our van, we used Elephant Bark 1/4″ rubber (also called Stall Mats) as an MLV-type layer on the floor. We isolated it from the stock wooden van floor using a layer of LowE foil-faced closed cell foam. The full stack of materials gives us a good combination of heat and sound damping.

On the walls, we used DB2-4walls. It’s a .75lb/sf. product, 1/8″ thick. We didn’t use it throughout the van, but we did put sheets of it behind the door panels before we re-applied them. 

Other things to think about

What about ordering Mercedes’ insulation package?

Don’t bother. Really. It’s an expensive option and it isn’t useful for either sound or heat insulation. Here’s a post by AKCub on the forum with pictures of what you get for your money when you order the X12 Crew Heating & Insulation Package. It’s only on the lower half of the wall panels, it doesn’t cover the entire panels, and it’s 1/4″ thick foam. Not much R value there.

Insulation and rust

Vapor barriers are used to stop condensation from forming in the insulated area of houses. The barrier either stops moisture from crossing at all, or “breathes” by letting moisture out of the building but not letting it in.

In a van, you already have a pretty good vapor barrier. It’s the metal walls, floor and ceiling of the vehicle. Adding another barrier inside the van means the insulation has no way to dry out if it gets wet. The general concensus appears to be not to try and make a vapor barrier on the inside of the van. If you’re using a foil-faced product, that can do a pretty good barrier job when it’s taped up, so you might want to make sure there’s still the potential for air flow around it.

Newer Sprinters are sprayed with anti-rust wax on their lower panels inside the van. They also have drip holes in the bottom of the walls for moisture to escape. Both of those things are necessary because condensation can easily form inside the van. Also, the plastic body trim panels are held in place with clips that poke through holes in the sides of the van. Those can leak in the rain. Before you insulate, you might want to seal the holes around the trim panel clips. You might also want to make sure you do not accidentally block the drip holes in the bottom of the walls. If you are gluing insulation in place, or spraying foam, it’s not likely to stick to the anti-rust wax.

Metal filings from drilling and cutting holes will quickly rust. If they’re left in the van walls or the floor channels, they’ll attack the paint and then start rusting the panels. Make sure you vacuum up any swarf after drilling, filing, or cutting. Also, be sure to prime any holes you make so they can’t rust.

Insulation is pointless if you leave the windows unshaded

Don’t forget that the van windows are probably your biggest source of heat gain/loss. They are single glazed, and massive. Most of the heat gain or loss through the glass is in the form of radiation. The foil faced foam insulation materials are great to counter that. They are thin, flexible, clean, strong, and can be held in place with magnets or snaps.

Climate control will work better if it’s only heating the cab

If you hang a curtain, moving blanket, or other barrier behind the front seats, the heating and cooling from the dash vents won’t have to work so hard, and it’s more likely that you’ll stay at a comfortable temperature.

35 Replies to “Comparing van insulation options”

  1. My wife and I are just about to buy a 170 Crew 4×4 and I’ve been reading as much about insulation options as possible. This is one of the most well organized resources I’ve come across. Well done. Now I just need to find/buy a sprinter, order some supplies, and get to work.

    1. Thanks! It took some time to put everything together. Personal preference still obviously has a big role in the insulation decision, but we wanted to make sure people knew the relative merits of the different options. Good luck with your van purchase!

  2. I’m considering using Prodex, instead of ESP lowE, because it’s available in 72″ width and it has a closed-cell polyethylene foam center that might be better. Right now it’s only $.06 more/sf than LowE. Have you ever used or seen the Prodex or any experience with it? The R value claims are ridiculous, but it might be a slightly better product and far less seams to tape, which I wonder about heat and tape failure with time. I’ve seen high temp. tape fail with time.

    1. I think the Prodex would be fine as an alternative to Low-E. I put as much faith in Prodex’s R-value claims as I do in all the other foil-faced products. In other words, it’s all marketing hype. There’s obviously some insulation value but their R-value claims are seriously exaggerated. The Low-E we used also has a closed cell center.

