Indow is a cleantech company in Portland, Oregon dedicated to making the built environment more energy efficient while preserving historic windows. It makes custom interior window inserts for residential and commercial spaces that help original old-growth wood windows perform like new double-panes without altering the exterior of the buildings. This is one reason preservationists turn to them: they do not interfere with historic district requirements that windows retain their original appearance and character.

Historic properties across the United States have them from a 1756 house in New Hampshire with all its original windows to Case Study House #26 in the Bay Area, an iconic American home commissioned by Art & Architecture magazine, to a county government building in Arlington, Virginia that was converted into a homeless shelter.

When buildings settle, the windows settle with them, making them out of square. Indow acrylic window inserts are handmade for each window opening using precise laser measurements. Each insert is edged in silicone compression tube and simply presses into place without a damaging track or magnetic system. The inserts not only make buildings more energy efficient, they reduce the number of irreplaceable old growth wood windows thrown into landfills during window replacement.