Heating, ventilation, and air conditioning of buildings account for about 15% of the global energy consumption, but about 20% of this building-related energy is lost because of inefficient windows. Greenhouse emissions associated with producing and using this energy contribute substantially to climate change. Is there a solution to this challenging problem? Starting from the physical principles associated with energy loss through windows, we will describe our development of visibly transparent, infrared-reflecting, thermally super-insulating materials that may replace or retrofit the inefficient windowpanes of residential and commercial buildings. Using many demonstrations, we will discuss how production of such unusual transparent aerogels is aided by bacteria, with the source materials in the forms of waste of food industry and beer wort, to make such smart windows highly affordable.