MINNEAPOLIS — On a cold, colorless day in Minneapolis, an oasis is quietly growing in plain sight.
"You walk in and your lungs fill with humidity and greenery and there's a hammock where you can hang out if you want to," said Daniel Handeen with the Center of Sustainable Building Research at the University of Minnesota.
"I have taken one nap in here," said Jose Luis Villasenor, founder of Tamales y Bicicletas. "I'm only going to admit to one nap in here."
Villasenor and Handeen gave KARE11 a tour of one of the only two, specially-designed deep winter greenhouses in the state. This one, located at E 28th St and 15th Ave S in Minneapolis, sits on a lot leased by Tamales y Bicicletas, and has helped the urban farming non-profit fulfill its mission of combating food insecurity.
"We have some heavy greens, cilantro, jalapenos and other peppers that we're growing here in the deep winter greenhouse," Villasenor said.
Deep winter greenhouses save energy thanks to a design that maximizes passive solar energy. This one features three heavily insulated walls and one giant, south-facing, glazing wall, which captures heat from the sun.
Once captured, an underground duct system helps store and circulate the heat.
"The warm air rises up to the top," Handeen said. "It gets drawn in via these inline duct fans, and then we draw the hot air down into a network of tubing that's in the soil right underneath our feet. That heats up the soil and acts as kind of a thermal battery."
Handeen works with the University of Minnesota Center for Sustainable Building Research and says - like any battery - the ground still needs a charge, and sometimes that requires a little bit more than what the sun can offer this time of year.
"We've got insurance essentially," Handeen said, pointing toward one of two small heaters. "In this case it's a two-stage electric heater that's set on a thermostat that basically kicks on whenever the thermostat gets below about 55 degrees."
But despite the cold and clouds on Friday, the thermostat inside the greenhouse still hovered around 60 degrees. Over the course of the winter, Handeen says this greenhouse will end up using about half the energy of a conventional greenhouse of the same size.
"Last year our monthly energy bill was like $200," said Villasenor. "I thought these things were going to have to be on on a regular basis, but the sun, even on a cloudy day like this, we're still getting some heat."
The design is showing so much promise that the University of Minnesota Extension Service is now taking applications for a farm-scale deep winter greenhouse partnership opportunity, which offers $25,000 to help farmers outside the metro area build and maintain similar greenhouses for the next three years.
"I think you're going to see these across Minnesota," Villasenor said. "Initially, I was totally skeptical. I was like, 'How are we going to do this?'"
But two years in, he says seeing is believing.
"(Plants) grow kind of thin in here, but they grow pretty well," he said. "I mean, this cabbage right here, last year we actually donated up to about 50 pounds, of veg that came out of here twice last winter, to food shelves in North Minneapolis.
Applications for the farm-scale deep winter greenhouse partnership are due by February 14th. For more information, click here.
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