The heating, cooling and lighting of buildings now consumes one-quarter of the world's energy, but passive solar design in new buildings could cut that amount 25 percent by the turn of the century, the Worldwatch Institute research group reported yesterday.

Passive solar architecture puts windows and over-hangs on the south side of buildings to catch the sun in winter and shade them in summer, said Christopher Flavin in his study, "Energy and Architecture: The Solar and Conservation Potential." Structures that rely on the sun and natural cooling breezes still need conventional heating but use 75 percent less fuel than regular buildings, as well as having a lower long-run cost, he said.

"Even large commercial structures will soon be designed to use less than half as much fuel as they do today," Flavin's report continued. Construction of passive solar homes is "a booming new field," he said, but still could use federal subsidies of the kind long given to conventional energy development.

Flavin said that 80 percent of existing structures will still be in use in the year 2000 and recommended neighborhood "house doctors" to advise owners on energy-related improvements. In cold, cloudy climates, architects are designing "super-insulated, very tightly constructed houses with relatively few windows . . . called 'zero-energy' houses," he said, because they require conventional heating only on the coldest days.