A New Hampshire environmental center proves that solar technologies aren’t just for low latitudes and sun-kissed climes.
For the naturalists at Tin Mountain Conservation Center, getting close to the earth is more than a job requirement—it’s a way of life. Whether leading school bird-watching trips, sifting through swamp muck with young summer campers, or developing forest management plans as part of an intensive ecology course, the TMCC staff has always been more at home in the outdoors than in an office.
Founded in 1980, the nonprofit advocates environmental preservation through earth science education and outdoor activities. The organization hosts an array of educational programs and summer camps in schools and communities throughout northern New Hampshire and parts of Maine. After years of renting office spaces and even running programs from the trunks of staff members’ cars, the organization is finally settling into a proper home—an 8,500-square-foot facility in Albany, New Hampshire, designed to reflect the TMCC’s environmental mission and fully use the few sun-hours the site receives.
Set on a 138-acre sanctuary acquired through donations and in conjunction with a local land trust, TMCC’s new Nature Learning Center was completed in August 2006. Twenty different locally harvested woods were used for the framing and finishes. But a major feat is that this northern New Hampshire building meets nearly all of its energy needs with solar energy produced on the roof.
The $1.9 million facility provides a long-overdue home for the organization’s administrative offices, as well as a classroom lab, library, great room, small kitchen, and two conference rooms. The new center is a hub of activity, with as many as 300 people passing through during any given week for various field trips, lectures, and events.
It took more than a decade of planning to bring the project to fruition. The architecture firm of Christopher P. Williams of Meredith, New Hampshire, led the design effort, working with TMCC to realize its vision. Initially, the budget dictated passive solar options, but partway through the design, one of the project backers advocated a more active approach—and offered to pay for solar-electric and solar hot water systems.
The high latitude (43.96º N) and tree-filled site posed big challenges. In many portions of northern New Hampshire, the sun is only visible above the tree line for about three hours per day for much of the year—that is, when it shines. And this site’s winter solar window—from 10:30 a.m. to 1:00 p.m.—left little room for design error.
Determined that it could be done, the backer/donor sought out Steven Strong of Solar Design Associates, a renewable-energy design firm based in Harvard, Massachusetts. While other installers and engineers shied away, saying that there was not enough sunshine at the site to produce adequate solar energy, Strong saw the potential and signed onto the project as a design consultant for the mechanical and solar systems. He was confident not only that solar energy would work for the facility, but that it would meet most of its energy needs. His strategy: obsessive and aggressive efficiency.
“We set an energy target of net zero, and collaboration with the architect was key to meeting that goal. The architect must be on the same wavelength as the solar system designer. If they aren’t, then you can’t get there,” Strong says. “We were fortunate to work with an architect who fully understood the importance of elevating energy efficiency to the top of the priority list and that every single decision—from concept to construction—needed to be made with energy consumption and solar in mind.”
TMCC’s only request was that the systems not detract too much from the site’s natural beauty. Having already chosen locally grown white cedar for the exterior siding so that the building would blend with the wooded site and complement the nearby barn, TMCC staff hoped that the systems could be integrated in a way that demonstrated both the functionality and beauty of solar energy.
Strong suggested that both systems be integrated into the roof—essentially becoming the roof—rather than using the traditional approach of mounting the solar systems on top of the roof. Applying the same techniques used in commercial glazing applications for skyscrapers and storefronts, the custom “sloped glazing” design utilizes the PV modules and solar hot water collectors as the weatherproof barrier.
TMCC staff and board had a small case of sticker shock when they learned that the design and installation of such specialized systems would cost close to $300,000, but with the donor willing to pay a premium to make it happen, there was nothing holding them back. While the cost for an integrated system was significantly higher than traditional roof-mounted systems, Strong convinced TMCC that the integration would pay off in the end—both aesthetically and financially.
“A roof made from PV and solar thermal collectors will last longer than most conventional asphalt-shingle roofs,” Strong says. “So, while an integrated approach is more expensive up front, it all probably works out in the end when you consider the cost of repairing and replacing an asphalt roof—and having to pay someone to remove and dismantle your system to do those repairs.”
The new solar plan required considerable changes to the original building concept. Williams returned to the drawing board, changing the angles and dimensions of the roofs to better accommodate the PV and solar thermal arrays. Among other efficiency upgrades and mechanical modifications, vents and air space also had to be added in the eaves to allow excess heat to escape. Fortunately, the original design already included a basement, which easily accommodated the mechanical and electrical for both systems and the backup boiler.
