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, it uses a vacuum to block heat transfer, the same way your Yeti tumbler can keep a drink ice-cold or steaming hot while the outside stays close to room temperature.

Cutting energy bills in half

A typical energy-efficient window might have an R-value (the measure of a material’s resistance to heat transfer) of R3. Luxwall’s windows have a rating of R18, similar to a solid wall. When they’re used to replace single-pane windows, they can cut energy use by as much as 45%.

Some of the startup’s first customers are large building owners, like JPMorgan Chase, looking for ways to slash energy bills. Homeowners are beginning to adopt the windows for the same reason. On large projects, the payback period for the windows can be three to seven years. Now, some utilities, like Con Edison and Eversource, are starting to offer incentives to use LuxWall as they look for new ways to help the power grid.

“When we go in and we retrofit a building from R2 to R18, the amount of kilowatt hours that we’re saving is dramatic,” Thomsen says. “Yes, we save energy efficiency and save costs for the property owner. But we’re realizing our biggest benefit is that we’re keeping electrons on the grid. … When you don’t send electrons to HVAC units, you’re sending electrons to data centers. Our theory is that you can retrofit buildings faster than you can build power plants.”

Making a super-insulating window

The idea of vacuum-insulated glass isn’t new, and first showed up in a lab in the 1960s. But unlike insulated bottles that can be mass-produced in a single size, windows of multiple sizes and shapes are difficult to scale. “In my mind, the reason it had never been successfully commercialized was that you have to really blend material science with advanced manufacturing,” Thomsen says. As the startup developed a feasible manufacturing process, it also got funding from Bill Gates’s Breakthrough Energy Ventures and other VCs to build a factory. The company has raised $167 million to date.

Inside a 217,000-square-foot factory in Litchfield, Michigan, a highly automated production line makes windows in custom sizes. (In one current project, they’re producing windows for a 40-story high-rise in New York City.) Large sheets of clear and low‑emissivity glass are cut, edged, drilled, and tempered. Then they’re carefully joined on a vacuum assembly line, with tiny support pillars and sealants applied using lasers and heat. The air is removed between the panes, creating a vacuum that turns the window into a wall‑like insulator.

Another 276,000-square-foot factory is under development in Detroit. The project previously won a $31.7 million grant from the Department of Energy that was canceled last year in a round of DOE funding cuts; the company is appealing the cancellation while still moving forward with construction. The building is complete, with some equipment on the way, and will be running early next year.

“We’re cranking up the output,” Thomsen says. “So we’re going to really drive better unit economics. The goal is to start replicating this in multiple locations beyond Detroit.”