RV Roof Vent Fan Install

One of the first modifications to our RAM Promaster van was to install a roof vent fan. These are quite common in RVs to provide ventilation and fresh air. We wanted to cut the hole in the roof to install the vent while we still had an empty shell since cutting overhead creates a lot of small metal particles. We will walk you through our RV roof vent fan install in this article.

First, we needed to determine the location. Our floor plan will include a fixed bed at the rear of the van, so we wanted the vent over the bed in order to provide ample air flow while sleeping. I also knew that we intended to add solar panels to the roof as well as an air conditioner up on top at some point. In addition, we needed to leave room for a black tank vent pipe and an entry location for the solar panel cables. It seemed that we needed to turn to CAD (cardboard aided design) for our roof layout.

Ram Promaster DIY RV roof layout with solar panels, vent fan, and air conditioner.
Cardboard panels of the exact size of our roof objects (solar panels, vent fan, and air conditioner) are arranged for optimum layout.

Once I confirmed that the roof layout would be possible, I did realize that the vent fan would need to be as far back as possible to leave room for the other items and to prevent solar panel shading. This also would complement our plan to have operable windows towards the front of the van, since it would pull fresh air back through the full length of the RV. We looked an many models, but ultimately decided to purchase and install the Maxx Air Deluxe Fan with Remote for our location.

I constructed a wooden frame from pine and screws that would be mounted inside against the van roof. The thickness was calculated to match the finished level of the ceiling. This frame was placed at the desired location inside the van and two small holes were drilled at each inside corner of the frame. These alignment holes would allow the frame to be placed on top of the roof and lines drawn for the cutout location.

Masking tape and paper were placed around the cut location to prevent scratching the paint finish and to protect from the metal shavings. A handheld jig saw was used with a new metal blade (Bosch T118A) to make the cut. A few metal screws were installed to hold the wooden frame against the inside roof. The voids between the frame and metal roof were filled with window and door expanding foam.

RV roof vent fan opening with a wooden frame and expanding foam.
The roof opening with the wooden frame visible in white. The yellow expanding foam was trimmed after it cured.

Once the foam cured, it was trimmed flush and the plastic mounting flange was placed into the hole to mark the location of the numerous mounting screws. These screw locations were pre-drilled with a small pilot hole and all of the area was cleaned up with denatured alcohol to remove any dirt or other residue on the paint. Butyl tape was applied to the bottom side of the mounting flange, and multiple layers of butyl tape were applied to the depressions in the roof to bring them up to level. The flange was then pressed onto the roof surface and all mounting screws were installed and tightened.

RV roof vent mounting flange and butyl tape photo.
The roof vent flange is mounted, and the butyl tape can be seen under the white plastic flange against the metal roof.

In order to fully seal the installation against weather, a Dicor self-leveling lap sealant was applied to all screw heads, the exposed butyl sealant and edges of the mounting flange. The only remaining task was to attach the fan assembly with four screws into the mounting flange. This fan design prevents rain from entering the vehicle while the vent is open or operating. This will be a welcome feature during wet weather days.

Finished look of the Maxx Air Deluxe RV roof vent fan. The self-leveling lap sealant is difficult to apply with a perfectly straight line, but the roof is high enough it cannot be seen from the ground.

We hope this information is helpful if you plan to install a roof vent in your DIY RV van. A list of the items that we used for this install is below.

We also have produced a Youtube video detailing the RV roof vent fan install that provides a bit more detail. Click the image below to view the video.

RV roof vent fan install video for a Ram Promaster DIY RV van.

Happy Trails…

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