Replacing millions of porous windows with energy-efficient versions in older buildings and homes can be prohibitively expensive. Berkeley Lab’s Raymond Weitekamp, a Caltech PhD, has a new approach: an inexpensive, paint-on, energy-efficient coating that can be applied simply and evenly without the help of a professional—while the windows are still in place. Series: "Science at the Theater" [Science] [Show ID: 31938]