Farming has always been a seasonal business.
Farming has always been a seasonal business. The length of a growing season is determined by the latitude at which a farm is located. The further north you go, the shorter the growing season, and the types of crops that can be grown becomes more limited.
This winter, a group of researchers from the University of Minnesota Extension Regional Sustainable Development Partnership (RSDP), along with the Center for Sustainable Building Research (CSBR), will test a prototype of a Deep Winter Greenhouse (DWG) in Finland, which is located between Duluth and Ely.
In 2014, the Southwest Regional Sustainable Development Partnership received a two-year, $76,000 grant from the Bush Foundation to develop a mutual assistance network of small-scale, sustainable food entrepreneurs using high-efficiency greenhouses in west central Minnesota.
Designed by former Montevidean Dan Handeen, a DWG will allow farmers to grow fresh produce through the winter months.
Handeen, who graduated from Montevideo High School in 1992, went on to earn a master’s degree in architecture from the University of Minnesota.
For the last 10 years he has been a researcher for the CSBR. The CSBR designs high performance residential homes and combines them with solar design elements to reduce a home’s carbon footprint.
According to Hometown Focus <www.hometownfocus.us>, “DWGs are passive solar, low cost, low carbon winter food production systems. Producers using DWG technology are able to grow winter-hardy crops such as lettuces, cole crops (e.g. cabbages, broccoli, Asian greens), and various sprouts with little or no added heat.”
Handeen designed the greenhouse to optimize the sun’s rays in order to keep the building warm during the winter. Built along an east-west axis, the south facing glazing wall is angled to catch the greatest amount of solar energy on the shortest day of the year, the winter solstice.
The prototype DWG will be 24 feet long by 24 feet wide. The R35 insulated walls will be built on a four foot deep, insulated cinder block foundation. A triple-glazed, poly-carbonate glazing wall will let the sun warm the greenhouse during the day.
An underground mass consisting of an insulated rock bed, perforated drain tile, and soil captures and stores heat during the day At night, the trappped heat from the day is released into the tile and circulated throughout the greenhouse by fans and vents.
“The idea for winter greenhouses has been around since the early 1900s, but there has been little interest in developing the technology due to the low prices of fossil fuels,” explained Handeen.
Handeen hopes to keep the materials costs under $7,000, making it affordable to farmers. Total cost for the greenhouse should be around $10,000.
Minnesota winters are notoriously cold, but Handeen has high hopes that his design will keep the greenhouse warm enough to grow crops. “I’ll be very happy if the temperature stays above 45 degrees,” he said.
The DWG will also have a supplemental heat source that will kick in on extremely cold days and strings of days when it is cloudy.
“The greenhouse is one step in reducing our dependence on fossil fuels,” said Handeen. “It’s also a way to stabilize our food supply.”
Handeen is excited about the prospects for DWGs. By combining low up front costs with the promise of year-round farming, he hopes that someday in the near future farmers will embrace the technology.
He mentioned that plans for the greenhouses will soon be available online for free from the CSRB. “The simplicity of the design will make it easy for farmers to scale up the size of the greenhouses if they want to grow more crops,” said Handeen.
Ground will be broken soon on the first DWG prototype to be built in Finland, and Handeen is looking forward to the results of this winter’s test.
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