Insulating an Unconditioned Attached Garage for a New EV?
I live in Colorado, just got a EV and noticed that the battery is not as efficient when the car is soaking in cold air overnight in my 3 car unconditioned attached garage (bedroom above) that has no insulation in the walls, ceiling or roof. I started to think what if I insulate the walls and then add a ceiling with insulation at the bottom of the trusses and insulation to the garage doors as well, perhaps that will help keep the garage warmer in the winter even though it is not a conditioned space. We have one electric car and one ICE car, when the ice car comes into the garage and it is 20°F outside the ICE car will warm the garage about 1.5°F degrees for 3 hours so inside the garage will go from 32° to 33.5°. My thought is when the garage is insulated it might keep it a bit warmer. When it got to -7°F the other night outside, my garage was 18°F so there must be some heat radiating from the attached house and along the heat in the concrete floor keeping it 25°F warmer.
But then I started to think batteries also do not like to be too hot also, in the summer the garage can get very hot, which is not good for the computer in the car and the car will turn on fans or AC to limit the hot temp (therefore wasting energy). By insulating the garage would I be making the garage even hotter creating an even larger issue because now it is draining the battery to cool the inside of the car? Or by adding plenty of soffit vents around the garage perimeter along with the existing large vent at the top of the roofline would that keep the roof cooler and therefore the garage cooler as well?
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