      I’m not sure how much benefit you’ll get from using the 72″ width. We used separate sheets of material for the top and bottom sections of the walls, so the extra width would have been no use to us there. On the ceiling we taped sheets of Low-E perpendicular to the direction of travel so that we could make use of the roof ribs as taping locations and avoid having the insulation droop.

      The tape may fail later, but so far (one year on) ours is doing just fine. We weren’t trying to create a complete vapor barrier, so now that the interior walls are up and holding the insulation in place, the integrity of the tape isn’t quite so important.

  3. During cold weather if you have an insulated van but no HEAT SOURCE, what are you ‘insulating’? Your body heat isn’t going to warm this van up. Even if you use the van heater right after you stop the van even with R5 insulation isn’t this going to lose that heat quickly? I am going under the idea someone would sleep in the van.

    1. You’re right, the heat from the van’s climate control system soon dissipates after you switch the engine off. The windows are a large source of heat loss. That’s why we have an Espar diesel heater installed, and also optionally use a 12v electric mattress pad overnight.

      The diesel heater is highly efficient and keeps the van at a very comfortable temperature. It would *probably* be able to keep an uninsulated van warm, but it would work much harder to do so, and burn more fuel. The mattress pad is a nice alternative when you want to be warm in the van overnight but don’t want to heat the whole interior.

      The insulation is also great the other way round during the summer. It helps considerably in keeping the van cool. It’s also a good noise block. All the large vans are very “boomy” when they are uninsulated. Adding insulation quietens them down considerably.

  4. Thanks for all of your posts! Very useful!

    re: your insulation… just want to clarify, did you go insulate in this order:

    Van wall (outermost metal) > sound dampening like Rattletrap (not sure if you did this) > Thinsulate > LowE > interior wal

    If so, is the LowE something you surrounded all of the Thinsulate with? I’d imagine if so, you maybe cut a few holes in it here and there to let the Thinsulate breathe or are there enough gaps without doing this? Thank you!

    1. Hey Brad,
      We did use a sound dampening layer in some places in the van, at about 25% coverage. I’m not sure whether it’s actually worthwhile if you’re gluing the Thinsulate in, because the Thinsulate does a pretty good job of muffling noise too.

      Then we glued in Thinsulate using 3M 90 spray glue. That goes inside all the voids between the outside van wall and the interior.

      The Low-E goes on the inside of the van, taped up to the interior walls and the ceiling beams. That way you have an air gap in most places between where the Thinsulate finishes and the Low-E starts. That air gap is important for the Low-E to work properly because it has very little inherent R-value.

      We didn’t purposefully cut holes in the Low-E layer, but there are several places where electrical wires or outlets poke through. Some people try to make a vapor barrier by completely sealing the Low-E layer, but that’s really not practical or useful. The Thinsulate “breathes” through the weep holes in the rocker panel at the bottom of the van walls.

      Then we put up our interior walls. They are either 1/8″ or 1/4″ plywood, covered in 1/8″ closed cell foam and a layer of Olefin fabric.

  5. great posts, thanks for sharing! Is your intent with the Low E to reflect heat back into the van to stay warm? I am making a plan for insulation and trying to figure out how to use it between the exterior metal van walls, with an air gap, and the thinsulate to reflect the exterior heat off the van.

    1. Christine, the Low-E works both ways. It helps keep heat out of the van and helps keep it in. In our van, there isn’t much/any air gap between the Low-E and the interior wall panels, so it’s unlikely to be doing such a good job of keeping heat in.

      We used Thinsulate in all the gaps in the van’s metal walls, and then laid the Low-E over the interior face of the metal walls. That left an air gap between the Thinsulate (stuck on the inside of the outermost metal walls) and the Low-E (stuck on the inside metal reinforcement pieces).

