A deep winter greenhouse is a heavily insulated greenhouse designed with a steeply sloped south-facing glazing wall to capture solar heat in the daytime, which is drawn underground and stored in soil or rock for use later in the night. (Courtesy of the University of Minnesota Extension)

The University of Minnesota Extension Regional Sustainable Development Partnerships (RSDP) will partner with five farms in Greater Minnesota to conduct research and outreach on the newest farm scale deep winter greenhouse design.

One of the farms selected for demonstrating the newest farm scale deep winter greenhouse designs is Tintah Beach Farm in Thief River Falls.

This project, supported by a Minnesota Department of Agriculture program, brings together small- and medium-scale fruit and vegetable growers in Minnesota with University of Minnesota researchers and designers to develop the next generation of innovative, sustainable winter food production technology.

Marcus Langevin, operator of Tintah Beach Farm, said the farm has already completed a majority of the building foundation and the below ground climate battery system. He estimated final completion will be in September 2025.

“Through reinvention of old methods, today’s human-scaled farm operations are able to achieve high yields with minimal waste,” said Langevin in his application. “This increased efficiency results in a reduced area of land requiring cultivation, and lessens the required off-farm inputs. While the construction of a farm scale deep winter greenhouse (FSDWG) would require significant resources, the improved design shows the most promise in being an economical solution to reduce winter fuel inputs for heating a growing space. I commend the University of Minnesota Extension Regional Sustainable Development Partnerships (RSDP) in the work they have done in promoting, researching, and developing this type of structure. In a relatively short period of time, this program has become a resource for many other growers in colder climates, not just those in our state.

“My initial interest in the concept of a deep winter greenhouse,” said Langevin, “started before I had even heard the term. I had learned of earthships in the early 2010s, which utilize similar design elements to grow food in one’s own home. Since then, I had learned about Walipini greenhouses as well as forest garden greenhouses before learning of the first prototype DWG being built in the mid-2010s. Since then I have revisited the concept and have been really excited to see different versions as they get introduced. Tintah Beach Farm is committed to help demonstrate in a production model how these could solve the nutritional food needs of Minnesotans.”

The five farms selected through a competitive process are:
• Tintah Beach Farm in Thief River Falls • Chelsea Morning Farm in Two Harbors
• Marvin’s Gardens in Melrose
• New Story Farm in Hutchinson,
• Owl Bluff Farm in Houston, Minnesota

These five farms will build the newest version of the farm scale deep winter greenhouse designed by the University’s Center for Sustainable Building Research.

What is a Deep Winter Greenhouse?
A deep winter greenhouse is a heavily insulated greenhouse designed with a steeply sloped south-facing glazing wall to capture solar heat in the daytime, which is drawn underground and stored in soil or rock for use later in the night. This structure is optimized for growing cold-hardy crops throughout the winter such as brassicas, Asian greens, and lettuces. Some growers are experimenting with more exotic crops such as ginger, turmeric and tropical perennial fruits.

“The new farm scale deep winter greenhouse builds on previous versions, but reduces construction costs by utilizing a simpler underground thermal mass system to store heat,” said Greg Schweser, director, Statewide Sustainable Agriculture and Food Systems, RSDP. “The new greenhouse is also scaled more appropriately for farmers who grow crops for sale at local markets. With low-energy input winter food production, growers will increase their revenues and Minnesotans will have year-round access to fresh, locally grown, healthy foods.”