The carbon footprint of new buildings keeps shrinking. But most buildings are old—and heating and cooling them is one of the world’s largest sources of emissions. It isn’t a simple process to retrofit a large building to make it more efficient and get rid of fossil-fueled heat. But one new startup wants to make retrofits easier and cheaper by baking all the changes into a new facade.

The startup, called Hydronic Shell Technologies, designs prefab panels with built-in insulation, heating, cooling, and ventilation aimed at retrofitting old apartment buildings. Because the panels are attached outside, tenants don’t have to move out when the retrofit happens.

Founder David Goldstein started thinking about the idea after New York City passed a law in 2019 requiring large buildings to cut energy use. Goldstein, an engineer, had worked on a project to help a multifamily building decarbonize.

“It really opened my eyes to two huge challenges,” he says. “One was just the economics. To do this kind of retrofit work and get any kind of return on investment was extremely difficult; these projects just didn’t pencil out.” The second problem was the logistical challenge of trying to retrofit a building with people living inside.

Goldstein knew that it was possible to add insulation via a new facade—like wrapping the building in a blanket—and started thinking about how the “blanket” could also be heated. Because most old buildings don’t have insulation in their existing walls, if the facade were heated, the warmth would travel inside.

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