      Even though the Low-E is “inside” the Thinsulate, it still reflects heat back to the outside. The Thinsulate reduces the amount of heat that gets through, but then the Low-E and air gap stop the remaining heat from getting into the van. In other words, the Low-E doesn’t have to be the outermost layer in order to do its job.

  6. If I had a dollar for every van conversion website out there…without a doubt, this site is THE MOST comprehensive and unbiased research I’ve come across. Incredible resource! Thank you, I hope I can save enough money to start my own van one day. If I do, I will know where to turn.

  7. I just want to second the notion that you are a rockstar for putting this all together… the whole site, not just the insulation stuff.
    Without a doubt, you are a top resource for van converters!
    Quick question… I have a 144wb passenger van that I just removed the headliner from. I also have a bunch of thinsulate from Hein. When you “fish” the thinsulate thru the long skinny sections, are you spraying the adhesive in before you do that? Or do those sections go without adhesive?

    1. Gee, thanks. I guess I’m the reclusive type of rockstar.

      We didn’t glue the Thinsulate inside the ribs. I don’t think it’s necessary. If you wanted to ensure it stayed in place, a touch of glue at each end should do the trick. Because the 3M 90 is contact adhesive (it has to dry to a “tack” before you place the two sides together), it wouldn’t do a great job of sticking stuff together anyway if you just sprayed it onto the Thinsulate before you pulled it through.

      Have fun inhaling all those fumes! Actually, don’t. Get a proper respirator. Even with the van doors open, the contact adhesive is pretty pungent stuff while it’s flashing off.

  8. Great post but I still don’t understand why everyone uses the low-e material so much. As you correctly explain, it’s a radiative barrier, but when you burry it in a wall or floor, you eliminate all radiative paths and it simply becomes a conduction barrier, which you again correctly point out its terrible performance. The “low-e” portion only works if you have a radiative heat source, like the sun or a hot, high emissivity surface AND an air gap. If the reflective (low-e) foil touches anything it doesn’t work.

    1. Nick, when it’s hot out, the interior of the van walls is also hot. The metal has absorbed the heat from outside and then it re-radiates it to the interior of the vehicle, so there is a radiative heat source. In most areas of the walls and ceiling there is an air gap between where the Thinsulate ends and the Low-E starts. Some people even count the Thinsulate as part of the air gap. So both the conditions (radiative heat, air gap) are met to some degree in the van.

      From a practical real-world perspective, I can say that there is a good temperature differential between the faces of the Low-E when it’s installed. I put my hand in to the air gap above the Low-E in the roof. Much warmer above the Low-E than inside the vehicle.

      There are other spots in the van where we used it more like a closed cell foam for general noise damping. That may have been overkill (there’s cheaper foam out there that can do the same thing) but it works fine for that job too. It’s also great for making window shades. It does a better job than other materials at keeping heat out of the van from the large expanse of glass.

      In the end, it’s up to you whether to use it or not. The Thinsulate does a lot more to regulate the interior temperature of the van than the Low-E does. We chose to use Low-E because it wasn’t too expensive and it would have been a real pain to retrofit.

  9. “The metal has absorbed the heat from outside and then it re-radiates it to the interior of the vehicle, so there is a radiative heat source. In most areas of the walls and ceiling there is an air gap between where the Thinsulate ends and the Low-E starts”

    If you have thinsulate adhered to the inside of the van’s skin it (the van’s metal skin) can no longer radiate. The van’s skin will transfer heat to the thinsulate through conduction, then if there is an air gap after the thinsulate it’s the thinsulate that has the opportunity to radiate that heat. I have no idea the emissivity of thinsulate, if you’re applying it black side in it could be high (black e>>white e). (That’s a good reason to install it black side to van skin, which I recognize is opposite to what I’ve seen almost everyone do- but this is a good reason to do so).

