Cozy Acres Greenhouses: Operating With Zero Emissions

Cozy Acres Greenhouses: Operating With Zero Emissions

Cozy Acres Greenhouses_zero emissions

A 30-kilowatt photovoltaic system generates approximately 39,000 kilowatt hours of electricity per year for Cozy Acres Greenhouses.

In 2011, after more than 20 years in business, Cozy Acres Greenhouses owners Jeff and Marianne Marstaller knew they needed more growing space. In addition to wanting to add onto their operation, located in North Yarmouth, Maine, the owners also had a desire to explore a greener approach to growing. What resulted was the construction of a zero emissions greenhouse — a greenhouse that operates every day of the year and generates more electricity than it consumes.


The process started when Cozy Acres was invited into the Maine Farms for the Future program, which awarded Cozy Acres $25,000 to initiate a farm expansion program that would make them more profitable.

“This grant was very much appreciated, but it wasn’t enough to make the project financially feasible,” Jeff Marstaller says.

Cozy Acres had concurrently applied to the U.S. Department of Agriculture Rural Energy for America (REAP) program and was awarded 25 percent of the energy portion of the project, about $48,750, with $6,250 to be used for a geothermal upgrade in one of its conventional greenhouses, and $42,500 for the new greenhouse.

For the proposed greenhouse, Marstaller says “The overall premise was this: We would get the electricity from the sun, the heat from the earth and the emissions would be zero.”

Making Moves Toward A Greener Solution

Jeff and Marianne Marstaller started Cozy Acres in the late 1980s, using space in a business park to grow annuals. After buying seedlings the first year, they put up 17- by 96-foot Inflation Buster greenhouses to grow their own.

The business grew throughout the 1990s, supplying more garden centers and landscapers and building more greenhouses. By 2001, Cozy Acres had 21,000 square feet of connected, double-poly greenhouses with concrete floors.

From there, the business began selling its annuals, vegetables and herbs on a wholesale basis, delivering to garden centers and landscapers.

Marstaller says he knew the most recent expansion would depend on whether or not grant funding could be secured.

Applying for the REAP grant funds was an intimidating and lengthy process, and required Marstaller to arrange financing for the entire project, because REAP grant funds are not delivered until projects are up and running, he says.

By April 2012, Cozy Acres received word that it had been awarded the grant.

“We had earlier decided that moving ahead on the new building project would 100 percent hinge on receiving the REAP grant,” Marstaller says. “ If we didn’t get the grant, we couldn’t justify the expense of building a totally green greenhouse, and we probably would have just added another conventional greenhouse.”

Longfellow's Heat Curtain, Winter Microgreens_Cozy Acres Greenhouses_zero emissions

The heat in the radiant floor of Cozy Acres’ zero emissions greenhouse allows greens to be grown on the floor during winter months.

Creating A Zero Emissions Greenhouse

The first phase of the project was to have a 30-kilowatt photovoltaic system installed on ground mounts that would generate approximately 39,000 kilowatt hours of electricity per year.

The second phase entailed building the new greenhouse — a standalone 30- by 96-foot Conley greenhouse, glazed with 8 mm polycarbonate on the roof and two sides and 16mm acrylic on the two high-visibility sides. The greenhouse features double ridge vents and a side vent with a large double door on the south side, with room for expansion to the north.

A 10-ton geothermal system was installed along with the greenhouse, connected to a mile of one-inch poly lines buried 4 1/2- to 5-feet below grade behind the greenhouse. The concrete floor was poured over two inches of Styrofoam board, incorporating radiant tubing at 12-inch O.C. A small air coil fan unit was installed overhead, Marstaller says, but the majority of the heat is supplied via the radiant floor.

A meter located behind the photovoltaic panels records the electricity generated by the panels and feeds electricity back into a power grid in southern Maine. A second meter records how much electricity the entire property consumes, including all eight of the operation’s greenhouses, while a third meter located inside the zero emissions greenhouse records the power usage of only the electrical panel that feeds the greenhouse.

“We are given credits for the months we generate more than we use, and either we use those credits or outright pay the difference for the months we use more than is generated,” Marstaller says.

The heat in the radiant floor allows greens to be grown on the floor duing the coldest months.

“There are mornings when the outside temperature is -15°F to -20°F, and the temperature of the inside wall of the greenhouse is right at 32°F,” Marstaller says.

Cozy Acres only grows the plants that can take the low temperatures until March, when the spring vegetables and herbs are started. Around mid-February, plants are moved to the bench tops, when the nightly lows aren’t much below zero.

“Like most greenhouse growers, once the projected nightly lows are in the high 40s or more, I shut off the geothermal and save on my electrical bill,” Marstaller says.

By Memorial Day, the top vents, all the doors and the side vent are opened and circulation fans are shut-off.

“For the following half of the year, this greenhouse uses no electricity,” Marstaller says.

After passing two anniversary dates, Cozy Acres has seen between 38,750 and 39,000 kilowatt hours generated each year, Marstaller says.

“By generating almost 39,000 kilowatt hours annually, and the meter on the incoming line of the new greenhouse showing that we used less than 37,000 kilowatt hours per year, we have a zero emissions building,” Marstaller says. “As we look out on each cold morning and see exhaust and steam rising from the seven conventional greenhouses and none from the new greenhouse, we smile.”

Jeff Marstaller_zero emissions

Marianne and Jeff Marstaller

The Addition Makes Cozy Acres A More Marketable Property

Cozy Acres only uses organic fertilizers in the new greenhouse, and only once last spring was an OMRI-approved spray applied.

”Essentially, all of our insect control is through beneficials and predators,” Marstaller says.

Cozy Acres received organic certification for the new greenhouse through the Main Organic Farmers and Gardeners Association (MOFGA).

It has been expanding its sales into microgreens by supplying local restaurants, sandwich shops and vendors at farmer markets.

“Though the profitability of microgreens is marginal at best at our current level, as the sales increase, we anticipate mechanizing that process,” Marstaller says.

Cozy Acres also anticipates adding a 400-square-foot processing room this summer to meet increasing food safety regulations.

Marstaller says the true cost of the new greenhouse is hard to calculate. The process has required months of work, but Marstaller says they are very happy with the end product.

“We have done a little to offset the burning of carbon and have had many people thank us for our efforts and dedication to the green movement,”
he says.

The Marstallers say they are thinking about their own future, too.

“We are both turning 60 and won’t be doing this forever,” Marstaller says. “Building what may be the first greenhouse that is used and heated throughout the year in the northern part of the United States with zero emissions makes our property more marketable.”