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Van Build Diary 5.1: Ventilation is a MUST

Updated: Feb 16, 2021

When: One of the first to-do’s in the van build, before the Roof Liner

Why: Air Quality, Moisture & Temperature Control

Who: Marino

What: Two MaxxFan 5200 Fans

Where: Mid-Front and Mid-Back

How: Step by Step Installation

Air ventilation is an insanely important aspect of any van build. Without it, the air remains stagnant and retains moisture and smells. I don’t think anyone needs clarification on why stagnant and odorous air is undesirable. As for moisture, it impacts how our bodies feel at different temperatures and it is the bane of any van dweller’s existence because it leads to rust and destruction of your whole home!

So, we knew we needed to have good air circulation in the van, at all times of day, to address all the above issues. If you’re interested in exploring our thought process around the whole topic, please enjoy!

Marino sitting on the roof of the van pointing to the rear fan he just installed.
The install was all Marino - look at him and his handy work!

This is one post in a 5-part series on everything that needs to go up on the roof:

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The “When” of Ventilation

The “when” is the easiest to get out of the way: Do this and everything else on the roof first!

Any ventilation system that relies on more than opening a pre-installed window requires cutting a hole into the van. Cutting holes exposes untreated metal to the air and creates a potential for rust. The exposed metal is in two forms: 1) the remaining part of the roof or wall that was cut into, and 2) the tiny bits of metal shavings that came off during the cutting. All shavings have to be removed or they will rust and can cause other metal they are in contact with to rust as well. It is easier to remove these shavings when you’re dealing with an empty canvas, so it is better to install anything that requires cutting into the walls first.

Also, any cut into the body of the van requires a proper seal to keep water out. Most seals require sitting flush to seal properly.

Now, most ventilation systems are installed into the roof. The roof is much more prone to damage and rust than other exterior parts of the van. Frequently, roof liners are put on, as we will be doing and discussing in 5.4 of this series, as an added protection. So, if you want to get your roof protected, you have to make all the cuts into the roof before applying the bed liner.

And, you want to do the bedliner before you start installing a roof rack or solar or a roof deck or whatever else you’d like up there. So, if you don’t want to get too far behind in the rest of your build, do this and other roof installs first and all other roof work, as well as completing your solar system, can follow smoothly.

The “Why” of Ventilation

As previously mentioned, and we all probably know, air needs to circulate to prevent stale air and support moisture and temperature control.

Temperature: We have all experienced the benefits of a fan on a hot summer day (even without air-conditioning). Just feeling the air moving over your skin creates a temperature differential that helps you feel cooler. My brain is taking me back to last year of college, New York summer, no A/C, top floor apartment - fans, cold showers, wet sheets - the only way we survived!

a room fan to the left, a blurred body in front of it to the right

Moisture: This is usually an obvious one – showers, cooking, and washing dishes. Even just breathing and sweating can generate moisture in the air. Being in humid areas also can generate moisture in the air as the internal environment balances with the external environment – rainy days, tropical climates, and winter turning to spring. Moisture poses the greatest risk to your van/home because of condensation, which leads to rust!

A fan helps to keep the air moving. So, the moist air from inside the van is moved out as new, dryer air is moved in. If it is humid outside, then getting the air moving can create an evaporative effect too.

a glass window covered in condensed air and water drip lines running down it with a blurred outline of a person behind it
Condensation will be your worst enemy!

Air quality: The simple act of breathing impacts the air quality in the van – as we breathe carbon dioxide out and oxygen in, we change the quality of the air. Having a way to pump fresh oxygen-rich air in is important. So, moving air can remove air pollutants and . . .

Add to breathing, all the smells generated by 5 people living in a van: body odor, mouth odor, the smells of cooked food and food waste for 5, shoe odor, dirty clothing odor, and everything that we bring into and out of the van. . . there is a lot going on inside that space. Keeping the air flowing helps with the odor control and air quality in the van.

So, we need a way to move air in the van. The question now is . . .

The “What” of Ventilation

So, a quick side note is that A/C does not change out the air in a van. A/C units are usually self-contained and simple circulate the air already inside. They do not necessarily change out the air inside.

The Free and Nearly Free Options

Now, there are many ways to ventilate your van. The most obvious and free one is to crank open some windows! Simple enough. However, to really address all the above-mentioned issues adequately, opening some windows alone isn’t enough and isn’t always desirable.

The first issue, for me, with just using windows is security. Whether we all leave the van but want the air to keep circulating, whether boondocking in a Walmart parking lot, whether spending the night in a remote area of a national park where bears run free. . . those are all good enough reasons for me to want to keep the windows closed frequently enough that I need to have another option to vent the van.

Another issue is rainy/snowy/hail days. You can get a wind deflector (minimally effective) or a t-vented window. You still have addressed the security concerns though.