    1. Good point, and we did install it black side out mainly because that scrim looked like it would cause less problems than the “bare” fiber side. Maybe that’s why we’re seeing benefit from the Low-E 🙂

    1. Lyle, we ran a couple of wires before installing the Thinsulate because we knew they’d need to run through gaps in the bodywork that the Thinsulate would obscure. Then we ran some others after installing the Thinsulate. Mostly it was easier to make the Thinsulate work around the wires than to make the wires work around the Thinsulate.

      If we were ever crazy enough to do this again, we’d be tempted to run more of the wires in an accessible raceway rather than behind the walls. If we were doing that, then we’d be doing Thinsulate first, most likely.

  10. First off…thank you for the wealth of information you have assembled and shared on this site. I continue to scour through most of your site and reference it regularly. I have just completed the installation of the Adventure Wagon “RUV Interior Kit” and am really pleased with the results.

    We went from bare 144″ van to a fully finished interior (minus the floor) in just 4-5 days with 2-3 of us working on it during that time. That said…we had lots of discussions about whether or not to “vent” the reflectix layer that sits just behind the finished wall panels. I spent more time than I care to admit covering each/every seam of the reflectix and fully sealing the interior, prior to putting up the panels….this includes each/every hole on the factory metal walls/supports/etc.

    Now, I find myself a bit stressed that I’ve created a vapor/moisture trap! I can easily remove the bottom panels and vent up approx. 1/3 of each wall, and re-reveal the “weep holes”. In your opinion, do you think this would offer enough ventilation? Or…do you think it is worth removing each panel to cut some vents into each piece of reflectix?

    Any thoughts are appreciated. I’d like to wrap this up and put a bow on it before moving on to the floor.

    1. Ah, the double moisture barrier question. I’m sure you’ve read some of the posts on the Sprinter forum about this. The biggest issue is that the metal van walls form a pretty good moisture/vapor barrier, so adding another barrier on the other side of your insulation creates a potential location for moisture to get stuck and fester.

      I have an opinion on this, but opinions are like belly buttons: everyone has one, and most are not suitable for sharing. Here goes though… You probably want enough potential for moisture to get out from the insulation space in the van. That’s probably best achieved through cutting gaps in the Reflectix layer for each enclosed space.

      If nothing else, it’s unlikely to noticeably hurt your insulation potential and you’ll feel better about it longer term!

      By the way, good to hear that the Adventure Wagon interior kit installs well. I’ve been following their progress online and it looks like they have a good system worked out now.

  11. Hello, your web site makes for a fantastic resource! However, I would like to suggest that you not include “rock wool” in your description of fiberglass insulation. This confused me until I had a conversation with Van Haus (which uses rockwool) and looked it up to learn that rockwool is actually made from superheated rock spun into strands like cotton candy and does not suffer from the issues associated with fiberglass. Not unhealthy, doesn’t retain moisture, etc.

    1. Hi Christopher, I’m glad you’ve found this useful.

      I chose to place rock wool in the same category as fiberglass because both are classed as synthetic vitreous fibers. And (per the CDC)
      Reversible acute irritations of the skin, eyes, and upper respiratory tract are well-known health hazards associated with direct dermal and inhalation exposure to refractory ceramic fibers, fibrous glass, rock wool, or slag wool in construction and manufacturing workplaces.
      Rockwool’s own Safe Use Instruction Sheet states
      This product may cause temporary mechanical irritation to the eyes and skin. Temporary irritation of the upper respiratory tract (scratchy throat, coughing, congestion) may result from exposure to dusts and fibers in excess of applicable exposure limits. Pre-existing chronic eye, skin and respiratory conditions may temporarily worsen due to exposure to dusts and fibers.
      If you’ve ever worked with Rockwool, you’ll know that it gives off dust and fibers as you install it. The fibers are also friable (break into smaller pieces) much the same as Fiberglass. Neither Fiberglass or Rockwool are likely to kill you, but both can make you itch. Normally in a house the insulation materials are sealed behind drywall or other finishes. In a van, there are more likely to be gaps in the interior surfaces which can let these fibers out over time.

