Anne Raver / New York Times News Service

KINDERHOOK, N.Y. — The little passive-solar house that the architect Dennis Wedlick designed more than 25 years ago with his life partner, Curt DeVito, was state of the art back then. It has all the whimsical geometry of a Wedlick house: an acute isosceles triangle on top of a pillbox; four round white pillars on the narrow porch; floor-to-ceiling windows for the most effective solar gain.

“The triangular, tall, skinny shape acts like a big chimney, literally pulling the cool air in and letting it escape from the tiny window at the top,” said Wedlick, 53, showing off the house one hot day last month. “I wanted something as small as possible, yet I knew we wanted family to visit. The goal was 800 square feet and three bedrooms. That was the design exercise. So how small could you get the bathroom and kitchen?”

Pretty small, considering they crammed 14 people into the house one Thanksgiving. As DeVito, 52, a tax attorney who loves to cook and garden, recalled: “I cooked the turkey dinner in a galley kitchen in a Sears oven with an electric cooktop.”

The home cost $75,000 to build, and it had all the elements of good passive-solar design. The deep overhang of the roof shades the house in summer, yet allows the lower-angled rays of winter sun in. The windows face north, east and west, with limited exposure to the south, which can overheat a passive-solar house.

“But had I known what I know now,” Wedlick said, “I would have spent all that money on a passive-house renovation. I am still proud of it, but it’s like owning an old house. You forgive it for being inefficient.”

Different types of passive

Wedlick’s recent immersion in passive houses, which are so highly insulated and airtight that they require a small fraction of the energy of a normal house to heat and cool, makes the once-cutting-edge elements in this passive-solar cottage seem hopelessly outdated.

(It might not sound as if there’s much of a difference between “passive solar” and “passive,” but the distinction is important: a passive-solar house collects and stores the sun’s energy, but like any house, it can leak air; a passive house is based on a more advanced system that is not as dependent on the sun, and its super-insulation and structure allow it to hold warmth in winter and keep cool in summer.)

Leaky though it may be, this 1,000-square-foot cottage was what started Wedlick’s career as a green architect. He has since designed some 80 passive-solar houses, ranging in size from 1,000 to 8,000 square feet, and nine passive projects, including two town houses for Habitat for Humanity, a church and an office for a transformer recycling company. In 2012, he changed the name of his firm, Dennis Wedlick Architect, to BarlisWedlick Architects, to acknowledge the many projects he has designed with his longtime architectural partner, Alan Barlis. (The two have put together a monograph of their favorites, “Classic and Modern: Signature Styles,” out this month from Oro Editions.)

Earlier that day, he showed off his Passive House Project, a 1,600-square-foot structure in Claverack, N.Y., with soaring bow-arch beams and a two-story south-facing wall of glass. The first passive house to be certified in New York state (and one of four projects he has had certified), it costs 84 percent less to cool and 99 percent less to heat than a conventional home of the same size, he said. And on a 90-degree day, it was a comfortable 70 degrees indoors, despite that wall of glass, thanks to its compact shape and the 12-inch-thick super-insulated panels that wrap the building.

The house aced its “blow test,” he said, referring to the test administered during construction to measure how much air is leaking in or out. “Ours was five times lower than the minimal airtightness requirement,” he said. “We thought our machine was broken.”

His teacher, Katrin Klingenberg, the German architect who founded the Passive House Institute U.S. in Urbana, Ill., didn’t believe the score, he said, but they took it “again and again, and there was nothing wrong with the machine.”

Like a thermos

Because a passive house is virtually airtight, an energy-recovery ventilation unit exhausts stale air and draws in fresh, exchanging heat in the process: in winter, heat from the exhausted air is transferred to the cold incoming air; in summer, heat and humidity are drawn out of incoming air and transferred to outgoing stale air. “Think of a thermos that keeps something hot or cold as long as possible,” Wedlick said. “A passive house is all about creating an equilibrium.”

Back at the house, DeVito stared out the outdated double-glazed, double-hung floor-to-ceiling windows. He has heard it all before. “We love this house, it’s our home,” he said. (Though the two still maintain an apartment in Battery Park City in Manhattan.)

The meadow was full of mullein, Queen Anne’s lace, clover and phlox. A grove of tall white pines rose off to the left, and there was a pond full of frogs below. But just like the house, this diverse landscape represents a long learning curve.

“When we first came up here, the field was full of sumac and cedars,” DeVito said. “We got some guy with a bush hog to cut it all down.”

What did they know? “We were just two guys from the city,” said Wedlick, who grew up in Secaucus, N.J. “We were planting daffodils in the woods!”