Deep Winter Greenhouse

The Deep Winter Greenhouse: Environmentally Friendly production all year long

Buying local leafy greens seems improbable during Minnesota’s frigid winters. However, CSA members and some winter farmers markets are seeing this change, all thanks to the Deep Winter Greenhouse. Developed by the University of Minnesota College of Design Center for Sustainable Building Research, the Deep Winter Greenhouse is intended to help limit the amount of energy needed to grow cold-hardy crops such as lettuces, herbs, Asian greens, brassicas, and sprouts during the winter.

Alternative Roots Farm in Madelia is on their first year of operation using the Deep Winter Greenhouse. “We thought it would pair well with our long-term vision,” said Brooke Knisley of Alternative Roots Farm. They increased their fall Community Supported Agriculture (CSA) program and added a winter CSA. “Growing in the greenhouse has proven rewarding, as well as a fun challenge,” continued Knisley. “Our winter CSA members have been enjoying their baby salad greens and microgreens immensely. Our microgreens have been a hit at our local co-op and winter market.” The farm also plans to host educational workshops, along with open houses for the public to learn about the greenhouse.

Grampa G’s in Pillager is coordinating with the University of Minnesota Extension Regional Sustainable Development Partnerships to build a greenhouse soon.  We spoke with Shayne Johnson about the benefits that they forecast with the project. “We have been to many open houses and have seen that it is proven to work,” said Johnson. “This will provide year-round opportunities for us to sell to our customers in Pillager that do not have access to fresh greens at the [winter] markets.”

Deep winter greenhouse showing the transparent side of the building.
Deep Winter Greenhouse at Alternative Roots Farm

Side of a deep winter greenhouse. Grey solid building with white door and small window near roof.

Click photo to take a virtual tour of Alternative Roots Farm's Deep Winter Greenhouse.

 

Environmental factors are another benefit. Johnson noted that the University of Minnesota has successfully supported the progress in technology and developing the “next generation of high tunnels.” The farm currently utilizes solar high tunnels to prevent the soil from freezing. However, high tunnels do not protect against greens that have already grown above the soil. Unfortunately, it only takes one freeze to destroy these crops. Alternatively, an enclosed Deep Winter Greenhouse uses solar energy to heat the inside up to 100˚ F during the day. At night, the stored heat releases into the greenhouse and keeps the temperature between 45˚ F and 50˚ F. They are also more precise and efficient with water and energy compared to a typical greenhouse or the field.

Daniel Handeen, a researcher at the Center of Sustainable Building Research, shared that the most significant factor that the greenhouse is addressing is energy consumption. “We are trying to make as much use of the sun's light and heat energy as we can, all while keeping the environmental control systems relatively low-tech, and the construction materials relatively low-impact,” said Handeen. The solar energy created within the greenhouse will allow farmers to have better control of the temperature there, leading to more control of the energy consumed.

Handeen explained that the solar panels are placed directly south at a 60˚ angle, capturing the maximum amount of sun on the coldest days of the year. There is a duct on the ceiling that will capture the hottest air that has risen. This air will then be sucked to the ends on the building, and finally drawn to the back of the greenhouse (north end) and into a 4-foot rock bed under the surface. Heat transfers through the rock, and comes up through the air ducts, preserving the stable temperatures within the greenhouse. For more information about the design, click here to access the complete blueprint of the Deep Winter Greenhouse or review the air circulation schematic.

Extending the growing season is beneficial to both farmers and consumers. “It has been a fun new adventure,” exclaimed Knisley. “Growing in the winter adds to the whole operation because as the season winds down, we would like to still be growing vegetables.” Handeen hopes to see “decentralized, high-quality, low-energy food production” within neighborhoods across the state all year long with the installation of more Deep Winter Greenhouses. Thank you to Alternative Roots Farm, Grampa G’s, and Daniel Handeen for your work researching this new innovation and producing fresh produce for Minnesotans.

Airflow schematic for deep winter greenhouse.
AIR FLOW SCHEMATIC Courtesy of Grampa G’s Farm and the University of Minnesota