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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.


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

  • 3M Marine Adhesive Sealant Fast Cure 4200 - the link is to the one we used. It requires a caulking gun so make sure you get that too!

  • Butyl tape to seal the plastic vent frame to the roof

  • 4 clamps

  • The MaxxFan fan and all included components

  • A screwdriver

  • Self-leveling lap sealant and a caulking gun – one tube per vent

  • 2” x 2” wood to frame out the inside of the vent area

  • 4 corner brackets and accompanying screws

  • ONLY IF USING AN ADAPTOR, the adaptor and a kitchen sponge (rough side))

  • Optional: a wide, thick pillow or plywood to stand/kneel on so your weight more evenly distributes on the roof and isn’t pressing down on one area in particular (don’t forget that when you’re cutting into the roof, you are impacting its structural integrity with each additional cut)

Prepping the Area

Words of caution: prep well or you will end up having to interrupt the install because you forgot to bring something up on the roof that you need. Get everything up there you’ll need right away and you won’t have to turn it into a Stairmaster challenge.

First, you’ll want to make a mark in the center of your 14” x 14” hole. Alternatively, as some people do for their windows, they can make marks all along the lines they will cut with the jigsaw. The easiest suggestion, though, is to mark the center point with a marker and give that spot a nice hard hit with the hammer and nail or pointy screw (yes, there it is again). This should create an indent on the exterior of the roof (don’t be afraid to hit hard, you’re cutting that part out anyway), marking your cut from the outside.

Side note: You might think you can just go on the roof and measure from the center of the circle. We measured on the inside to make sure we had a full 7" in each direction and wouldn't cut a rib when installing from the center. If you're not cutting into the center of a clear marker like this circle, then it is best to measure from the inside and mark the center of your cut from the inside.

showing the mark from the outside marking the center of our cut
See the tiny raised indent in the circle?

Next, tape a trash bag to the ceiling area to catch as much of the metal shavings as possible – we’re avoiding rust, people!

a trash bag taped to the inside of where Marino will cut the fan
You might want to double-bag it. They can rip easily from the metal shavings

Now you’re ready to head to the roof. For this first part, you’ll need 1) the taped up jigsaw, 2) the electric drill, 3) the marker, 4) a ruler, 5) the metal file, 6) the rustoleum and an applicator, and 7) the heavy duty pillow or plywood.

Once you’ve found the indent, you’ve found the center of your cut. You should be measuring 7 inches in every direction to figure out the lines you’ll need to cut for your 14” x 14” hole. Line up the plastic frame with those marks and, using the marker, trace the inside to give yourself a guide while cutting.

Make sure to get that pen as close to right under the frame as possible. We don’t want the cut inside the frame as the frame needs to be just slightly smaller than the hole to fit inside of it. Also, you will want to tape around where you're cutting as an added safety so the jigsaw doesn't scratch the roof.

Making the Cut

Drill just inside of the four corners of the marked hole so that the outer-most part of the holes line up with the cuts you will be making. This is actually an optional step if you’re really good with a jigsaw and feel comfortable cutting around curved corners. We weren’t comfortable with that.

the taped out area to be cut for the vent opening, with 4 holes drilled into the corners
And connect the dots!

So, the four holes you made with the drill allow you to cut a straight line from one hole to the next, just connecting the dots. . . And now you cut! If you’re really worried about making the first cut. Drill a hole into the center of the marked area and try your first cut from the center in any direction just to feel what it is like to cut into the metal. Then. . . you cut!

Once you’ve cut a couple of the sides, tape them up to keep the piece from bending inwards as you cut the other side of the opening.

the vent opening with the cut metal square hanging from where it was taped and showing a hole in the plastic bag meant to keep metal shavings out of the van interior
See the shavings? And the bag ripped - hence, suggesting double bagging

Protecting the Area from Rust

File down the entire area you’ve cut, making sure to smooth the edge as much as possible and remove as many shavings as possible from that area. Also, sweep or vacuum the area to make sure you remove metal shavings from all areas of the roof where you will be working.