So, the RV world has some cheaper options for that: Gable vents or wind-driven vents. Gable vents are usually located in the side of the van, have a few slits and ensure that there is airflow between the outside and inside environment. However, they do not actually move the air and rely on something else pulling the air into or out of the van. Same thing with wind-driven vents. Once something gets the air flowing over the vent, the vent will allow air in or out, depending on where the air is being pushed/pulled from.

the side of an RV showing a fridge vent ont he lower left and a passive vent installed above the stove and kitchen bunk window
The one above the window is right above to the stove.

These vents address the security issue because you can close up your windows and still have an air exchange with the outside environment. They also address air flow concerns on rainy and snowy days.

However, what happens those days when there’s little to no wind? All of these options rely on natural air flow, which on still days, will not provide sufficient ventilation to avoid condensation, which ultimately leads to the destruction of the van!

So, you need something stronger and that something stronger is an electric roof vent!

The Only Realistic Option: Electric Roof Vents

Now, there will be a whole series on the van’s electrical system soon – we are still building out the system (what a learning curve!). Suffice it to say that you NEED a 12v electric roof vent in your van. These fans keep air circulating in any weather, don’t post a security risk, and can keep the flow even on days with little or no wind.

There are three major brands out there that all my research kept leading me back to: Aircel’s MaxxFan, Dometic’s Fan-tastic line, and Fiamma. Ultimately, we went with the MaxxFan 5100K (the 6200K is the same model in black):

I really think it’s the obvious winner:

  • It has 10 speed options

Fiamma only has five and Fan-tastic only has three.

While Fiamma’s highest setting draws less amps than MaxxFan’s highest setting, Fiamma’s highest is at MaxxFan’s 8. This means that with MaxxFan, if I’m worried about amps, I can keep the highest speed at an 8 (or lower even). However, say, right after the shower or after cooking a hearty soup, MaxxFan gives us the option (if we so choose) to vent at two higher settings and we don’t have that option with Fiamma. I always think it’s better to have options.

Along the same lines, having 10 different settings allows for more nuanced variance in vent speed, rather than the cruder gradations when only 5 settings. This is important not only for more variation in air flow but also, the ability to control amp usage with more specificity.

While there is ONE Fan-tastic Fan model that has 13 speed options (all the rest only have 3 options), it is the remote-controlled option (I’m fine with a control panel on the ceiling unit), which makes it more expensive, AND you still need to separately purchase and install a rain cover, making it even more expensive. As for the 3-speed fans, the same answer holds as for Fiamma. For example, at a 3-speed Fan-tastic Fan’s lowest speed, it is still drawing 1 amp and you do not have the option to go lower, whereas with MaxxFan, you can choose to set it as low as a .23 amp draw at its lowest setting.

  • It comes with a built-in rain cover

Most brands, including Fan-tastic and Fiamma, have a rain cover that you can optionally purchase and install over your vent.

I don’t know why anyone would do this if they already come preinstalled.

Of course, if the fan without the preinstalled rain cover were significantly superior in quality and performance, I understand.

However, here, when looking at Fan-tastic’s ONLY more-than-3-setting fan (and therefore, only comparable-in-performance fan), it is already more expensive, it already requires spending even more on the rain cover, and the rain cover needs to be additionally installed? No thank you.

Why would I go with anything else?

A cursory search of the 13-speed Fan-tastic Fan model shows that you can’t get it for less that $300 AND the rain cover is a minimum of $45. That’s $345 for a fan!

As for Fiamma, it doesn’t have a rain cover so, that option is out.

Our MaxxFan fans – yes, fans with an “s” (meaning, plural), cost us $263.36 each and came with the rain cover already installed!

The “Where” of Ventilation – Placement

the roof of the Sprinter showing the placement of one vent in front and one in back
Roof shot of the placement of our fans - see, they were the first to go up on the roof!

Part of our “where” question was “how many”? I really need to thank Curt and Snow of for all of their thoughts on the issues of temperature control more generally, and the importance of different strategies for temperature, moisture and air quality control. They’ve got a fantastic (no pun intended) youtube video that goes into detailed considerations of planning your ventilation system.

The idea behind two vents came from them (I’m sure others have thought it and said it but they were the first ones to introduce us to these considerations) and it goes a little like this:

If you only have one vent creating an air exchange, then air can either only enter or exit the van and not both. So, if you’re trying to move stale air out, you’re sucking air out but you don’t have another entryway to bring new air in, . . . you’re creating a vacuum. If you’re trying to move new air in but you don’t have another entryway to take the old air out, . . . you are building the air pressure in the space.

So, you need two places for air to enter and exit your van/home: one to bring air in and one to take air out. This means two vents. Now, depending on your budget, you could install one passive vent and another motorized vent. It would keep costs low. However, that could put a lot of strain on the one vent fan to circulate all the air and bring air in through the passive vent.

When you have two properly spaced, you can create easy-flowing air through the whole van.

So, now that I’ve made my case for two, the question becomes where to place them.

It is recommended that you place one as close to your cooking/showering/high moisture activities so you can whisk that air out of the van before the moisture has a moment to settle. That means, one needs to get placed relatively close to the middle/front for our layout.

