This is a view of the Earthship before the Greenhouse was built. You can see the first couple of rows of tires being pounded. The tires for the greenhouse have to be at least as deep as the frost line which in Durango is 32 inches.
The Earthship Greenhouse is the one of the greatest things about the Earthship. It allows the home to remain warm all winter long. Our house has not gotten below 60 degrees for the past two winters even though the outside temperature has been as low as -5 degrees Fahrenheit.