Best thing to do is strip a car apart. They never account for insulation yet they do on sealing for water. Technically they could take the doors and spray a layer of foam in them and then do the same for the roof. You have another issue. It's the glass. Look at the percentage of the glass as compared to the total cabin. It's a pretty good amount and then it's at the top. After all of that, they need to make cars as light as can be, as for your house, it doesn't matter. So heavy materials that have a better R value along with the insulation (which takes up a bit of room) makes your house quite different than a car. The problem with EV's is that they have to replace ICE which allow for comfort since the energy to heat it, is essentially free and for an EV, its not at all, it's a liability. Even for AC as the engine makes much more in excess than what it takes to drive the compressor. If it takes 3 hp to drive the compressor and you have a 100hp engine, the chance you are using the engine at 100% capacity is rare. In addition to that, most cars today run the compressor all of the time and just use a valve to control what it does. The days of the electro magnet clutches are going away. I think we need to rethink HVAC and insulation when it comes to EV's to make them practical for all of the US for 365 days per year. It'll happen but it's going to take time.