You would not in any way pay for that much insulation and windows in 10 years, not even close. My home is significantly larger than theirs and I maybe pay about $2000 a winter to heat it and next to nothing in the summer to cool it because I’m stubborn and just use a fan or two. And that’s heating with propane and electricity Mostly leaving the thermostat at 70 since I don’t have a smart thermostat, I could get that cost down by more than half if I used wood. They’re paying around $40,000 premium on tons of insulation and high end windows. They also bought solar panels to run the heat pump. But even excluding the solar panels it would take at least 20 years to get back their investment and then that time they could’ve turned that $40,000 into more like $100,000 in a high-yield mutual fund. Since they have solar panels they could off and heat their house with free electricity if it was of traditional construction instead of sealed up like a bank fault meaning they’d probably spend a lot less and not even recoup their money in 30 years let alone the opportunity cost of investing that money.