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Van Build Diary 4.0: Sound and Thermal Insulation – A Joint Discussion

Updated: Mar 15, 2021

As part of the planning process, we knew we’d need thermal AND sound insulation. Little did we know how much these topics could overlap. Little did we also know that there were so many considerations to take into account and how contentious this topic is in the van-build/van-conversion community.

In this post, I’ll cover the options we explored and what we went with - Havelock wool and Kilmat. In Van Build Diary 4.1: Sound Insulation - The Easiest Step in the Build, I’ll lay out how we installed the sound insulation – and how it was a family affair! Thermal Insulation will be woven into several posts as we did it as a multi-step process, bit by bit. Hit the subscribe button at the top of the post if you’d like to be alerted to future posts on the sound installation and all future van-related posts!

* Another quick note: this post contains some affiliate links - I may receive a small commission (at no cost to you) if you purchase through the links provided (Learn more here), which allows me to continue providing these resources!

The Challenges

So, our home is going to be a 24ft. x 6ft. x 6ft. metal box. Immediately, several concerns arise (besides how we’re going to fit everything we need for 5 people to live full-time):

  • Metal is a fast thermal conductor - If the outside world is hot, our little home will get hot fast and if the outside world is cold, the metal frame will conduct out all the heat we’re generating inside. Insulation is an issue in any dwelling and especially so when the dwelling is made from metal.

  • Metal is prone to rust - Our metal home will require sufficient means of addressing the humidity generated by cooking, showering, laundry, and even breathing/sweating of 5 people.

  • - Metal vibrates and clanks a lot – If you’ve ever been in a fully equipped RV, it is painfully loud in the back with everything, including the frame, rattling around. The heavier the cargo is, the less rattling there is but it certainly isn’t eliminated completely. The wheel wells, especially contribute to a lot of vibration and rattles. The walls are also thin and, in the dead of night, you can hear footsteps up two blocks away – not a recipe for healthy, full nights of sleep.

The Available Alternatives

There are sound deadeners and thermal insulators. Interestingly, also, they overlap in their functions, addressing all three issues at the same time – temperature regulation, moisture/rust prevention, and sound deadening -, some better than others. What I mean is that sound deadeners deaden sound and can help address moisture, while some thermal insulators address thermal regulation, moisture/rust prevention, and sound deadening more than others.

Sound deadeners

What a chemical rabbit hole you go down when you start investigating sound deadeners and their composition and if you aren’t a scientist or know everything about different kinds of synthetic rubbers, good luck.

What we were able to glean is that pretty much all sound deadeners for vehicles are made from Butyl – a synthetic rubber otherwise known as Isobutylene-isoprene, which is considered the preferred option for shock and vibration damping and it has excellent resistance to heat and weathering, the two major culprits in a vehicle. It can also withstand temperatures of -40 to 275˚F, unlike other rubber synthetics (e.g. one only went up to 140˚F, which can be desert temperatures in some parts of the world).

To understand how it works, think of a bell. If you just ring the bell, it will vibrate and make a loud noise. If you hold the bell in your hand and try to make it ring, it will sound “dead” – a non-carrying swallowed tap. Well, the sound deadener is like your hand touching every panel and vibratory part of your vehicle so that the reverberating ring of the sound gets trapped.

Now, for sound deadening purposes, you don’t have to cover more than 25-30% of the areas you want to deaden. As a side note, when living in your van, you want to deaden everything – doors, walls, ceilings, floors, and especially the wheel wells.

a picture of the upper inside of the van with kilmat strips laid out on the ceiling, and I am rolling out a strip on one of the wall panels.
That stuff you see under Kilmat? sound deadener, painted over, hardened solid - to be discussed in the next post!

Because of its waterproofing properties, it can help with moisture/rust prevention because the moisture does not come into contact with the metal surface that the sound deadener is adhered to. We first learned about this through Sara and Alex James of Custom Crafted and, given the possibility for water leaks, it seemed a safe, sound, and not too weighty safety net to apply sound deadener to the floor area. In the case of a water leak, the floor will likely be where the water gathers. Waterproofing the metal floor of the van makes sense.

