I am a big fan of self-sustainability, if such a thing even exists. I want to grow my own food (lots of it) all year around. I would also love to do it with a minimum of fertilizer and water. Not that water is especially scarce where I live, but it can get expensive. At my old house in Easton, PA, using a hydroponic system, I was able to maintain a 60 sf garden on 5 gallons of water per week during the heat and dry of August, and all of that water was collected in my rain barrel. Not a drop came out of the hose that summer, and I got a good amount of delicious produce, although it was just a small experimental garden.
My new greenhouse will be a dome. After seeing the one at the Rodale Institute in action, I just had to have one! This is my second homemade greenhouse after my first attempt at urban gardening. With a new home in the country, I have more space for a bigger greenhouse! This one will be about 18 feet in diameter.
Another extremely important requirement is heat retention. I want to be efficient with both water and energy, and the greenhouse must not freeze even during the coldest of days in January. After considerable research, I have settled on an insulated foundation with a subterranean air heating system. For this I will need to dig to our 36" frost line.
I have the excavator ordered for delivery this Saturday, but I have no idea how I am going to dig a round foundation to line with pink board.