Build a $300 underground greenhouse for year-round gardening

A giant cold frame!
Utilizes the green house effect of glass.

http://www.natureknows.org/2013/11/build-300-underground-greenhouse-for.html

Growers in colder climates often utilize various approaches to extend the growing season or to give their crops a boost, whether it's coldframes, hoop houses or greenhouses. Greenhouses are usually glazed structures, but are typically expensive to construct and heat throughout the winter. A much more affordable and effective alternative to glass greenhouses is the walipini (an Aymara Indian word for a "place of warmth"), also known as an underground or pit greenhouse. First developed over 20 years ago for the cold mountainous regions of South America, this method allows growers to maintain a productive garden year-round, even in the coldest of climates. Here's a video tour of a walipini that even incorporates a bit of interior space for goats: Read More: http://www.natureknows.org/2013/11/build-300-underground-greenhouse-for.html

-----

Of course, there are precautions to take in waterproofing, drainage and ventilating the walipini, while aligning it properly to the sun -- which the manual covers in detail. Read More: http://www.natureknows.org/2013/11/build-300-underground-greenhouse-for.html

-----