Insulating an Electric Car

Today was unseasonably warm. It seemed like a good time to quick get some pre-winter work done. So, I took a shot at insulating my electric car.

Overall, I love my Mitsubishi iMiEV electric car. The big shortcoming to it is that the heater isn’t very good. I fixed that by installing an ethanol burning heater that connects to the stock heater system.

However, I’ve also found that the car is essentially NOT INSULATED at all! On a typical gas car, there’s a real firewall between the front of the car and the driver’s legs. In front of that is a nice hot engine that not only pumps out heat, but also acts as a giant wind-block. Not only is the iMiEV NOT a gas car, but it’s rear-wheel drive, so there’s almost NOTHING in front under the hood!

In fact, if I stick my head down by the driver’s foot-well, I can directly see daylight in several places. These are all conduits for cold air to blow straight in to the car all winter! So, my plan was to add some sort of insulation to help block the wind and keep some heat by my feet!

I already had some “radiant barrier” insulation for some other projects. This is basically double-sided bubble-wrap with a layer of aluminum on both sides. The bubbles insulate while the aluminum reflects heat back to where it came from.

The driver’s foot-well is roughly two feet wide. So, I cut a piece of the insulation about two feet wide by four feet long. The idea was to run the insulation under the floor mat and then all the way up and under the dashboard, cutting slits or holes in it as needed for the accelerator and brake pedals. I rough fit the insulation, and it looked like the idea would generally work. I was able to cut two slits and get the insulation around the brake and accelerator.

After working with it a bit, I decided that it sure would look nicer if the insulation was UNDER the carpet. On the left side, all I had to do was pull off two pieces of trim, so I did. I was then able to slide the insulation under the carpet without undoing the plastic trim of the center console. The insulation did bulge a bit around the styrofoam triangle where the driver’s left foot rests. I cut the insulation there to better shape it. It just took a little work to get the insulation to fit the carpet well. Once that was done, I put the carpet back.

I tested the steering and pedals to make sure the insulation didn’t bind or restrict any of those. I pulled the insulation back from the steering just a little to prevent the two from rubbing against each other.

Overall, it looked pretty good, but there was still a large uninsulated area directly under the dashboard. I cut another piece of insulation about two feet wide by a foot long and tucked it under the dashboard. There are enough various lips and edges under the dash that I could simply stuff the insulation under there and it held quite well. Of course, I did double check for any exposed circuitry. Because the insulation has aluminum on the outside, it’s a conductor, and I made sure it wouldn’t contact any power.

I only used just a little bit of duct tape to pin up the insulation in total. I think that zip-ties would work well too. There’s plenty of places under the dash that could be used as anchor points for zip-ties.

With all the insulation under there, I took the car out for a test drive. There’s no rubbing of the insulation against the accelerator or steering, but I couldn’t find a great way to fully insulate around the brake pedal without the insulation being in contact with it. The insulation does NOT prevent proper use of the brakes, but I can hear it flex and make a bit of a crinkle noise when I pressed the pedal. I also set the heater to full blast to make sure the insulation didn’t block the air-flow.

Overall, it looks good! You can’t see the insulation that’s under the carpet, and you can’t see what’s under the dashboard unless you actually stick your head under there. I’m hoping that the new insulation helps keep the cold outside air from getting in by my legs, and that whatever heat my body makes is getting reflected back to me.