Long ago, in the era of the grand estates, the riverfront neighborhood in Hyde Park was the “wrong” side of the tracks—mostly because of those tracks themselves and the trains that ran on them, spewing noise and coal smoke.

Not in this century. The tracks carry sleek Amtrak liners, the sounds of their passing a small inconvenience if not an outright part of the neighborhood’s charm. The coal smoke is no more. And the families who’ve built on these riverfront lots feel fortunate indeed. Perhaps it is in part this sense of feeling blessed that leads Bill and Ann Reilly to act and live in ways that will preserve beauty into the future. A cursory glance from the north might lead one to believe their home is just another large (3,200 square feet), handsome dwelling on the Hudson’s eastern shore. Until, that is, one notices the 65 photovoltaic cells on the roof.

Stepping in the front door is like becoming part of a gracious frame around an ever-changing mural of the river. Lots of window space brings the outdoors right in. “This is my dream house that I never thought I’d actually have,” Ann says, quietly exultant. “If anything bothers me, I just go outside and let the river make it better.”

Bill grins. This may not be the first time that the builder/husband has heard this particular “attaboy,” but one senses he’ll never tire of it. If the three-year-old home is the house Ann has always wanted to live in, it doesn’t take long to get the idea that it’s also the house Bill always wanted to build.

Ann leads the tour of the main floor. Daylighting, in the form of 24-inch diameter solar tubes, is used throughout the home; the Reillys almost never touch a light switch in the daytime. “Some days the photovoltaics produce 50 kilowatts of electricity, and we only use 10 or 12,” says Bill. “If you go look right now, the meter’s probably going backwards.”

Bill’s business, Reilly Homes, was incorporated in 1965. “I built houses all over Dutchess and Putnam counties,” he says. “My son took over 10 years ago. We waited and watched while this lot went through the approval process; we had our eye on it for a while. You should have seen it—we had to bring in two rock hammer excavators for two days to dig a foundation. It was all stone.”

Tamed, the fieldstone is a handsome feature of the building’s exterior. And in the basement, the house reveals its true individuality in more ways than one. There’s a commodious rec room with a ping-pong table—ideal for the host of grandchildren whose pictures are proudly framed on the upstairs wall. “When everybody’s here, we have just enough bedrooms,” Ann says happily.

Beside the stacks of totes that contain Ann’s Christmas décor, a sample of the material that forms the dwelling’s exterior walls is casually displayed. It seems likely that most who visit this home receive an education in green building from the mouth of one who’s done it with his own two hands; Bill could recite the considerable virtues of his Reward Walls in his sleep.

The forms that create the insulating concrete form (ICF) wall system are made of two panels of expanded polystyrene (EPS) held together by embedded plastic ties. Each block weighs only seven pounds without the concrete filling, and the edges are cleverly notched to interlock. “A kid could manage this stuff,” Reilly says. “You end up with an R factor of 32, maybe 34…It makes a wall a foot thick. It’s waterproof, fireproof, pest proof, and can withstand a 225-mile-per-hour tornado.”

Reilly says the ICF concept has been around since the 1970s, yet he does not personally know of any other residence that features them. “The main thing is builders are still unfamiliar with this. But they’ve been improving on it to where it’s very compatible with standard construction,” he says. “I’d say it added only about a dollar a square foot to building costs—and no tree-killing involved. None.”

The geothermal Climate Master furnace is an open-loop system, pumping water in and out, and works in tandem with the Lifebreath heat recovery ventilator, which in the Reilly home is literally the breath of life. “This house is so tight that without a ventilation system, we’d literally suffocate without opening the windows,” Reilly says. “The air quality in the house is measurably better than the air outside.”

The geothermal system and the photovoltaic cells, Reilly explains, added the most to the house’s price tag—but he urges interested builders and customers to explore the reality of these options with their financiers. “Say you want to build a $300,000 house, and adding these features would make it a $350,000 house,” he says. “A smart lender might look at the savings you’ll get on utilities and realize that you’ll be able to carry the higher mortgage because of that.”

And smart builders and buyers might find themselves one day aspiring to creations like this: a marriage of ultramodern energy efficiency and cozy elegance, a house created with love that transcends any single family or any one moment in time.