Ventilation, Heating, and Cooling

Vans are small spaces.  People living, breathing, and cooking in small spaces put out a lot of water vapor, and without adequate ventilation, the inside of the van can become damp and moldy. Additionally, in hot climates its important to be able to move a lot of air through the van to keep it cool.

Vans are a lot harder to keep comfortable than houses.  A van is a big metal box with lots of surface area in which to collect heat from outside and transfer inside, and vice versa. That same big metal box is great at transferring sound as well.  So it’s important to do some level of temperature and sound insulation.

We don’t plan on doing much cold-weather camping. We do plan on traveling in hotter climates, including the Southwest and Central America. Dealing with keeping the van at a comfortable temperature and noise level is a hot topic with a lot of divergent viewpoints.


The most effective approach to ensuring regular and adequate ventilation is to install one or more fans in the roof. If you install only a single fan, then you need to provide air inlets elsewhere in the van, as the fan cannot simply suck air out of a closed box. If you install two vans, one fan can be the intake, and the other fan the outtake.

A good fan pushes the heat and moisture out with a minimum of noise, power consumption, and fiddling.

There are two primary fan vendors: MaxxAir and Fantastic Fan.  The main difference between the two is that the MaxxAir can be left open in the rain due to its larger hood design. Since we live in the Pacific Northwest, having a fan able to be left open 24 x 7 is important.  The MaxxAir can be configured to automatically turn on when the temperature in the van goes above a certain level.

In order to maximize our roof space for Solar panels, we decided to use a single MaxxAir fan mounted as far forward as possible.

To provide intake we have a total of four sliding, screened windows from Motion Windows. The two rear windows are mounted right over the bed, so while we are sleeping with the fan on we will have steady air coming in through these windows right by our heads, passing over our bodies and feet, and exiting out the fan at the front, providing great ventilation in hot climates.

If we need to ventilate the van when it’s unattended (and the windows must be closed), we also have a 4 inch vent located in the D pillar of the van using an existing opening in the Transit steel floor.

Note that the Motion Windows are sliders, which means they cannot be left open in the rain without the installation of some sort of magnetic rain gutter above the window.

Thermal Insulation

Insulation is designed to:

  • Keep the van from heating up as quickly in the summer

  • Keep it cooler if you're running air conditioning

  • Keep the van from cooling down as quickly in the winter

  • Keep it warmer if you are running a heater

For the winter, my experience with the Eurovan has been that the Espar heater was able to keep the cabin warm in temperatures down to 20°. This is without a lot of insulation. And we are not planning to spend a lot of time living in very cold climates. So I'm less worried about dealing with keeping the heat in. A base level of insulation, along with window coverings should be entirely adequate.

We are planning on spending more time in hot climates. But in this situation, there's no way to completely prevent the van from reaching ambient outside air temperature by the end of a hot sunny day. Insulation can slow it down but it won't stop it. If we were spending the whole day inside the van running the air conditioner, insulation would probably help - but who wants to do that! And when the evening finally comes and we are returning to the van for dinner and sleep, insulation is a drawback, keeping the heat in (assuming the outside air temperature has dropped by bedtime). So again, our planned level of insulation should be sufficient.

The one area where there might be some benefit to extensive insulation is if we are running the air conditioner at night. In this situation the air temperature inside might drop below ambient, but the van is still soaking in heat from the outside. However, at night the only area being cooled will be the bed area, which will be insulated to the maximum extent possible along the windows, through the mattress, the overhead cabinets, and the ceiling.

Now as far as solving the problem, this is one of those topics subject to much debate and anguish among DIY van people. People experiment with different materials such as denim, wool, fiberglass, thinsulate, polyiso, and spray foam, different construction techniques including building an entire box with thicker walls, floor, and ceiling within the van.

We want our insulation to:

  • Be non-toxic, and not off gas in our tiny home when the sun heats it up to 120°

  • Not trap moisture. There is a lot of discussion about insulation and moisture. From my research, it’s impossible to prevent the presence of moisture throughout the van, so the key is to avoid constructing the van with moisture barriers that prevent the movement of this moisture out of the van and cavities.

  • Be clean and easy to install, as well as easy to remove later for modifications or repairs

Insulation options

There are numerous blog posts documenting various levels of insulation from none (not recommended) to extreme insulation involving building new walls, ceiling and floor within the van and insulating as you would with a house. I have not seen any data indicating how much more effective these extreme measures are. I do know that my fully insulated upstairs bedroom at home gets hotter than heck on sunny days due to the percentage of windows, so I’m skeptical of extreme efforts given the presence of windows on our van.

If you're interested in some good insulation blog posts:

  • Gnomad Home has one of the most comprehensive analyses of camper van insulation. They used polyiso, which is a great option if you have higher R-value needs.

  • Build a green RV has another nice analysis. They used spray foam, which I wanted to avoid because it's so permanent, gets in the way for doing upgrades and modifications, and is likely overkill for my needs.


We are trying to keep it simple – 3M Thinsulate 600 M from met all of our criteria. We are putting it on the walls and ceiling wherever we can easily place it. We are also making insulated window coverings and some high density foam under the plywood floor. To reduce the transfer of heat through the metal supports that the plywood wall and ceiling panels are screwed to, there are strips of high density foam between the plywood and metal.

