This Sag Harbor home was built as a geodesic dome in the early 1980s. The three-bedroom, two-bathroom house is on the market for $865,000.

“The people who built it originally were into energy conservation,” says listing agent Nadine Campbell of The Corcoran Group. “These homes are very energy efficient.”

advertisement | advertise on newsday

A geodesic dome is a semi-spherical design that was popularized by U.S. inventor Buckminster Fuller in the 1950s. The design has a low surface area per unit of volume, which means less exposure to cold in winter and heat in summer.

The 1,800-square-foot home has an open living area with two bedrooms on the main floor and a loft. The house has a finished basement, which is partially above ground and partially below, and there’s room on the 0.75-acre property to expand the home and add a pool, Campbell says.

“It’s for someone looking for something unique,” Campbell says.