You've got insulation that is way beyond most of us. And you confirmed what I was saying, "you have to know all the factors to make a comparison." Sorry I missed the wind in the first comment and it would sure account for a much more rapid heat loss. No lights on in my house at night, but the comment on my garage failed to note that I have a freezer that would provide some heat. Don't know how much. We heat a well insulated building about 8' by 8' with a 7' ceiling (one window and door) with a 100W bulb. In most cases it stays at 40-50 degrees with less than 12 hours of light time down to 5-10 degrees. Below 0 we usually run a small heater set at 45 degrees but it doesn't come on very often.