Blue's ceiling vent and fan work quite well when there is a door or window open, but don't work so well when Blue is all closed up. When sitting in the hot sun, it gets quite hot and stuffy inside. The best remedy I could think of was to add a floor vent. With a floor vent, turning the roof vent fan to the exhaust setting would draw air from the cooler underside of Blue, while blowing the hotter interior air out the roof vent. Even with the fan off, as long as the vent was open, there would be a natural convection flow of air from the cooler floor vent up through the warmer roof vent.
I had a few criteria for a floor vent:
There must be an easy way to close it when it's cold or when driving down a dusty road
It must be screened to prevent flying insects as well as mice or rats from getting inside
It must be large enough to provide reasonable airflow
It shouldn't be too intrusive
It should be located well away from the exhaust to prevent exhaust fumes from being drawn in when sitting and idling
I checked all the forums to see what other people had done, and while there were many who have added a floor vent, none of the solutions seemed ideal. After wandering around Home Depot (HD), I found my inspiration in the plumbing department - and if I had a nickle for every time that's happened...
I used 4” PVC schedule 40 threaded couplers to make the vent. To begin with, I cut a hole in the floor just large enough to fit the male threaded part. The hole was located just forward of the bed on the driver's side, which is forward and on the opposite side of the exhaust pipe. Before drilling anything, I checked underneath at least six times to make sure I wasn't about to drill into the fuel tank or a brake line. Then I drilled a small pilot hole, and again checked the location. When I was positive that the location was right, I drilled a larger hole, then used a metal blade in my jigsaw to cut the round hole.
The screens were done in two parts. My brother Paul cut a circle out of a heavy metal lattice we found at HD. The diameter of the lattice was just slightly larger than the ID of the PVC, and he used a hammer to force it into the male coupler. This would be the barrier for the more aggressive vermin like mice, rats and raccoons.
He also cut some nylon screen material and bonded it to the top of the female coupler to keep the ants, flies and mosquitoes out.
The plan was to insert the threaded part of the male coupler up through the floor from underneath, then screw the female coupler onto it until the two halves fit tightly against the floor. A PVC cap would be used to close the vent when desired.
To lubricate the threads, several wraps of teflon tape were applied, and to ensure a good seal between the floor and the couplers, a bead of silicone sealant was applied around the bottom and top of the hole. Then the male coupler was positioned and the two parts were screwed together and tightened against the floor.
The PVC cap, after a little sanding, fit nicely over the top of the couple, effectively sealing it off from the outside.
At this stage in Blue's evolution, the vent is rather unobtrusive – sort of hidden under the overhang of the bed. The plan for a later version of the upfit is to build a floor to ceiling, vertical cabinet that will enclose both the floor vent and the composting toilet vent, as well as provide more storage. The bottom section of the cabinet will be louvered to allow air flow through the vent.
So far, after a few thousand miles of travel with our floor vent, and after camping in temperatures ranging from the 100+ degree heat in southern Arizona to the 30's in parts of California, we're happy with it. When we leave Blue parked in the sun and forget to open the roof vent, it is as stifling inside as any other parked car, but if we open the roof vent, Blue's interior is noticeably cooler. Additionally, when we hit the sack at night, turning the roof fan on cools the interior down considerably.
For the most part, the only time we close the vent is on dirt roads. We learned this lesson in Organ Pipe National Monument in Arizona after taking a 29 mile drive on an unpaved road. We spent the next week cleaning the dust and dirt from the outsides, insides and contents of all the storage bins under the bed.
As I write this blog, however, we are in Oregon on a rainy, raw day. The high is forecast to be 49 degrees and the low is predicted to be close to freezing. This was a good day to maintain the interior heat as much as possible by closing the roof vent and capping the floor vent. Then we wimped out and got a hotel room.