The Main Idea: We would like to take winter vegetable production in Northern Minnesota to a new level. A number of other farms in our region have built "deep winter" greenhouses, a passive-solar design which successfully uses a warm air pumped into a heat sink underground to moderate temperatures (info on current designs). In a climate where we can reach -20 to -30 degrees and long stretches of sub-zero weather, we propose to add another heating layer to our friends' current designs by adding solar thermal panels. The greenhouse will allow us to grow cold-tolerant greens through the entire winter. We will complement these greens with storage crops from an attached root cellar, which is also part of the project. Since we are veterans of vegetable production in Minnesota, we feel this is the right move to extend our season and meet the needs of local eaters in search of good food at a time of the year when we most crave it. Backers can benefit directly by becoming members of our winter CSA or indirectly by supporting this low-energy solution to winter food production. We will translate our learnings to other farmers.
Project Size, Construction, and Technical Details: We have already moved a small cottage on-site and excavated for the greenhouse.
The cottage is situated on the edge of a hill and provides a ready back wall for the greenhouse. The hillside topography will provide more constant temperatures as we will be building well below the frostline. The greenhouse will stand 16 feet tall allowing for a steep angle to let in as much light as possible in the depths of winter. Four feet below grade we will build a super-insulated foundation where we will place tiling and rock for a solar air heat sink and the radiant floor tubing to be connected to the solar thermal panels. Since we already use our outdoor wood boiler for all our winter heating needs, this system will quickly tie into existing infrastructure and assure us of back up heat source when solar is not available. The greenhouse itself will be 32 feet long by 16 feet wide, a good size for a winter growing structure and will surely meet our needs for a modest 20-30 member winter CSA (in start up phase). We will cover the greenhouse with double-walled polycarbonate (as seen on original "Garden Goddess" greenhouse below), which retains more heat than plastic and is traditional in greenhouses like these.
The extra 9-foot by 14-foot space in front of the cottage and adjacent the greenhouse will be the root cellar. This is modestly-sized, however, scale appropriate for our off-season CSA and production. Currently some off-season crops are stored in a 6 x 6 alcove where our well pump sits - far from ideal. Like the greenhouse, we will use simple timber construction to keep the project at a somewhat low cost. After much research, the project will use evacuated solar thermal tubes for heating. These come in panels of 20-30 tubes and hit a higher temperature than flat plate panels, which will complement the high heat in our wood boiler. Since the cottage roof will extend 4 feet higher than the greenhouse itself, this will provide a perfect elevated space to catch solar in the depths of winter. In time, we can easily add other panels to this systems to add heating capacity, which would allow us to heat the cottage, possibly for farmstay purposes.
- $2,000 - Excavation
- $5,000 - Wood and building materials
- $1,500 - Polycarbonate sheets for covering
- $1,500 - Labor costs
- $800 - Rock and sand material
- $4,500 - Solar thermal system
- $800 - Radiant floor materials
How we are going to pull this off: I am friends with 3 other growers in the region who have constructed deep winter greenhouses, including Carol Ford who constructed the first in our region with her late husband Chuck Waibel of Garden Goddess fame. Now organized in the emerging Deep Winter Producers Association, there is a growing community of small-scale growers learning and building together. Chuck Waibel designed his first greenhouse to be built inexpensively using easily sourced materials. For example, my friends Sue Wika and Tom Prieve at Paradox Farm built their 16 x 24 greenhouse for $5,000 in materials. I expect our costs to be closer to $16,000 due to the added costs of the solar thermal system, increased size, and some hired labor. Jeremy Fischer, deep winter greenhouse technologist who helped construct Sue and Tom's greenhouse a year ago, will be chief mastermind for our project, so we have some direct experience on deck. Also, being a farmer, we have a knack for delving into projects and seeing them through. I think it comes from having to make it through a growing season year-in and year-out no matter what's thrown at us.
We are looking to kickstarter this project with $5,000+ and will make up the difference with sales from the farm and a line of credit at our local community bank.
Risks and challenges
There are two main risks related to this project: construction and deep-winter growing. I think we have the skills in place to overcome these risks.
On the growing front, we have over 13 years of experience growing produce commercially and operating a CSA. We have done some season extension in high and low tunnels and have been operating and maintaining a greenhouse for that same time. After this many seasons, we've seen a lot of issues and have the grit to pull through just about any farming mis-hap. As a worse case scenario, we know we can store crops with existing structures into December and grow crops in shoulder seasons (fall and spring) should unforeseen production issues arise. In this way, we will be able to fulfill our reward obligations, albeit at a slightly different time of year.
On the construction side, we have retained the services of Jeremy Fischer, deep winter greenhouse technologist to be our chief carpenter and designer. Jeremy has years of experience in both construction and growing and put up one of the few deep winter greenhouses operating in our region at Paradox Farm near Ashby. With this experience and the assistance of a large contingent of supporters, family, and fellow farmers who have already volunteered their help, we will get this thing built this year.Learn about accountability on Kickstarter
- (30 days)