Mr. Landau was also well acquainted with the growing number of “green” building certifications and rating systems in the United States, including popular ones like the federal government’s Energy Star for Homes program and the LEED rating system, for Leadership in Energy and Environmental Design, from the United States Green Building Council.

The goals of these various systems vary widely. Some, like LEED, award points for a variety of environmentally friendly features, like using sustainable construction materials, in addition to energy efficiency. Others, like Energy Star, focus squarely on energy use.

But the most common green building standards, Mr. Landau said, fell short of his ambitions  which included avoiding any on-site use of fossil fuels. “I remember reading a book about someone in England in the 1980s who built a superinsulated house that was only heated by the body heat of the occupants and maybe a tea kettle,” Mr. Landau recalls. “I thought to myself, ‘Why can’t we build our houses that way?’ ”

Energy Star and LEED aim for efficiency improvements of at least 15 percent over conventional construction  and both programs can earn a variety of tax credits and other incentives. The passive-home standard, perhaps because it’s unfamiliar to many officials who create efficiency stimulus programs, is eligible for few direct government subsidies, despite the fact that homes using it can be up to 80 percent more energy-efficient, over all, than standard new houses and consume just 10 percent of the heating and cooling energy.

Add photovoltaic solar panels or other energy harvesting systems, and passive homes can quickly become zero-energy-use homes  or even power generators that can feed electricity back to the grid, according to Katrin Klingenberg, the director of the Passive House Institute-U.S. in Urbana, Ill.

Of course, quantifying the overall energy efficiency of any building is a somewhat imprecise affair. A family living in a well-insulated, highly-efficient home, for example, might keep the lights on all day and the thermostat at 85 degrees in the winter. The occupants of a drafty New England farmhouse, meanwhile, might be energy misers by habit, favoring blankets and sweaters over dialing up the heat.

And while many people are interested in passive homes for their cold-weather benefits, researchers in both Europe and the United States are looking into more applications for warmer climates, using a different balance of insulation, window technology and air control to achieve similar efficiencies.