      It’s interesting that Van Haus has tested Rockwool and found that it doesn’t retain moisture. That’s one plus over fiberglass. Rockwool is also much cheaper than Thinsulate, which is a great incentive for many people (including Van Haus) to use it. I’m not sure that the insulating properties per inch thickness are better, but per dollar for sure.

      1. I passed on your comment and links above to Van Haus and they replied that the mechanical irritation is just that: equivalent to rubbing a handful of rocks on your skin, not like fiberglass fibers. They refer to the fibers as breaking up into “rock dust” and being comparable to other sources of natural dust/dirt. They repeated that they are very happy with it in terms of better performing acoustic and heat insulation as well as the varying thicknesses available, fire retardation, lack of moisture retention, ease of working with it, etc. They also say the minor difference in cost doesn’t factor compared with these benefits over other materials.

        Searching on my own on potential harmful effects of rock wool, I see conflicting tests and info on the web and even apparently different definitions of rock wool. (Apparently years ago what was called “rock wool” was partially made up of fiberglass.) Someone gathered and made a nice summary of many reports here:

        Anyway, just wanted to reply so as to leave folks with more info. Cheers!

  12. Oh, I meant to also add that I was planning to use Thinsulate until talking to Van Haus and learning that apparently rockwool performs better than Thinsulate in terms of insulating properties and not retaining moisture, as per their tests. Perhaps you’d like to add a section about rockwool for folks like me who didn’t know about it?

  13. So, sound insulation is one thing and we have the self-adhesive butyl mats installed for that. Thermal insulation is another, but I became concerned with condensation. I think that the proper recipe is to have some self-adhesive thermal insulation (about 1/2″ thick or so) mounted to the inside of the metal walls. This will provide some thermal insulation and drop the temperature of the surface so that condensation is minimized. I see that the popular Reflectix REQUIRES an air gap for effectiveness (which is not easy to achieve) and I see that it does not come with a self-adhesive backing. Strike two. Dodo Thermo Liner Pro seems to be a great solution, but there isn’t anything like that I’ve found in the USA. Any recommendations?

    1. Steven, I think the best approach is to accept that you’ll have condensation inside the metal skin of the van, and deal with it appropriately.

      Other than spraying the entire metal surface and every protrusion with expanding foam, you won’t be able to cover every part of the metal walls. Self-adhesive insulation isn’t going to conform to every groove and corner. In fact it might even put you in a worse position, because it could create hidden areas where water can condense and get trapped so that it hangs around to cause issues.

      For that reason, I’d suggest finding an insulation material that is not affected too much by water, and planning to allow the inevitable condensation to exit the area between the external and internal walls.

      Reflectix may be a useful secondary insulation material, but it’s not sufficient on its own. Like you say it needs an air gap, so a self-adhesive backing would be pointless. We thought we might be able to use this type of material (we chose Low-E rather than Reflectix) to form a water-tight layer on the inside of the van just behind the interior walls to prevent condensation. It didn’t work.

      If I was building a van today, I’d use Thinsulate and no other thermal layers. That way, condensation can come and go as it sees fit without harming the insulation. I may be tempted to add a little more butyl matting for sound damping than the stock van comes with, but I wouldn’t go overboard.

      1. Very wise. I agree. Even if I had my magic self-adhesive Reflectix, the condensation would just form under the metal struts and areas not insulated, as you stated.

        We already have all the Thinsulate and, contrary to conventional wisdom, I think I’ll be applying the black scrim to the sheet metal walls to enhance adhesion and maximize the insulation materials volume in the gap.

        I appreciate your thoughts. Breathing is the key and a nice and warm van will minimize moisture or mold issues; a diesel heater is in the plan.

        Thank you.

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