NxLite

Nxlite makes a window coating that reflects heat while passing visible light, and unlike every other low-emissivity coating, it doesn't corrode in open air. That sounds like a detail. It's the entire constraint: conventional low-E coatings must be sealed in an argon gap, which is why they only exist inside whole new windows, and why the argon leaking out ends the window's life. Nxlite's coating survives oxygen, so it can go on a thin insert that fits an existing single-pane window, or onto plastic, which no one else can coat at all.

That turns window efficiency from a replacement project into a retrofit. The country has an enormous installed base of single-pane windows, in old housing stock owned by people who will never authorize a full replacement, and they leak heat every winter and take it on every summer. Meeting that building where it is, instead of asking it to become a new one, is what makes the difference reachable.