MATT GENTRY The Roanoke Times

From left: Justin Boyle of Green Valley Builders; YMCA volunteers Jason Pall and Craig McNally; and retired Virginia Tech physics professor David Roper work on a solar greenhouse in Blacksburg.

A pilot project sponsored by the YMCA at Virginia Tech may turn the concept of seasonal eating on its head by making it possible to grow local food 12 months a year.

Traditional greenhouses shelter plants from frosts and trap heat from the sun to extend the vegetable growing season in cool climates.

But a "solar greenhouse" under construction off Maywood Street could make year-round local food production possible, Blacksburg environmentalist Dave Roper said.

Roper, who has been a leader in Blacksburg's Cool Cities and other sustainability projects, began researching solar greenhouses in 2006 as part of his family's quest to reduce their household greenhouse gas emissions.

"We're transporting food an average of 1,500 miles. In the wintertime, it has to be farther. That takes a lot of energy and fuel," Roper said. "Locally grown food is better. But how do you do that in the wintertime?"

One answer may be constructing greenhouses that use stones or water to store heat from the sun underground and then circulate it through the greenhouse as temperatures drop during the winter months.

The retired Virginia Tech physics professor -- who drives an electric-powered truck with its own solar panel to reduce consumption of coal-fired electricity -- sketched out a plan for building a year-round greenhouse based on more primitive designs used in China and Colorado.

In 2007, Roper went to YMCA at Virginia Tech director Gail Billingsley with the idea of building such a greenhouse as a model to encourage homeowners, neighborhoods and local farmers to boost production of fresh, local food.

The Y was at the time working with Arlean Lambert of New Jersey on a plan to relocate its community gardens to 15 acres off Maywood Street that Lambert inherited from her parents. Lambert has since pledged to donate her land to the Y, Billingsley said.

Plans are to double the size of the community garden and add an orchard, the solar greenhouse and a trail to the property. All will be done organically and with an eye toward environmental sustainability.

An anonymous donor then put up seed money to begin work on the solar greenhouse. Builders and other businesses chipped in with materials and expertise, and others have stepped forward to help with construction. Billingsley said the number of volunteers could top 150.

It works like this: The 18-by-32-foot greenhouse is built atop what's called a "heat sink." Some such structures use black barrels filled with water to absorb solar energy.

But the Blacksburg greenhouse will instead use a system of underground pipes sandwiched between layers of stone to store heat. A temperature-controlled fan system will then circulate the heat to keep the greenhouse at a constant temperature, Roper said.

The Y is already fielding inquiries from researchers, growers and homeowners interested in the concept, Billingsley said.

At an estimated cost of $35,000, the greenhouse project could seem out of reach to the average homeowner. But Roper said the design can be adapted to smaller spaces and recycled materials, which could bring costs down significantly.

Organizers hope to begin planting test gardens in January.