What is a Deep Winter Greenhouse?
A Deep Winter Greenhouse (DWG) is a greenhouse designed to limit the amount of fossil fuel it takes to grow crops during cold winters. DWGs are passive-solar greenhouses that rely on energy from the sun to heat the building instead of more traditional heating sources.
There are a few important aspects of the design that make this possible. DWGs are built in an east-west position, with a glazing wall that faces south. This wall can be specially angled, depending on latitude, to get the most possible solar energy on the coldest day of the year. The sun heats the air inside which is blown underground with a fan and stored in a thermal mass made of rock or soil. This heated thermal mass acts as a heat battery and stores heat for when it is needed at night.
DWGs in Minnesota can be used to grow crops that thrive with minimal light, providing year-round production capacity for small-scale farmers and gardeners. Crops well-suited to DWG production include a variety of lettuces, herbs, brassicas, Asian greens and sprouts. The UMN Extension Regional Sustainable Development Partnerships have two DWG designs, the DWG 2.2 and the Farm Scale Deep Winter Greenhouse available for download.
This Farm Scale Winter Greenhouse is appropriately scaled to offer small and medium sized farms the opportunity to grow vegetable crops for sale year-round. The greenhouse primarily uses the sun’s heat which is captured and stored in a thermal mass. These plans offer different options for thermal mass storage, foundations to accommodate different budgets, and comfort levels with complexity. Though the greenhouse uses solar heat, it will also require an additional backup heat source.
These documents reflect design changes incorporated as a result of the statewide prototype 2.0 initiative.
For those who are looking to build a DWG on a budget, this report explains some of the techniques used by experienced DWG producers to build your own affordable structure for winter production.
Carol Ford, Chuck Waibel
Supported by RSDP, the Northlands Winter Greenhouse Manual provides detailed and easy-to-read construction specifications for building a DWG in northern climates as well as production techniques for successfully growing crops.
This guidebook highlights the successes and lessons learned by growers across the Midwest who have designed and built cold-climate greenhouses to grow produce during the winter with minimal reliance on fossil fuel-based heat.
This report is helpful for urban and non-profit organizations that are looking to build a DWG. These case studies will explain some of the extra considerations that might be necessary.
ATTRA, National Center for Appropriate Technology
This site contains a large amount of useful information about solar greenhouse design.
This lightening talk demonstrates the basic principles of DWG technology using an 8' by 11' model.
Producers can use these tools to estimate the revenues and expenses they might expect with a DWG enterprise.
This research report examines the ability of DWGs to be viable business models. Results are based on analyses of eight deep winter producers in Minnesota in the winter of 2017-18.
This enterprise budget allows users to examine potential costs and revenues of growing early season tomatoes in a DWG. The enterprise budget uses an Extension early season tomato research trial as the basis for cost and production information.
Learn how to grow winter hardy crops in your Deep Winter Greenhouse.
This is a list of crops that producers have found to work particularly well in the DWG system.
Get advice and tips for building and laying out shelving for planters in a DWG system.
This report provides recommendations for DWG producers using passive solar technology for cold tolerant crops like leafy greens.
Summary and recommendations from Deep Winter Greenhouse tomato production trails in 2021-2022.
Expanding the use of Deep Winter Greenhouses for summer tomato production: feasibility and profitability
Production and feasibility research results from 2021-2022 DWG tomato production trials.
Year one research trial results of DWG horticulture trials in DWG prototypes.
This poster displays results of analyses of various potting soil mixes for the common DWG crops of mizuna, arugula and giant red mustard.
This poster highlights research results on day/night temperature effects on kale plant growth.
These case studies provide the stories of three different DWG producers. Learn what inspired them to build a DWG, what drives them to produce, and lessons that only those with experience can tell.
This report highlights progress on a variety of research projects underway to look at the potential to maximize winter vegetable production. Results of analyses of day-night temperature effects on plant growth; vitamin C content of different fertilizer mixes; light response curves of kale; and vitamin C depletion rates are included.
This poster was presented at the Midwest Organic and Sustainable Education Services 2015 annual conference. The poster highlights results from trials that examined the performance of different fertilizers used in winter production.
Growing in a Deep Winter Greenhouse
In this Marbleseed Ag Solidarity Network video, Greg Schweser, Dan Handeen and Carol Ford present an overview of the Deep Winter Greenhouse program, providing a background on how the program came about, design and construction strategies and a primer on growing winter veggies.
Deep Winter Greenhouse: Heat storage systems and their trade-off's
DWG webinar from 2021, featuring Shannon Mutschelknaus (Wayward Springs Farm) and Dan Handeen (UMN Center for Sustainable Building Research). They share their experiences concerning heat storage and thermal mass applications in passive solar winter greenhouse systems.
Deep Winter Greenhouse Designs: DWG 2.0 and Farm Scale DWG
In this webinar from June 5, 2020, Dan Handeen explains the designs of the older DWG 2.0, the new Farm Scale DWG, and takes questions from the audience.
Growing plants in the deep winter greenhouse
This webinar from June 2, 2020 features Carol Ford and Shayne and Louise Johnson of Grampa G's Farm. Get a video tour of Shayne and Louise's DWG and learn about how farmers use these structures to grow winter vegetables.
Growing plants in deep winter greenhouses
This webinar from May 28, 2020 features Carol Ford and Brooke Knisley of Alternative Roots Farm. Get a video tour of Brooke's DWG and learn about how farmers use these structures to grow winter vegetables.
DWG research convening: November 4, 2016
Current and future DWG producers, RSDP staff, and University faculty, students and researchers discuss past projects and research and future research needs.
Watch the seminar or download the presentation (PDF). The 2016 DWG research convening summary provides an overview of the research convening and a list of project ideas and research topics that participants identified.
DWG history, design and future aspirations
University of Minnesota College of Design researcher Dan Handeen presents to the Minnesota Renewable Energy Society on this history, design and future aspirations of the DWG project (September 2016).
DWG research seminar: November 4, 2015
DWGs: An overview
A quick overview of DWG pioneer and author Carol Ford's DWG that presents the general concept of the technology.