We have always included a solar greenhouse as part of our homes. Our first one in 1983 was an attached greenhouse with leaky French doors that separated it from the house. It worked great when the sun was out and it was cold but was a comfort deficit when it was hot in the summer. It did help buffer the cold at night and on cold cloudy days, though it could not compensate for the leaks and low R-values in the envelope of the house. It isn’t that we didn’t pay attention to details as much as that we didn’t know what the details were. We did remodel it and add an active solar water heater system for the thermal storage tank but that was an engineering experiment. We got the collectors from a bankrupt company after Reagan eliminated the incentives for renewables. I was hoping for hot tub temps and got luke warm. It was pretty nice in late spring for about a week.
Our second greenhouse was a more educated guess and was attached to the daylight basement level or our passive solar house. It connected to the 8 inch poured concrete walls that served as a trombe wall that transferred heat into the house and solar storage that kept the greenhouse from freezing. We realized we used the greenhouse enough for the added production it gave our gardens and landscape to make it worthwhile. We have lived in different cities at different times but always built our homes in the country where we could have extensive gardens. Hopefully by growing a significant portion of our food we are offsetting much of our increased transportation needs in terms of carbon cycling.
When we built our present house we didn’t question whether to have a greenhouse. We were completely hooked by that point. This one is detached as the site would not put up with an addition on our south. It does not add heat or humidity to our house directly though it does hold our solar hot water collectors. We insulated the North wall and added metal 55 gallon drums filled with water for heat storage as well as the masonry for a planting bed and counter top. A solar greenhouse has the advantage over a hoop house because it does not need supplemental heat except on a few days when the temperature drops after a couple of cloudy days in winter. We have kept one pepper plant going for over 3 years. We bring a potted Meyers Lemon tree in each fall and it is now over 4 years old and produces around a dozen lemons a year. Even if it produced no lemons the experience of walking into the greenhouse in mid February and it being warm and filled with the scent of Lemon blossoms is worth the effort. We are able to start most of our garden sets, and have a steady supply of greens and lettuce all winter as well as early sweet peppers and cherry tomatoes. I have never done a cost benefit calculation though I imagine it pays off. It is a great source of entertainment and being able to work in the garden through the winter in a teeshirt is worth the effort.