A House That Gives More Than It Takes
Designing and building a passive solar house in the North Country was a family affair.
Tom and Nancy Southworth’s Cape-style house in Lancaster produces about twice the electrical energy it uses on an annual basis.
After almost thirty-seven years in the old farmhouse near the mill they ran in Lancaster, Tom and Nancy Southworth decided it was time to move someplace smaller and quieter—although still close to their grandchildren. “We wanted something really small and efficient enough that either one of us could live here into our nineties,” Tom says.
The resulting one-story, modern, Cape-style house—finished in 2011—stands in a flat valley in Lancaster with Mount Cabot and other peaks visible in the distance. It’s a lovely, livable North Country retreat; in addition, it’s a solar, net-zero Passive House that produces approximately twice the electrical energy it uses on an annual basis.
This wasn’t the Southworths’ first foray into high-efficiency housing, nor into building. Since 1974, when Tom and Nancy purchased the historic Garland Mill, an 1856 water-powered sawmill in Lancaster, Tom has built numerous homes, barns and other structures. In 1977, Tom’s brother Harry Southworth became Tom’s partner in the mill business.
In 1986, they founded Garland Mill Timberframes, a Lancaster construction business that uses the timber supplied by the mill. This company is now run by Tom and Nancy’s son Ben Southworth and his cousin Dana Southworth, who is Harry’s son. The company specializes in high-performance homes and heavy timber-frame structures. One of its projects is New Hampshire’s first LEED Platinum-certified renovation of a home on Squam Lake that was featured in Giving Back to the Grid in New Hampshire Home, March/April 2010.
The mill itself—the only one of its kind still operating in New England—has been a net electricity producer since 1982. It generates excess power (when not milling), which is sent into the grid.
A Passive House with presence
Tom, Nancy, and Ben all knew that the planned home was going to be high performance (“It needed to be if I was going to build it,” Ben says). But Tom and Nancy proposed taking things a step further. After reading a magazine article about Passive Houses, they asked themselves: Why aren’t we doing this?
Ben was excited about the idea but wasn’t a certified Passive-House builder at the time. There would be a learning curve. “My parents have always been very willing to try new things and to take risks. They thought, ‘This looks like an interesting opportunity,’ and they knew it would be for me,” Ben says. “I said, ‘Great! Let’s do it!’”
Even though Ben and Tom had high-efficiency and even net-zero building experience, a Passive House provided a very different challenge. A net-zero home uses an amount of energy on an annual basis that is basically equal to the amount of renewable energy created on its site. “A drafty house with a load of solar panels could be net zero,” Tom says. But it wouldn’t be very efficient.
A Passive House doesn’t have any energy-production requirements, but is built along relatively simple but hard-to-achieve guidelines for energy efficiency. These guidelines—which originated with the Passivhaus movement in Germany—include thermal protection, air tightness and ventilation with heat recovery, as well as efficient appliances and lighting. The house’s internal temperature is supposed to stay between 68ºF and 77ºF year-round.
“Passive House is mostly about the enclosure system, insulation, south [facing] windows and especially tightness,” Tom says. “The idea is that the sun heats up the inside through the windows and the enclosure is so incredibly tight that none of the heat leaks out of the building.”
Ben began by tackling the Passive-House precertification protocol, which involves submitting a design for a house that looks, on paper, as though it will operate according to Passive-House principles. “That was pretty tough,” Ben says. Luckily, he was able to hire a friend who was a certified Passive-House designer to assist. “He helped me navigate this thing,” Ben says. “I would fill out the protocol and send it to him when I got stuck.”
Although efficiency was a priority for Tom and Nancy. “We wanted the house to be aesthetically pleasing,” Ben says. Nancy—an artist by training who has a good eye and a feel for spatial relationships, according to Tom—was instrumental to this process. One way to achieve both efficiency and beauty was through the use of windows that let in the sun to warm the house while affording views of the mountains and forest. “Mom and I did a lot of work with the windows,” Ben says. Nancy originally wanted the windows in the family room/dining area to be floor to ceiling, but along the way, the family decided to incorporate window seats, which were suggested by the thickness of the walls. The windows are still quite tall.
Another consideration was the location of the house. Tom and Nancy chose a ten-acre lot just six hundred yards or so from the mill. The site—former home to a gravel pit and evergreen farm—had a pond, good solar exposure and excellent access to nearby grandchildren.
Once the location was set, the next challenge was to figure out the orientation of the house. The Southworths knew they needed a long roofline facing south. “Nancy and I spent a long time sitting out there on stones trying to figure out where to put the house,” Tom says. “We had the luxury of time.”
The eventual site (15 degrees west of due south for optimal solar orientation) offers great views and plenty of sun. The latter is not only necessary for Passive Houses, Ben says. “It’s good house design. People are heliocentric. The more sun we get—particularly in this climate—the happier we are.”
Nancy Southworth’s book bindery occupies one room of the house. Here, too, natural light is plentiful.
Construction began on a six-room house (plus bathrooms, a screened-in porch and a pantry) of about 1,700 square feet. The construction team consisted of the Southworths; mill workers Matt Hammon and Scott Cramer (who did the framing, tile work and most of the cabinets, with assistance from Tom); additional mill workers from time to time; and subcontractors for excavation, plumbing, plastering, etc. Harry helped build the house as well but passed away suddenly in December 2010.
The house is on a slab and has very thick walls; a Passive House is first and foremost a super-insulated house. It has forty inches of cellulose insulation in the roof, twelve inches of foam under the floor, and twelve inches of cellulose inside and two inches of foam outside the walls. One of the more challenging design considerations for a Passive House is that it must have a minimum of penetrations (other than doors and windows) for things like chimneys and plumbing vents.
