Wrapped in his coat, Matt Braverman stood beside the earthen bags, his tools slung across the earthen floor. The rotting husks of summer’s garden clung to the fence – sunflowers frozen in a winter storm.
A subcontractor with Bad Goat Forest Products, Braverman was just hours away from finishing what many believe will be the first passive solar greenhouse in Missoula.
When the project is complete, Braverman will shed his winter coat and watch the greenery unfold around him, never mind the season.
“The idea is, the sun will hit the earth bags all day long and during the night, they’ll radiate back the heat and maintain a more even temperature,” said Braverman. “They’re thinking they’ll be able to use this all winter.”
Framed with sustainable Montana wood products, walled with bags of dirt and roofed with two-ply Solex panels, the greenhouse should extend the growing season by months, boosting the yield of the university’s campus garden.
A novel approach to gardening in northern climates, the project began almost accidentally. The university’s Farm to College program wanted a greenhouse, but it couldn’t cover the expenses on it own.
At the same time, members of the annual Senior Class Gift campaign were looking for a cause to commemorate UM’s 2012 graduating class. Past classes had purchased a campus bike rack, planted trees on the Oval and placed a campus map for hikers on Mount Sentinel – tough gifts to top with minimal funding.
But then came the idea of a greenhouse – a gift that keeps on giving. More than 150 seniors donated $20.12 each for the cause in 2012. It wasn’t a ton of cash, but when the Farm to College program matched it, the combined funds covered the $6,000 expense to build the greenhouse.
“We know seniors can’t give large amounts because they’re still in school,” said Tara Udall, who runs the Senior Class Gift program with the UM Foundation. “We’ve never raised enough to gain traction for something of substance. But this collaboration couldn’t have worked out any better.”
Not unlike a strawbale house, the walls are stacked with sandbags filled with dirt. The roof’s south-facing slope, covered with two-ply Solex panels, is angled to catch the winter sun.
The transparent panels allow sunlight to filter in, trapping the heat while warming the earthen bags. When the winter sun fades and the cold sets in, the bags of dirt should serve as a heat sink, releasing subtle warmth back into the room.
“Because of the passive solar design, we hope to have enough heat in the winter to grow cold climate crops like kale, lettuce and spinach for the salad bar,” said Ian Finch, the program coordinator with UM Dining Services. “It’ll be a place to start all our seedlings for this campus garden.”
Use of the greenhouse could expand in the years ahead. UM’s master gardeners hope to locate more space on campus to grow edible products, and most of the seedlings will germinate here in the warmth of the new greenhouse.
“We’ll be able to grow through the winter and start growing so much earlier,” said Finch. “We’ll be able to grow here during the summer, too, even after the other plants get moved out to the fields – the warm-weather crops like tomatoes.”