Paint the Rustoleum on the exposed metal and let it dry for 2-4 hours. You can just use one of those wood foam applicators (your kids have probably used them to paint with and make sponge blobs). You can go ahead and remove the plastic bag, as well as any additional shavings that might but shouldn’t have gotten through.

Making and Attaching the Internal Wooden Frame

While the Rustoleum is drying, you can prepare the internal wooden frame. Cut your 2”x2” into two 14” pieces and two 10” pieces. If you’re all fancy, you can make four 14” pieces and cut the corners into 45-degree angles to connect the four pieces that way. You can reinforce your connections with wood glue but simply screwing the corner brackets in should be enough to hold it together.

Now you have a square frame that will glue onto the inside of the cut. Apply your 3M Marine Adhesive Sealant and fix the frame to the inside of the cutout. Put the clamps in place and allow it to dry for 50-90 minutes.

Installing the Adaptor (If You Need)

Again, make sure you have everything you need with you before you go up again: the adaptor, the 3M Marine Adhesive Sealant, the kitchen sponge, the clamps and the plastic frame for the fan (to make sure you attach the adaptor properly).

As mentioned, we only needed an adaptor for the back vent and not the front vent. For the front vent install, we skipped this step. Also, Marino only documented the install of the front vent. So, again, I’m referring you to the Mathers install video for this step. You can find it at 14:00 minutes if you want to skip to that part of the video.

To briefly describe the steps here, scuff up the area the adaptor will adhere to with a regular kitchen sink sponge (the rough side). Apply the 3M Marine Adhesive Sealant to the underside of the adaptor. Lay the adaptor down – you can fit the plastic frame inside of the adaptor to make sure you are gluing it down exactly where it needs so the frame can slide into it properly. Clamp it down and let it dry for another 50-90 minutes.

Attaching the Plastic Frame

You’ll prep the plastic frame with the butyl tape before going back on the roof. You can already do this part while the adaptor is drying. Or if you don’t need the adaptor, then while the wooden frame is drying.

You will line the bottom side of the plastic frame with the butyl tape. Identify the back side of the fan. The metal clips are on the side, so just decide which side will be the back and apply the butyl tape so that the seam that will be created meets at the back. You want the seam in back because, as you drive forward, water will run from front to back and you don’t want it hammering away at that seam.

the underside of the plastic frame for the fan with black butyl tape applied so that the seam is NOT on the sides and will be placed in back
You can see the butyl seam at the top. This will be the back of the install.

Time to get on the roof again. Make sure you have the clamps, the drill with a 1/8” drill bit, the screws that come with the fan, the plastic frame (with the butyl tape already attached, the self-leveling lap sealant and the fan, itself.

Press the plastic frame into the adaptor (or roof if no adaptor). Make sure the seam is in the back! You can use a couple clamps to keep everything pressed down and in place while drilling the holes into the roof. Drill holes into the roof (or roof and adaptor) where the holes are on the plastic frame. Then put the screws in place and tighten with the screwdriver.

Next, you can place the fan itself onto the plastic frame and screw it in with the four screws provided.

the fan screwed into the plastic frame screwed into the roof with the 13 screws provided
You can see the screws for the plastic frame and then 4 screws attach the fan to the frame

Now you’re ready for the self-leveling sealant. You’ll want to use the whole tube. Make sure that you apply it to cover every seam and screw opening so that everything is completely sealed.

the fan installed on the roof with the lap sealant around the edges covering all the screws and seals
It's messy - there's nothing much you can do about how messy it is. It just is.

Testing for Leaks

The lap sealant takes approximately 4 hours to become waterproof. It takes 48 hours to be 80% cured and can take up to a full month to completely cure. 48 hours should be enough to test the seals.

It can be scary AND, if it is sealed, is a total confidence booster! Just grab a hose, and get water flowing over the roof to make sure that water is hitting the seal on all 4 sides.

And that’s about it on the install!

While the A/C install is very similar, the next post in this series will cover all the considerations involved in deciding on A/C, which A/C, and the install. If you’d like to be alerted to future posts, just hit the subscribe button at the top of this post!


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