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RSDP Happenings - Focus on Winter Production

November 2015

By Karen Lanthier

DWG Barn

Photo by Jody Radar.

With new funding from the University of Minnesota’s Institute on the Environment and increasing interest from growers, the UMN Regional Sustainable Development Partnerships (RSDP) continue to lead research and outreach on Deep Winter Greenhouses (DWGs) in Minnesota.

“The recent $50,000 grant from the Institute on the Environment allows us to advance the access to and understanding of DWGs throughout the state,” said Greg Schweser, Associate Director for Sustainable Agriculture and Food Systems at the Partnerships. “Our goal in the next phase of this project is to find partners and support the creation of five to ten demonstration Deep Winter Greenhouses that would be accessible to the public in different parts of the state, so interested folks can ‘kick the tires,’ and see how they operate while asking questions directly of producers.”

DWGs are a newly emerging technology that enable small scale producers to grow vegetable crops throughout the winter with minimal externally delivered fuels, thereby decreasing the carbon footprint for food production. In these structures, solar heat is captured from a south facing glazing wall and stored in an underground insulated rock bed that is laid below the frost line. Hot air is pulled into the ground with fans in the daytime and percolates up through the soil at night.

The smaller scale of these structures and minimal heat input costs make this technology accessible to a wider range of producers for whom conventional greenhouses might not be an option. Winter production offers small-scale vegetable producers the opportunity to produce products throughout the year, increasing the viability of their farm businesses.

Recently, the Regional Sustainable Development Partnerships hosted a public seminar to highlight ongoing research in DWG technology. The seminar attracted University staff, students, and members of the public from as far away as Grand Rapids. The proceedings of the seminar are available online on our Deep Winter Greenhouse resource webpage:


The Northlands Winter Greenhouse Manual

The Regional Sustainable Development Partnerships have been working with researchers and community partners to study production and building performance while also coordinating and hosting workshops to help others learn how to build and grow products in a DWG. The RSDP specialize in building community-university partnerships around technology and ideas that originate in the community. The Partnerships work in DWG kicked off six years ago on a collaboration project with Chuck Waibel and Carol Ford with the co-publication of the Northlands Winter Greenhouse Manual. Waibel and Ford had built a passive solar greenhouse in response to world-wide changing conditions related to climate, energy uncertainty, and diminished rural food access. Their book teaches others the principles of passive solar design and the horticultural approach required to grow in deep winter.

Since the Northlands Winter Greenhouse Manual publication, interest has risen steadily, culminating with widespread awareness and plans for adoption across Minnesota and beyond. The Partnerships have supported a variety of DWG projects over the years including:


Ongoing university research plans include a building performance study conducted by Dan Handeen with the Center for Sustainable Building Research. Handeen is conducting energy audits of functional DWGs and identifying possibilities to create a stronger shell that will be more energy efficient. Weaknesses have been found in building seams where glazing walls are connected to structures. Handeen is identifying solutions to this and other problems as well as recommending materials and products that will work most optimally in DWG environments. This work will culminate in the creation of construction documents that builders can use as guides when constructing DWGs.  “It’s often been surprising research for me, looking at the cost, longevity and environmental impact of different building materials,” said Ford. “What has been great about doing this work through the University is that we have so many experts we can call on who can analyze and test different materials, designs and business models. We can bring it all together and it rocks!”

Growing Trays

For those interested in learning more about DWG production, a day-long workshop will take place in conjunction with the 2016 Minnesota Organic conference on January 7. Carol Ford and others will lead this workshop that covers the more in-depth aspects of DWG production specifics, building design and performance, marketing, networking, and more.

Future RSDP work includes identifying potential funding sources for building research, demonstration, and outreach. By making DWG technology available on the landscape, prospective adopters of the technology can have a clearer understanding of how the system works before they make the leap. University research and public access to these facilities will continue to make this technology  more visible and well known among producers throughout Minnesota and beyond.
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