Partially Underground Greenhouses

Interesting article with a link to a paper on the "Walipini", which are greenhouses partially dug into the earth. Good for colder temperatures and growing at the upper latitudes where you have a shorter season for plants.

http://csglobe.com/underground-greenhouses-year-growing/

http://opensourceecology.org/w/images/1/1c/Walipini.pdf