Mod: RV Floor Vent

Floor Vent Installation

Ventilation in a Recreational Vehicle is of utmost importance in a constant fight against humidity and condensation. It is even a bigger issue while boondocking, and where air-conditioners don’t work.

The basic options you have is opening your windows and the use of a roof vent, to increase airflow throughout your RV. That has become more difficult for van owners, as the windows of many of the new European vans are fixed and don’t allow ventilation.
We strive to enhance natural convection in the RV, where airflow is induced by temperature and height difference and distance between air entry and exit points. Introduction of a floor vent in combination of a roof vent, could enhance the airflow substantially, even without mechanical means.
The vent would be situated at the opposite end of the vehicle, at a maximum distance from the roof vent, close to or in the floor, preferably in the center of the RV, where outside summertime temperatures are coolest.
Leaving both vents open, even while you’re away, could bring the excessive heat during summer, down close to the ambient temperatures outside the vehicle.

In this project, I’ll show you my solution in my 2016 Ford Transit. With some modifications, the idea should work for other vans like the ProMaster or Sprinter as well or in any other RV. I’ll be cutting into my vehicle, which may have consequences for the van’s warranty or even worse. Make sure, that you know what you’re doing or consult an expert!

What You’ll Learn:

  • Where to locate the floor vent.
  • What materials to use.

What You’ll Use:

  • Wheel Chock
  • Drill.
  • Narrow Drill Bit.
  • Wide Drill Bit.
  • Hole Saw.
  • Hacksaw or Oscillating Multi-Tool.
  • Metal File.
  • J-Roller.
  • Pair of Pliers.
  • Pair of Scissors.
  • Sandpaper.
  • Tape Measure.
  • Painter’s Tape.
  • Marker.

What You’ll Need:

  • 4” Flexible Foil Dryer Duct.
  • 2 Aluminum Flashing.
  • Gutter Screen (min. 4” x 5.5”).
  • 2 Bolts, Washers and Nuts.
  • Paint.

Approximate Duration For This Project: 3 hr.


To induce natural convection, the location of a floor vent should be at the greatest distance from the roof vent. In my Ford Transit LWB, I choose the rear center of the roof as the place to install the roof vent; the location after the last cross member offers just enough room to fit a standard vent. This automatically forces me to locate the floor vent towards the front of the vehicle. Sometimes roof ventilation is in the front of the RV; a floor vent should then be placed towards the rear. Avoid any chance of toxic fumes from entering the vehicle; p.e. a location near the vehicle’s exhaust pipe is not safe.

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Besides in the front center (where a vent would interfere with foot traffic between the cabin and the living area), I have three good options for installation. The entire length of the step-in area, immediately behind the passenger seat: this offers easy access to the area underneath the vehicle, but is in full view when you enter, exposed to dirt and it may interfere later on with the placement of water tanks under the van.
Close to it, is a small area at the very left, under the floor overhang that lends itself to it, but being closer to the rear vent may negatively influence the convection flow.

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Ultimately, I choose a location behind the B-pillar, inside the wall cavity. This wall will be covered with a Murphy bed with an opening where the air can enter the living area. Within the wall, a 10-15 square inch (50-100 square centimeters) area of the floor will be removed, to give access to an existing ‘porthole’.

With some effort, an ordinary 4 inch (10 cm) dryer duct will fit the cavity and the bottom opening and be covered with a ‘bug/rodent’ screen.

The duct seems fragile, but actually is quite sturdy and will be connected to the screen with a connector, made out of two pieces of aluminum flashing. One will fit over the duct, the other inside and they will hold the duct in place. The screen is made out of a piece of gutter screen, sized to fit the opening. The wall cavity will be filled with insulation at a later time.

The other end of the duct will be installed during the installation of the bed, with a manual ‘blast gate’ that can stop the airflow. At that time, a decision will be made if a small fan should be included in the setup.

Step-by-Step Installation

Gather all the tools and materials before proceeding. Regularly fit the materials, to avoid costly mistakes. Always use wheel chocks and secure your vehicle, when working under the van.

