Before I built a barn shop/office in 1989, I did a lot of reading about passive solar in buildings.  From that information I decided to include openable windows at the peak of the barn roof.  They are opened in the Spring and closed in the Fall.  A open window up high in the building with a source of air down low will create a natural draft.  Hot air rises.  That worked so well in the barn building that I did the same thing in the house when it was built in 1998.  The house windows are in a cupola up so high they had to be electrically operated.  The natural air flow does an excellent job of cooling the house in our climate.

Using what was learned from the barn and the house, I suspected that it might work in a high roof van.  In the sold Sprinter I cut a 3 1/2" x 4 1/2" hole in the floor just in front of the driver side rear wheel.  The location was selected so cool air flows past the refrigerator coil on its way up and out the open Maxxair roof vent.  Cooling the coil reduces the run time of the refrigerator.  The hole in the floor worked.  When putting your hand down at the floor vent hole you can feel the air flow.  Normally I do not power the Maxxair and rely on the natural air flow for cooling.

In the Transit build a 4" square hole was cut in the floor in front of the driver side rear wheel well.  A 1 1/2" thick frame was fabricated around the hole above the floor.  The frame was made out of two 4" long pieces of 80/20 extrusion and two 7" long pieces of 1 1/2" square wood.  The center hole in the extrusions was tapped and the wood pieces were bolted to the 80/20.  That created a 7" square frame with a 4" square hole.  The 80/20 used did not have a slot on the top surface and had a slotted bottom.  Two holes were drilled through the floor for mounting the frame to the floor.  Two carriage bolts were used.  The sandwich was the frame on the top, the van floor in the middle and a screen below the floor.  The floor hole location is shown on drawing # ODJ127-23 which can be viewed on the FLOOR page.

 

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The wood blocks have two 5/8" diameter wood dowel posts that are used as guides for the 3/4" plywood cover.  The dowels are 8" long including the 1 1/2" in the wood blocks.  The method used to open and close the cover is a replacement lawn mower starting cord.  Cord is attached to the plywood cover, goes up through a 90 degree 1/2" conduit bend and out to a hook on the cabinet wall.  When hooked the vent is open and when unhooked the cover falls by gravity to close. Did have to add another piece of wood on top of the plywood to make cover heavier.  Cover can be operated from the bed platform or from the aisle.  There is a foam gasket glued to the top of the frame.

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It was interesting that the vent did not work as well if the front cab windows were partially open.  The hole and open Maxxair will reduce the interior van temperature.  I know immediately when entering the closed van on a sunny day if the vent and Maxxair were open or closed.  With the floor hole and a Maxxair the vents can be left open when it is raining.  95 % of the time the floor hole is left open.  Do close it sometimes in winter at night when it is cold or if I drive on a dusty road.