There are a few major manufacturers, all of which have a huge market share, use butyl with an aluminum sheet, and, the ones most favored, come in peel-and-stick sheets. The major difference is whether you want 50mil or 80mil thickness. Obviously, the thicker it is, the more effective it is. This is why most van builders use 80mil thickness. At the same time, sound deadeners add weight to the vehicle, so, keep that in mind when calculating your overall vehicle weight.

One of the go-to sound deadeners in the van community is Kilmat and since it is more moderately priced, comes in peel-and-stick sheets, and gets very good feedback, that’s what we went with.

We will apply it to the roof, walls, and front cab for its sound deadening qualities – covering 25-30% of the area. For the wheel wells and floor, we will use it as both a sound deadener and as waterproofing – covering 100%. For details on how much we needed, the cost, etc., please look out for the installation post. . . subscribe above to get alerts about new posts!

Thermal Insulation

Many options are available in the world of thermal insulation and apparently, it is a highly debated topic in the van life community. Turns out it really depends on which working theory of insulation and waterproofing you adhere to. FarOut Ride has an excellent post on insulation that goes into a lot of the science of heat exchange, types of heat exchange, etc. Interestingly, we came to different conclusions on our insulators, even though I think we agree on the theory!

As a quick side note, thermal insulation is only part of the overall strategy for regulating internal van environments. Other factors to consider are proper air-ventilation, possibly an A/C or swamp cooler, # of windows and insulated window coverings, and even parking location considerations (shade vs. direct sun).

The premise behind thermal insulation is that it creates a medium that prevents heat transfers between the outside world and the inside of your van. The same premise is behind thermal insulation in homes (this is how dense and uneducated I am about this whole topic and how basic I need to break down the information to myself).

These same insulators also address problems of moisture in the interior space. When excess moisture is in the air – after a shower, the breathing and sweating of 5 people, laundry, cooking, humidity outside creeping in –, the competing working theories behind thermal insulation address the challenges as follows:

1) Moisture ought to be completely contained – meaning, the insulation barrier should also be waterproof and therefore, should act as an impermeable moisture barrier. The moisture is contained in the interior of the van and cannot get to the metal. The moisture is then evaporated through proper ventilation systems.

2) There is no way to completely waterproof an area, ever. Even accounting for human error, moisture will inevitably seep into the walls, if not from moisture in the inside air but also in the exterior air. Rather than creating an impermeable layer that then makes it more difficult for the moisture trapped in there to get out, create a semi-permeable layer with a product that is good at taking in the extra moisture before it hits the metal and that releases it back out into the environment at an appropriate time (in dryer conditions).

The insulation you choose will depend on which working theory you subscribe to, as well as what materials you are comfortable with – toxic or non-toxic. Most fall into the toxic category: spray insulation, fiberglass bats, . . . you can usually tell because these are the ones you have to apply with gloves, goggles, and/or a mask on (so the particles don’t enter your bloodstream or irritate your lungs/skin.

There are a few that aren’t necessarily toxic but are firmer, like Styrofoam boards, and therefore, are more difficult to get into all the nooks and crannies to properly insulate everywhere inside the van. Also, Styrofoam is not, as we as know, a sustainable material.

My research into those options stopped here because I only want to use natural, non-toxic materials in our build to the extent possible. We are living in such a small space already, air quality is going to be a priority for us, and we don’t want to think about all that insulation shaking around in there (e.g. fiberglass) and microscopic particles coming loose and leaching into the air for us to breathe. Not to mention the environmental impact. Since there are natural, non-toxic, sustainable options in the realm of thermal insulation, I focused our research on this.

So, there are a few non-toxic ones: denim, hemp, and wool being more common ones. Denim is basically recycled jeans and post-industrial denim and cotton. It is completely non-toxic and is only treated with boric acid for flame retardation, and insect, pest, and mildew resistance. It does require a waterproofing layer as it does not release the moisture well and is easily weighed down. If you are looking for natural non-toxic insulation and subscribe to theory #1, denim could be an option for you.

