Jonathan Bates is better known for the food forest he and his colleague Eric Toensmeier planted on their 1/10th of an acre urban lot in Holyoke, Massachusetts. When I visited him in February, most of the lot and its 200 plant species were still covered with snow, but Jonathan showed me around their eco-shelter. Thanks to good insulation and thermal mass, the passive greenhouse maintains above freezing temperatures all winter, and allows them to grow food throughout the year.