Foam Insulation in Windows

Dear Priuschat:

Thought some people may be interested in this mod. Attached is a photo showing my blue 2011 gen 3 Prius. It has a plug-in mod from Boulder Hybrids with 4 kWh LiFePO4 batteries. But this post is about the windows.

I was heading to California from Colorado, was planning on sleeping in the car during the trip and wanted privacy and possibly reduce some heat to the inside of the car. Didn't have the cash to spring for window tinting but I did have some foil backed 1-1/2" thick foam insulation. Using a hacksaw blade I cut the insulation to fit snugly in all the rear windows, foil facing out. This took some trial and error for the main rear hatch window, but eventually was able to carve the insulation to fit. I used some foil backed tape all around the cut-outs edges which kept those little while balls of insulation in place. I didn't do the bottom hatch window which is nicely tinted. I can still see cars behind me through that window in the rear view mirror. I also cut some insulation to place behind the front seats for privacy from the windshield perspective. If I was to do it again, I would just use a piece of cardboard, the rigid insulation was a pain to constantly install and remove. Photo attached.

This was the middle of July, 2016 going through Colorado, Utah, Nevada and California and then back the other way. At one point I stopped at Dinosaur National Monument on the boarder of Colorado and Utah and measured the roof and window temperatures. I was using an infrared temperature sensor. The roof was 160 F and the windows were 130 F with the insulation, 120 F without the insulation. The insulation was making the glass hotter, as would be expected. I also noticed condensation happening between the windows and insulation in the morning after sleeping in the car. This could be a problem long term because that moisture isn't designed to be on the inside of the car. It tended to be collected at the bottom of the window and go into the door, which is OK for a little while. I didn't see any water damage on the rear hatch window.

The inside of the car was bearable in hot Nevada rest areas where I opened the windows then rested as needed. Without the insulation, that car would heat up in a second even with the windows down. At night I would leave the car running and have the outdoor air blowing into the car with the windows closed. This kept fresh air moving into the car. The car engine turns on periodically to charge the main traction batteries. In the winter I have successfully used this strategy all night long to keep the car warm enough for sleeping. Engine turning on when the oil temperature was low, then turning off. I wouldn't recommend it during hot summers because an engine can overheat if needing to run air conditioning for long periods uninterrupted. A board placed behind the passenger with the back seats down can make for a nice long platform in the Prius for stretching out. I use a couple of patio chaise lounge pads for lying down upon.

Hope this is interesting to someone.

Best Regards,

energyideas

 

Thanks for the replies so far.

Also forgot to mention that I am 6'-4" tall, push the front passenger seat all the way forward and tilt it forward. Then put an extra wood platform in that straddles between the lowered back seats and the front arm rest between driver and passenger seat. Makes for a long platform to sleep. Helps if the back of the car is slightly higher.

Best Regards,

energyideas

 

Eastside: Thanks for the message. Radiant barrier is amzazing stuff, if used properly. It reflects longwave radiation. I didn't want my own body heat being reflected back while inside the car, I wanted to reflect the sun's heat. The sun is reflected to the window, and any long wave that passes through the window. This is why the window heats up. Radiant barrier is effective if placed 0.5" away from a surface. If mounted right on a surface it has no effect (has to do with the length of the wave). Any more than 0.5" and air currents, convection, transferes heat where you don't want it.

I know an alluminum foil window looks crazy, but I was staying in some crazy places, so the car costume was OK by me if it put any dobut into people's minds....

energyideas