I’m very interested in maximizing passive cabin cooling, both at rest and in motion. Here is a list I’ve come up with, along with some thoughts on each item. This list assumes a near-worst case scenario. Imagine the vehicle sitting in the hot Arizona sun.
- Paint car/roof white
Self explanatory. White paint reflects a lot of sunlight. I’ve personally had extremely positive experiences with elastomeric white roof paint.
- Tint/film on windows
Virtually eliminates heat transfer through windows in motion, and significantly delays it while stationary.
- Reflective sunshades in windows (when parked)
Self explanatory.
- Light colored interior
Reflect more sunlight/heat. I’m a big fan of beige.
- Dark colored headliner
Improve reflected sunlight/heat capture from the light interior, and improve transfer thru to the cool white roof. Basically traps heat up high, where it’s easy to get rid of it.
- Evaporative cooler
Especially in dry areas, and even more especially if it can be plumbed into the vent system on the firewall, downstream of the blower motor. Fill with water, turn the blower motor on, and voila.
- Solar vent system (while parked)
Install a vent fan in the ceiling, pulling from the shaded area underneath the car, creating a draft through the interior and (potentially) evacuating the hottest air.
I’d like to add that stationary passive cooling is very important, it extends the lifespan of your car interior, and also improves interior conditions when you get in the car. For something with no A/C, any passive improvement is very valuable, and even with A/C, a passively cooled vehicle reduces cooling requirements, maximizing MPG and/or power on hot days.
So—any other ideas?