Deep Winter Greenhouses Defy Minnesota Winters

August 19, 2021

As the summer winds down so does the typical growing season for Minnesotan gardeners and growers. But not for the five Deep Winter Greenhouses designed by Center for Sustainable Building Research (CSBR) Research Fellow Daniel Handeen.

Supported by the University of Minnesota Extension Regional Sustainable Development Partnership (RSDP), the Deep Winter Greenhouse (DWG) campaign saw the building and completion of five prototypes: Bemidji Community Food Shelf, Central Lakes College in Brainerd, Organic Consumers Association in Finland, Alternative Roots Farm in Madelia, and Lake City Catholic Worker Farm.

“I first worked with greenhouses as part of a 2014 Design for Community Resilience project for Eagle Bluff ELC in Lanesboro,” explained Handeen. After being awarded an Extension Block Grant that same year, Handeen continued his work to research, test, and design greenhouses.

The current DWG (version 2.2) is built with an angled, transparent wall that faces south to capture the heat from the sun. An underground rock bed below the greenhouse stores the heat, which then keeps the planting area warm at night. Crops can be planted directly into the soil as well as in suspended planters. “The performance of our original five greenhouses has exceeded my expectations,” said Handeen. “We have learned a lot about what to improve, but I’m always amazed at the conditions in the greenhouses when I visit them.”

One of the managers of the DWG at the Lake City Catholic Worker Farm, Paul Freid (pictured above), has also been impressed with the greenhouse’s performance. “Our experience so far has been really great! We grow greens in the fall and winter to sell on our kombucha stand on our farm and in the spring we start our veggie seeds and sprout ginger and turmeric. This summer we are experimenting with growing ginger and turmeric in the growing space and we are also experimenting with keeping some citrus trees year round to flavor our kombucha.”

Freid sees the DWG project as a key way to help support local food systems, the local economy, and food sovereignty. “We can grow healthy and delicious food right here and now. I think it can be a challenge, albeit a good one, to make them work financially. So food producers need to continue to experiment to see how they can maximize the use of the space.”

While the construction of the greenhouses was completed in 2018, Handeen and the RSDP team have continued their research. “We continue to gather data. Most importantly, we have temperature loggers inside and outside of the greenhouses. This lets us know if the greenhouses are staying warm enough and how extreme the cold is outside. Additionally, we track electrical usage for each type of appliance to see if and when the backup electric heaters are triggered during extended cold periods.”

As Handeen and the RSDP team gather data from the current greenhouses, there are a few areas of particular interest for future improvements. “We know the rock bed built below the greenhouses works, but we don’t really know if it’s the right size. It’s like we have an electric car with an oversized battery and still need to figure out what size the battery should be to maximize efficiency,” said Handeen. “The glazing on the transparent wall is another area for further improvement. Obviously, it is needed to bring in the sun’s heat and light, but it’s a liability in terms of heat loss. I was recently awarded a USDA Speciality Crop Block Grant to research and prototype thermal curtains that can insulate the glazing wall whenever the sun isn’t shining.”

Another area of investigation for the team is how to better integrate phase-change materials. “These are materials that store heat as they melt,” explained Handeen. “And then give off that heat when they re-solidify. Right now they’re cost prohibitive, but that is changing. I have some ideas for eco-friendly materials with simple storage methods I’d like to try out.”

Ongoing research of the DWGs has also spurred the creation of Farm Scale Winter Greenhouses suitable for small to medium-sized farms. Thanks to help from Homegrown Minneapolis and Sustainability at the City of Minneapolis, two organizations are currently building such greenhouses in the city: Appetite for Change and Tamales y Bicicletas.

“Minneapolis Health and Sustainability staff have been excited to learn through our pilot project partnership how well this greenhouse technology can support energy-efficient year-round growing for residents and support community resilience and food sovereignty,” said Tamara Downs Schwei, the Homegrown Minneapolis Coordinator. “Dan Handeen’s evolving and responsive design has facilitated a process and product that reflects community partners’ needs and goals, as well as the City’s. The nimble scale and structure of the greenhouse could enable more community residents access to learn, grow food, and stay connected throughout the year.”

Once in operation, these new Farm Scale greenhouses will allow operators to reduce costs and increase productivity, making them a more accessible option for growers. You can learn more about Deep Winter Greenhouses, Farm Scale Winter Greenhouses, and how to build one on the University of Minnesota Extension website.

Photos courtesy of Paul Freid.

Funders and partners in RSDP’s DWG work include the College of Design Center for Sustainable Building Research; Sustainable Farming Association; University of Minnesota Institute on the Environment; MnDRIVE; Minnesota Department of Agriculture; University of Minnesota Solar Energy Laboratory; USDA SARE; AgCountry Farm Credit Services; AgriBank; Compeer Financial; BFG Supply; Mattson, Macdonald, Young Structural Engineers; and DWG pioneers Carol Ford and Chuck Waibel.

For residents of rural Minnesota, eating sustainably year-round can be a challenge. This spring, a graphic design class created posters to promote a key link in the local food chain: small grocery stores.

Administered by the Green Business Certification Inc. (GBCI), the Sustainable Sites Initiative (SITES) Certification provides developers with a comprehensive rating system to help them design and build more sustainable projects.