Large areas of south-facing roof accommodate the solar thermal and PV systems. On the south roof of the great room, sloped at 40°, flat-plate collectors with low-iron tempered glass make up the 1,200-square-foot solar thermal array that feeds the radiant floor heating and the 1,500-gallon storage tank in the basement.
Forty-three 300 W Schott modules are wired in seven subarrays and integrated into adjacent roofs. The upper story roof’s five subarrays slope at 30°, while the porch roof with two subarrays slopes at 12°.
Key to TMCC’s “near net-zero” electricity footprint are New Hampshire’s fairly progressive net metering rules. All utilities are required to offer net metering, and unlike many states, net excess generation is carried over to the next billing period indefinitely—meaning that any summer surplus can be used in the darkest days of winter, until all the credit is used up.
It is because of this carryover that the gentle roof angles, which help to maximize summer production, make solar work well for this building. “With New Hampshire’s indefinite carryover, it’s actually a disincentive to angle the roof for winter harvest, and it’s best to maximize production during the sunniest times of the year—late spring, summer, and early fall,” Strong says. “You have to make hay while the sun shines. Here, it doesn’t much matter when you produce solar energy just so long as you do.”
Alternatively, he had hoped for a steeper roof angle for the solar thermal array, which would optimize production during the winter months when the sun is low in the sky and demand for hot water is highest. Mounting the collectors at latitude plus 15° (tilted about 60°) might have produced about 4% more energy in winter (October to March). Summer production would have diminished slightly but not enough to affect the load coverage. But only so much could be done with the layout and geometry of the structure since each roof section had to fit with the style of the building.
In place of traditional oil or electric space heating, a radiant floor heating system was chosen, along with two heat recovery exchangers and a high-efficiency multifuel boiler for backup. Individual zone controls allow for greater heating control throughout the building. One of the challenges with solar heating in this region is that when the heat is needed most, it is often cloudy—so backup heating is crucial. Finally, a wood-burning fireplace helps heat the nearly 1,500-square-foot great room.
Passive solar design elements were also incorporated. Large south-facing windows help passive gains, while smaller windows on the north side help reduce heat loss. Aligning primary activity areas—great room, library, and some offices—along the east-west axis allows those rooms to gain passive heat in the winter. Overhangs shade southern glass from the summer sun, and window positions allow for cooling cross-ventilation in most spaces.
The real key to the “net zero” design is the thermal integrity of the building envelope. Spray-in polyurethane foam and blown-in fiberglass insulation are used in the wall and roof cavities throughout the building—except in the great room, where timber-frame construction supports 6-inch-thick structural insulated panels that have an R-38 insulation value.
At the foundation, layers of fiberglass and foam insulation keep frost at bay. Custom-built doors made from local hardwood and double-pane argon-filled windows prevent drafts. The great room’s fireplace—built of stone from the site’s abandoned quarry—includes an exterior thermal break, as well as throat and chimney-top dampers to minimize heat loss.
Despite a few glitches along the way, mainly linked to the installation of the boiler and an undersized circulating pump for the tank, both the solar-electric and solar thermal systems are working flawlessly, says Michael Cline, TMCC’s executive director.
Now in its third year of occupancy, TMCC is meeting nearly all of its energy needs with solar energy produced on site. In 2008, the PV system generated 13,500 kWh of electricity. The total used by the building was 14,000 kWh, resulting in an shortfall of 500 kWh purchased from the local utility (Public Service of New Hampshire).
Meanwhile, the solar thermal system continues to provide about 75% of the space heating and domestic water heating needs, with the remaining heat provided by second-growth wood cut from the property—about four cords annually used for the boiler backup system. Perhaps best of all, no fuel oil has been used in two years.
Home Power Associate Editor Kelly Davidson recently conducted a do-it-yourself energy audit on her apartment in Takoma Park, Maryland. As a renter, she cannot replace the old doors and windows, but she’s doing what she can to seal air leaks and reduce phantom loads.
Tin Mountain Conservation Center • www.tinmtn.org
Christopher P. Williams Architects • www.cpwarchitects.com • Building design
KW Management Inc. • www.kwmanagement.com • Installation
Solar Design Associates • www.solardesign.com • PV & solar thermal system design
PV & SHW System Major Components:
Schott • www.schottsolar.com • PV modules
SMA America • www.sma-america.com • Inverters
SunEarth • www.sunearthinc.com • SHW collectors
Taco • www.taco-hvac.com • Circulator pumps