Where to place the vent-fan on roof of van

[livewire516]

Originally Posted by aerohead

Does the van have a headliner, or is it just a stripped cargo van?
The reason I'm asking is that, with a radiant barrier and some insulation, you could really knock down the radiant, infrared load during full sun.
A white exterior roof ( if it didn't already have it ) would reflect much energy away before it had any chance to convert to long-wave radiation.

So yes, it's a cargo van stripped down and the exterior color is white. Right, the solar gain isn't much, and I still do plan to install a layer of insulation on the ceiling. Unfortunately, no other windows open besides the driver- and passenger-side windows up front. So at least in the immediate term, (and more so from a moisture/mold/mildew perspective) some forced air will be necessary.

Thanks for the link to the canopy drag thread - it looks like one of those forms could be replicated and at least reduce it's Cd while closed.

[j-c-c]

Originally Posted by aerohead

Drive naked!

In that situation, Seinfeld, George, and shrinkage comes to mind with a good A/C solution.

[cRiPpLe_rOoStEr]

Originally Posted by livewire516

and more so from a moisture/mold/mildew perspective

So maybe the best spot to fit the vent-fan would be closer to where moisture accumulation is more critical.

[aerohead]

Too bad there isn't a small dehumidifier available, scaled to the volume of the van.
Here in North Texas it isn't necessarily the dry-bulb temp. that gets you, it's the latent heat. ' Pestilential swamp' as Howard Hughes say.

[livewire516]

Yeah, managing the climate of a living space is much more than just air temp.

I once lived on the top story of a flat-top roof building. My stand-alone A/C was oversized for the room and would run full blast but it didn't matter: The thermal mass of the 'tar beach' above me radiated through the ceiling and practically baked me throughout the night! I was so tempted to sneak a hose/sprinkler up there...

Intuition says I get more utility from secure passive ventilation than the aero penalty from driving since most time spent in the van will be when parked. But as I mentioned earlier, I might look into several smaller vents that protrude less at a later stage.

[aerohead]

wow! that's delicious!

[cRiPpLe_rOoStEr]

Originally Posted by livewire516

I might look into several smaller vents that protrude less at a later stage.

That's the best approach. I usually see it on campervans, and even on some ambulances.

[nemo]

"tar beach"
Needs some of this highly reflective passive cooling paint.
https://pubs.acs.org/doi/10.1021/acsami.1c02368

[livewire516]

Originally Posted by nemo

"tar beach"
Needs some of this highly reflective passive cooling paint.
https://pubs.acs.org/doi/10.1021/acsami.1c02368

Some cities in the US are offering incentives for property owners to paint their roofs white. It is of course a trade off between reducing passive solar heat gain in winter vs reducing peak AC demand in summer, so it only makes sense in certain climates and situations. In my previous career, I worked for an NGO that focused on modifying the built environment; our main clients were city and state governments - it was my job to engage with private property owners and negotiate incentives. The economics that drive energy-efficiency decisions are fascinating.


(I wasn't directly involved with the energy efficiency; my funders were typically Depts of Public Health).

[livewire516]

Originally Posted by cRiPpLe_rOoStEr

That's the best approach. I usually see it on campervans, and even on some ambulances.

You're right - I already own the roof-mounted fan, but it's still new-in-box so I really shouldn't treat it like a sunk-cost. I should be able to sell it and recoup most of that money spent. I skimmed around RV & Van forums; here's an interesting thread where people discussed low-profile and inconspicuous van ventilation:

https://www.cheaprvliving.com/forums...ion?pid=120830

Another option I ought to consider is replacing the fixed rear windows with the hatch-style windows that were offered in the passenger-version of these vans.

https://www.youtube.com/watch?v=Xuhjcx348ck

Truthfully however, I would like to do away with the rear-doors' glass entirely, something that isn't so easily broken into (even though I don't plan to keep valuables in the vehicle, someone would have to break in to figure that out for themselves). But a similar hatch mechanism would be nice with a panel of a different material.