Now, that covers the shower, kitchen and my mom in our build. However, we have not guaranteed any good air flow in the back where Dante, Leila, Marino and I will be sleeping. I’d say it is pretty important to generate good airflow where four people are sleeping all together.

So, that means one in the middle/front of the cargo area and one in the back by us.

Where exactly?

1) Anywhere where you are NOT cutting into the ribs or joints on the roof. The biggest “no no” is cutting into this joint on your roof. Another big “no no” cutting along the cross ribs that you could/should be using to run wires through/near/along and that you will attach your ceiling to/mark the highest your ceilings can be (in theory, the ceiling could be higher but you’d have to find a way to work the ribs into the aesthetic AND you’ll lose insulation inches.

one photo of the exterior roof and one photo of the interior roof with arrows pointing to the seams and ribs in the van and text saying to never, ever, ever cut into these
. . . EVER!!!!!

2) We have a non-ducted A/C that we need to install so that some vents can blow back to us and some can blow forward to my mom. This means that the very middle of the roof/ceiling needs to be dedicated to the space the A/C needs (for the cut, and for the overhang on the roof-side). So, no fans can get too close to that.

You'll see in the photo below that our ideal placement for the fan was too close to where we needed to install the A/C.

3) The space you are installing needs to permit a 14” x 14” hole to be cut into that part of the roof.

You'll see in the photo below that the next best placement of the vent is in an area of the roof that is too small between the ribs to have the fan go there.

4) Make sure you’re leaving enough room on the ceiling between installed pieces to also have lighting interspersed. We need to have a few lights all along the ceiling so we need space between the rooftop applicances.

So, all of that translates into the following placement of our fans:

front half of the ceiling with the black bottom of A/C farthest to the left, and fan farthest to the right
Ideal placement? Right next to the A/C (big black square thing), but too close and next area over was too small
back half of the ceiling of the van. Fan installed right over bed area.
Perfect placement over the two beds!

The “Who” and the “How” of Installing Ventilation

Well, it turns out it is not in my cards to do any work on our roof. The kids need me too frequently to give me enough time so I don’t have to climb up and down 10 times during the install. I hope my fate will be different when it comes to installing the windows.

So, the “who” is Marino:

Marino on the roof pointing to the rear fan he just installed. The photo is a repeat from earlier.
Marino on the roof redux!

The “how” is as follows:

Before I begin, Mathers on the Map has a great video of his MaxxFan Fan install. A few notes as far as our build goes in comparison to his:

1) He reinforced the plastic frame of the MaxxFan Fan with metal. It makes absolute sense (you’ll see it in the install) as plastic will obviously go through significantly more wear and last less than metal. However, for the quantity of installs we’ve reviewed and seen, the benefits did not seem worth the added time, especially since we are new to cutting holes in metal and all.

2) We borrowed from him the installation of an adaptor on our rear vent. We haven’t seen many people do it but the adaptor is great because the plastic frame doesn’t sit flush against the metal if you are trying to install where there are vertical ribs on the van. Our front fan sat flush with no ribs jetting out where we wanted to install it. We only did it on the rear fan. The adaptor gives you a lot more flexibility in terms of positioning the van in places where there are vertical ribs. DIYVans, the company that sources these adaptors is run by very friendly folk who can tell you exactly which adaptor you need if you send them a picture of where you plan to install it (still, don't cut horizontal ribs or the seam!).

3) Mathers did not install the interior wood frame for the vents at the same time as installing the exterior portion. We did because it was easier to clamp the interior wood frame down before the fan was installed above it. I’m not sure their reasons for not doing, I’m just clarifying a difference here.

We are not yet youtubers and are still figuring that whole platform out. So, in the rest of the post, I will provide a how-to for the install, with pictures. However, if you’d rather see a video, by all means, check out Mathers on the Map for a clear, organization demo of the install.


Step-by-Step Installation of the MaxxFan Fan

Here are the items you will need for the install:

  • A hammer and a nail or pointy screw (how do you like that terminology – pointy screw!)

  • A plastic bag to tape on the underside of the cut so that the metal shavings fall into the bag and not all over your van floor

  • A jigsaw with metal-cutting blades (Bosch T118A) - I used my dad's (not even sure the brand) but they are very affordable. Amazon has a Black and Decker one for less than $35 - a great deal, especially if you have a lot of cuts to make (we have 5 windows, 2 fans, and an A/C, and probably a fridge vent too).

  • Painter’s tape to tape out the cuts AND to cover the jigsaw so it doesn’t scratch your roof as you cut AND to tape up your plastic bag

  • A ruler

  • Some kind of a marker to mark where to cut – whiteboard markers are great because the ink comes off easily when not needed.

  • An electric drill to cut holes into the metal

  • A metal file to file down the cut area and remove any metal fragments

  • A broom or hand vacuum

  • Rustoleum or another rust-prevention paint to cover the cut edges