Also, there are several draft points in the van that need to be sealed up, notably around the back doors, any exposed holes in sheet metal, and sometimes around the sliding door.

With this approach, I think we’ll get 80% of the potential insulation benefits with a minimal amount of effort.

Keeping the van cool in the sun

Some things I learned:

  1. A white paint job is 30% cooler than any other color, so if you are concerned about keeping your van cool, go with white. Personally I prefer any other color, but I also don’t like sleeping in my own sweat.

  2. Solar panels on the roof will reduce some of the heat gain.

  3. An awning extended out to the side will protect that side of the van from the sun.

  4. Parking in a shady area will help a lot. Some people erect a tarp over the entire van.

  5. Windows are huge sources of heat transfer, and darker tinted windows allow less light in. The best solution is to cover all windows with a completely reflective material like reflectix. Reverse the panels in the winter to trap the heat in.

  6. Keeping a roof fan running all day on hot days will help. 

  7. The stock air-conditioning will only keep the driver’s compartment cool. Consider putting up a curtain or insulated divider if you are frequently driving in a hot climate.

  8. It is extremely difficult to run air-conditioning on anything other than shore power at an RV campground or a generator. Air-conditioning uses a minimum of 40 amp hours of battery juice which will quickly drain even the largest battery banks.

In hot climates you use thermal insulation to reduce the rate at which heat enters the vehicle. However, it is impossible to prevent the vehicle from heating up if you are away from it the whole day and not using air-conditioning, no matter how much insulation you install. So the primary value of insulation in hot climates is to keep the van cool during the morning or if you are using air-conditioning. In the evening it’s your ventilation system that will help get the van cooled down as quickly as possible, and your insulation actually can trap heat instead of releasing it.

Sound Insulation

While we're on the subject of insulation, big empty metal boxes are actually really noisy on the road. Covering the walls, floor, and ceiling with foam backed plywood will help. And so will lining the top corners and left side of of the van with cabinets, and covering the back third of the van with a bench seat and bed.

Thinsulate has the added benefit that it was originally developed as a sound insulator rather than a thermal insulator. So we are killing two birds with one stone by using this product for both thermal and sound insulation.

As with thermal insulation, there are various philosophies and approaches that one can take. I am again following the 80/20 rule, and trying to achieve 80% of the benefit with 20% of the effort. I'm hoping that the Thinsulate and paneling on all the walls will be sufficient.

I do expect to spend an unreasonable amount of time tracking down squeaks, rattles, and knocks as I find those noises annoying in any vehicle. All wood and other fastenings will either be glued and screwed, or buffered from chafing on adjacent surfaces with a thin layer of foam padding. All shelves and drawers will have a foam pad on the bottom. Items in the garage will be strapped down or wedged in. I don't know how successful I'll be given that we'll be driving a 20 foot vehicle filled with household goods, appliances, and cabinetry bouncing down bumpy logging roads.



Keeping the van warm in the winter is a relatively straightforward problem to solve. There are several different heaters that run off of the same fuel as the van – diesel or gasoline. They are very efficient in fuel consumption, small in size with limited space requirements, and relatively easy to install.

We selected the Webasto STC Petrol Heater. It will be installed under the passenger seat, and tap into the Transit auxiliary fuel port. The duct is at the base of the passenger seat which allows us to dry off boots and raincoats by the sliding door.

The other hot contender is one of the Espar models, but they are considerably more expensive, and believe it or not I balked at the additional cost. One other advantage they have is that they run better at higher altitudes, but I'm hoping to lean down the fuel supply to the Webasto is a somewhat hacky work around.


Air Conditioners are power hogs. A typical small, efficient window mount residential air conditioner could run on our fairly large battery bank for about 9 hours before the batteries would be completely drained. And then we would need to spend a few hours running the engine to charge them back up. There are people who have hacked together a residential window mount air-conditioner, either mounting it directly on one of the van walls, ducting the inflow and outflow through the floor, or separating the condenser and the rest of the unit and mounting it under the vehicle. Because of the high amount of vibration, extreme temperature changes, and generally hostile environment of the van, a residential air conditioning unit seemed like a bad idea.

RV air conditioners are not any more efficient (and in fact often less efficient), and because they are mounted on the roof, where we have solar panels, they are not an option either.

CruiseNComfort mini-split air DC air conditioner

I looked into Marine air conditioners (which use of seawater for cooling, so not an option), trucker air-conditioners (which are generally wall-mounted requiring a large hole in the side of the van) and finally found the CruiseNComfort mini split DC air-conditioner. I love everything about it except for the price. Quiet, efficient, durable. Chris, the owner, is great to work with and very knowledgeable about the systems.

The condenser will be mounted underneath the vehicle to the left of the rear differential, the compressor will be mounted under the bed, and the intake and outflow will be ducted into the sleeping area.

With a curtain separating the sleeping area from the rest of the van, I'm hoping to keep the duty cycle down to less than 50%, and it might even be feasible to run this off grid in hot sunny climates. We’ll see…