Hemp was an exciting prospect for us. In our case, we had to reject it early on because 1) the only brands it seemed we’d get our hands on were all out of stock because of COVID-related production and distribution delays. However, for those interested now or in the future, one brand we started looking into is Black Mountain, which produces wool and hemp insulation.

Ultimately, we went with wool, specifically Havelock Wool. We subscribe to theory #2 of thermal insulation, that it is impossible to create a complete moisture barrier and, rather than attempt to and close off routes for moisture to be released back into the air, it is better to use a medium that is good at absorbing extra moisture when necessary and releasing it when appropriate.

Enter wool. The major benefits of wool insulation are:

  • Totally non-toxic – work with it without gloves, goggles, or mask, breathe it, roll in it, whatever you want and it won’t do anything to you

  • It’s “R” value is 3.6-4.3, which is the same or exceeds other natural insulators, as well as, if doubled up to two inches (which is recommended), is the same as many of the synthetic and toxic forms of insulation.

  • It breathes – since moisture inevitably makes it into the walls - theory #2, wool is fantastic at absorbing moisture and releasing it when appropriate. At the same time, the keratin in the wool prevents the spread of mold and mildew. This allows it to outperform some of the other natural insulators, like denim, which cannot address moisture problems.

  • It filters the air and improves the air quality – the wool irreversibly bond with some harmful chemicals like Nitrogen Oxide, Sulfur Dioxide, and formaldehyde to trap it. It is unlike many synthetic materials that actually emit or “off-gas” harmful chemicals.

  • It serves an additional function of a sound insulator – it exceeds other forms of insulation as an acoustic buffer, addressing air-born sound, surface noise, and sound transmission.

  • It is resistant to compression – as the insulating material is compressed, its benefits are reduced. It is the air pockets in the material that are instrumental to its properties. Well, wool is “highly resistant” to compression (at >35 microns).

  • No-Waste – it is compostable and does not add to the landfill

Well, that about does it for me. There isn’t much else I need to hear. Again, we did a cursory look into hemp insulation but that option was not available to us at the time we needed due to COVID-related production and distribution problems. We would have looked into it a bit more had it been available. I’m not sure which I’d go with if it was available. Maybe we’ll give it a shot on our next build if there is one?

So, for our current build, we’ve decided the following for our Havelock Wool Insulation: only 1 inch to the floor to give ourselves one more inch of height (we’re adding radiant heating in the walkway anyway for the really cold times), 2 inches on all the walls and ceiling where most of the insulation is required.

We’ve ordered the bats because they are easy to cut and fit directly into the metal frame. Because it is so flexible, it can easily be cut into strips and shoved into the ribs and all the nooks and crannies as well.

One very important note: We will install our electric system before installing the insulation into the walls and ceiling. The insulation provides an extra layer of protection against accidentally screwing into an electric wire and creating a “live wire” situation in the van.

For now, we are installing the insulation into the floor and the front cab areas so we can close the subfloor and put the front cab panel back into place. We were waiting for our wool to arrive before installing the sound deadener there too because the feedback from other van-builders is that it is a pain. So, we wanted to uninstall and reinstall only once for sound deadener and insulation.)


So, to summarize, sound deadeners can deaden sound and waterproof the metal where they are attached to the metal, address issues of sound transfer and moisture control, which is why we are applying 25-30% to the walls and ceiling and 100% to the floor. A thermal insulator like Havelock wool creates a non-toxic way to address thermal AND sound insulation (at which it performs better than many others) AND addresses moisture control as well (something other natural insulators are less capable of).

I hope this information helps those of you trying to figure it all out. There is a lot of information out there. Deciding what theory you subscribe to, as well as what type of material you are comfortable with, are the most important decisions in figuring out what insulation material(s) to go with.

I’d love to hear, in the comments, what insulation you would go with (even if just in an imaginary build – although one day it will be real!). Please share this post on your social media pages, as well as just pass along to friends, and thanks for supporting On An Imperfect Journey!


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