These super-insulating windows are as energy-efficient as walls—and could help save the power grid

As utilities struggle to keep up with surging energy demand, they’re starting to turn to an unexpected tool: windows that insulate like walls.

“Think of it like a thermos bottle in your walls,” says LuxWall CEO and founder Scott Thomsen, who worked in the semiconductor and flat-panel display glass industry before taking on the challenge of windows.

Energy-efficient windows aren’t new. But a radical design from LuxWall, a Michigan-based startup, goes further. Rather than relying on double or triple panes...