  • Take measurements at all locations and be sure that all components will fit.
  • Verify if you can access the wall cavity. Every make AND model has different specifications.
  • Inside the wall, locate the opening and drill a pilot hole for the hole saw as far forward as possible.
  • Follow up with a hole saw. I use one with 1-1/4 inch diameter.
  • Verify the location of the hole from the top and from the bottom.
  • Make an oval template of the duct, that still fits the depth of the wall cavity.
  • Place the template in the wall, starting at the beginning of the hole and backwards.
  • Drill another hole at the other end and as many as possible in between to remove most of the waste.
  • The wall is narrow and I used a hacksaw blade to remove the remainder. If you can fit it in there, an oscillating multi-tool may be easier.
  • A metal file smooths all the edges.
  • Use some coarse sandpaper the remove the brim underneath.
  • Paint the exposed metal to protect against rust.
  • The depth to the exit screen is about 8 inches. Mark the extended duct at 12 inches.
  • Flatten the end of the duct to about 3-1/2 inch. The depth of the wall cavity.
  • Insert the duct up to the mark.
  • Flatten the two pieces of aluminum flashing.
  • Measure the size of the entry hole.
  • Mark each aluminum sheet and cut to size.
  • Mark the diameter of the duct onto the aluminum pieces.
  • Mark an inner oval at about a 1/4 inch distance.
  • Drill a wide hole in the center of both pieces.
  • Cut along the inner line of one piece.
  • Cut ‘tabs’ to the inner line on the other.
  • Shorten the tabs.
  • Cut the wire in the duct at 360 degrees, forming one circle.
  • The first piece fits around the duct, the second fits inside, with the tabs folded in.
  • Create extra hooks on the tabs, by bending the end of the tabs inward.
  • Cut the screen to size.
  • Pre-fit the screen.
  • Mark the screen, where the bolts are inserted.
  • Copy those holes to both aluminum pieces. Be aware, they fit only one way.
  • Drill the holes in the aluminum.
  • From underneath the vehicle, pull out the duct.
  • Fold the excess duct foil inwards.
  • Slide the first aluminum piece over the metal ring at the end of the duct.
  • Then add the one with the tabs.
  • Add the screen and bolt everything to the frame.
  • Store the other end of the duct inside the wall until you’re ready to install.

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Only a few cheap materials are needed and most of you can do this work. Cutting into the frame of a (new) vehicle may or should not be so appealing to some. Only proceed if you know what you’re doing.

The duct, flashing and gutter screen used during this part of the project, were acquired locally and the total cost was about $14.45.

Other projects of this Van Conversion:

Download This Guidefloor-vent
pdf [ .pdf Download ] – Size: 1.3 Mb

I’m just a DIY’er with a lot of common sense, but with some of the projects, I use some tools and materials, that require you to really know, what you’re doing. Always read the manual and consult an expert if you’re in doubt.

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  1. Great idea and an excellent job! (Good slideshow too). I will be doing this to my Roadtrek very soon, but with one change. Here in Florida the roaches could fit thru that size screen so on the inlet I will be using a piece of aluminum window screen.

    1. Thank You!

      I’m working on a Murphy bed now, where the other end of the floor vent will enter the interior of the van. At that point I’ll probably install a ‘blast gate’ (as used in Woodworking Dust Collection). This opens and closes the vent as necessary.

      I’m located in Central Florida, with the same issues as you have and planned the incorporate on the interior side, a fine screen to repel the no-seeums. This should be readily accessible for cleaning.

      Whenever you finish your project in your Roadtrek, I would appreciate a few pics to see how it looks like.

      Van Williams

  2. Awesome progress. I want a Transit also but I am sceptical of my ability to do so many mods to the vehicle.

    1. Thanks!

      You make a good point. Converting a cargo van is, or can be a manageable project, certainly when you have reasonable expectations. I try to show that by divvying up large and sometimes complex modifications into simple, one-or two-day projects that most of us can do.

      That may hide the fact that when you start a conversion, you sign up for a complete conversion, not one you abandon after a couple of weeks or months. And it is a longer term commitment.

      My approach is to have a complete plan for the conversion, yet stretch it out over a longer period. Start with the primaries, like a bed, porto-potti and 12V supply (for phone, tablet, computer); this way you can start making short overnight trips almost right away. Then with every additional amenity, you create more comfort in the van and you can expand your destinations further apart.

      It comes down to how much experience you have as camper and as DIY’er and how much confidence you have in yourself. And remember, it’s not only about the destination, but also on how you get there!

      Good luck and let me know what you decide.