The house has a 7 kW solar array on the south-facing roof. Hot water is provided by an 80 ft2 SDHW collector. For heat, there is a very small woodstove and five small electric heaters that are seldom needed. In the living room and kitchen especially, there is heat from the sunlight that pours in through the large windows. These are made in Canada from low-iron glass that allows for more heat transfer than most American homeowners desire. In Lancaster, “we’re a heating climate,” Ben says, “not a cooling climate. Most of this country is a cooling climate. Very few Americans live within a few hours of the Canadian border.”
When required, shades allow for the reduction of the amount of heat and light entering the building through the south-facing windows. Such shades are also a Passive House design requirement.
In this tightly insulated environment, and given the threat of house-rotting moisture that occurs where heat meets cold, an HRV (heat recovery ventilator) is a must. The system brings in fresh, cold air and preheats it with the outgoing moist air from the building. Carbon dioxide levels—a proxy for indoor air quality—are also continuously measured.
Cross-ventilation is a key feature that was carefully designed into the house. When the screen porch at the west end of the house and the kitchen door (and bindery windows) at the east end are open, outside air flows through the main living area from west to east.
The building materials for this special house were quite common, Tom says, with standard wood framing, etc. The exterior siding is untreated Eastern white cedar from a small mill in northern Vermont. The team salvaged where they could. The beech floorboards, for example, are from wood that had been sitting unused in a barn next door.
The spaces inside the house are simple and easy to navigate. A large room at the east end of the house serves as the headquarters for Nancy’s bindery. (She operates a book conservation business.) Nancy notes that when she retires this business, this space will be added to the overall living area in the house.
There is a master bedroom and bathroom with a shower at the west or “cool” end of the house, away from the sun, which the couple wanted for sleeping.
Another room serves as Tom’s office but has also been “value-engineered,” as Tom puts it, to become a guest room. Two couches in this room can be moved together to form a bed when needed.
A bathroom with a deep, streamlined tub adjoins the office/guest room. The largest room in the house is the living room/dining area, which opens onto the kitchen.
The interior design aesthetic throughout is, as the couple describes it, mid-century Scandinavian. The walls are a thick layer of plaster skimcoated over blue board, because the homeowners find plaster more durable, waterproof and aesthetically pleasing than sheetrock. The walls are painted in neutral shades.
A covered walkway between the house and garage makes navigation easy in all seasons and is also designed for wheelchair accessibility.
Most wooden furniture is blond and streamlined, although the rooms are punctuated with color provided by artwork on the walls, area rugs and some painted cabinetry, such as in the kitchen. (Nancy, with her artist’s background, made most of the decisions on color.) Many items of furniture are from Tom and Nancy’s old farmhouse, and a few things have been added from IKEA.
The cabinetry in the kitchen and bathrooms was made by the mill workers from locally harvested wood. The cabinets facing the dining room are maple, and the ones in the kitchen are painted poplar. The kitchen also features a soapstone-topped counter that acts as a divider between the kitchen and dining room, and provides additional seating.
It was important to the homeowners that the kitchen have plentiful natural light, so the windows are four feet high. “We spend most of our waking hours in the kitchen,” Ben says. However, he points out, when you have large windows in a kitchen, you lose cabinet space. To make up for that lost space, there is a “hidden” pantry off the kitchen. And because the kitchen is open to the main living area, the Southworths installed their refrigerator in the pantry as well. Ben says a fridge is not necessarily an attractive visual element. Energy-saving LED lighting is used throughout.
In keeping with the Southworths’ long-term living proposition, the front door of the house is wheelchair accessible, as is the large, open shower in the master bathroom that is designed without a door. Eliminating the door also reduced materials expense and makes for easier bathroom maintenance. Another nod to aging in place, but nice under any circumstances, is a short, level, covered walkway between the door of the mudroom/laundry area of the house and the garage. Ben says that “healthy” houses are not supposed to have attached garages in any event.
Outdoors, Nancy’s raised-bed vegetable garden is steps away from the kitchen. She grows salad greens, kale, garlic, peas, cucumbers, onions, tomatoes and much more. Tom is responsible for growing squash and pumpkins. A screened-in porch and outdoor flagstone patio add outdoor living space when the weather is pleasant.
Living in the house
One of the concerns some people have about net-zero and Passive Houses is that they require too much of a compromise in terms of lifestyle and comfort. The Southworths have not found this to be the case. “Being warm is never a problem,” Nancy says. “Being cool can be. But then we just keep those two doors open [for cross ventilation].”
The constant temperature that is maintained from floor to ceiling and the lack of drafts actually makes this house extra comfortable. For example, if a floor is 6 degrees cooler than the upper part of the room, Ben says, it can make humans feel chilly. “But people can’t discern a difference of 3 degrees or less,” he says.
The resulting home (which was certified as a Passive House) is a success on many levels. In terms of efficiency, it produces on average 4,000 kWh more than it uses on an annual basis. This electricity is returned to the local grid through a program called community net metering.
In terms of livability: “It’s a wonderful house,” Nancy says.
“As soon as the sun comes over the mountains,” Tom says, gesturing to the living room windows, “it lights up like a Disney scene in here.”
“Building our first Passive House was a huge challenge,” Ben says.
“It was new territory,” Nancy says.
Compounding the challenge at times was that family members with different opinions were involved in designing it, but their shared history of working together helped offset that. “We had to change some of the ways that we approach designing and building,” Ben says.
In the end, it was worth it, Tom says. “Everything we do teaches us something.”