      Van Williams

  3. Hi Van, love your tutorials, they’ve helped a lot.
    Currently finishing up the insulation on our 09 Chevy Express 2500 cargo, all going well so far, but now I gotta map out the ventilation before going further. I’m installing a roof vent but my question is about your choice of floor vent location. I see you considered the length of the riser on the step but rejected it, choosing instead to build a duct between two walls. I’m no kinda handy, but it seems kinda complex when compared to cutting a square in the step riser, covering it with an adjustable vent, maybe an air filter? What am I missing?
    Thanks again!

    1. Great to hear from you!
      I don’t think you’re missing anything. The choice I made was purely based on my van (Ford Transit) and my personal preferences. Generally, I has three choices for a floor vent:
      One of the rear corner columns in the Transit, that have easy access to outside floor air without much metal cutting. I decided against that, because it was too close to my roof vent location (also in the rear) and the greater possibility for exhaust gases to enter the vehicle.
      Then the riser (step-in) area:
      Great location (maximum distance from rear roof vent for better natural convection), easy access and as you said, easy to cut a hole. Some negatives: visible when you step in and in my case, the area under the vehicle where the vent would vent into, may receive a water tank at a later stage, which would make things complicated for me.
      I chose for the wall cavity purely for the hidden properties and the access underneath that was already there. But that’s an option, only available on the new Transit.
      The riser area is a good location, just make sure that it won’t block anything underneath.

      Good luck with your conversion, keep in touch and perhaps send me a few pics when you’re done with the floor vent.

      Van Williams

  4. I remember seeing your floor vent ages ago and forgot where I’d seen it but not where you’d put it. I recently did something similar. I’m in a pop-top that is my daily driver and I have kept the height standard with a very low profile roof from GTRV and a removable roof rack, which is added for adventures. My van is 7’2″ and fits in some city parking and gets into all areas in National Parks. I am fitting a fan to the fresh air intake and relying on the vented windows in the pop-top to allow hot air to escape. Thanks again for the inspiration. You can see it on my IG feed:

    1. Good to hear that you found some inspiration and things worked out that well. While I installed the floor vent already some time ago, I haven’t been able to test the airflow yet. My Ford Transit has fixed windows all around and I haven’t got my roof vent installed yet. I do know that my dog likes to be close to the vent, while driving. I’ll be working on the roof vent soon and then I will find out whether I need an extra fan in the floor vent or whether the fan in the roof vent is sufficient. How is your experience with the airflow?
      Happy travels!

      Van Williams

  5. I have a 2016 Ford transit 350HD thinking of installing 2 floor air vents right behind the wheel wells .each will be 2 inches.but I’ve been told it’s better to have on big hole for air vent.what do u think

    1. Dear Raul:
      I don’t know about the size, but smaller is better than nothing. You can also use an in-line fan to increase their efficiency. What I would worry more about is that generally, there are more exhaust fumes towards the rear of the vehicle that could enter through these vents and make it unsafe. Usually a roof vent is installed in the ceiling at the rear of the van. The ability for ‘natural convection’ to develop between the floor and ceiling vents improves with a larger distance between the vents, making the case to place the floor vents towards the front of the vehicle. That, of course, wouldn’t be if you install a roof vent close the vehicle cabin 🙂
      Van Williams

  6. I read somewhere to install 2 powered roof vents. one in rear and one up front. Operate one on exhaust and one on intake

    1. Hi John,
      It isn’t bad advice and you see it applied in many van conversions. Beside the extra cost, there are many theoretical and practical differences, between that and the combination with a floor vent.
      The two vents is a mechanical solution, where air is forced from one point to the other. With the floor vent one can opt for natural convection; the cooler air from under the van (inlet positioned lower than outlet) will be drawn into the van by natural convection by the warmer air in the van that rises and leaves the van through the ceiling fan. Using the single fan in the vent, can only help the movement. The air entering is often 10-15 degrees Fahrenheit cooler than from the ceiling which is exposed to the sun. Air circulation will also reach the floor level.
      Double fans are well-suited for extended length vans, less for medium-length and not for a standard van. One always looses precious solar panel space on the roof and a second vent is another power user in a 12V-110V limited environment.
      You cannot loose either way, but it is a personal choice, based on the type of van, you have in mind.

      When we are talking about ventilation, insulation and other temperature or moisture related subjects, one can only do so much and living in a van in summer is hot and humid, no matter what you do. The only solution for that, is to change elevation throughout the year. Stay in a low desert or Florida in winter and at 6000-9000 feet elevation in summer. Follow the seasons.
      Van Williams

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