Windows are responsible for approximately 10% of U.S. energy consumption — heat leaking in during summer and out during winter. Billions have been spent on low-emissivity coatings, argon fills, and vacuum gaps. The problem has resisted fundamental improvement because transparent materials generally conduct heat well.
MOCHI (Mesoporous Optically Clear Heat Insulator) is over 90% air by volume, over 99% transparent to visible light, and blocks heat transfer 10 times better than glass. It reflects only 0.2% of visible light.
The mechanism is the Knudsen effect. Polysiloxane tubes form around micelle templates during synthesis, creating pores 2-50 nanometers in diameter. At this scale, the pores are smaller than the mean free path of air molecules — the average distance a molecule travels before colliding with another. Gas molecules inside the pores collide with the walls more often than with each other, suppressing convective and conductive heat transfer through the air. The material doesn't insulate by being something — it insulates by organizing nothing.
The 90% that is air does the insulating. The 10% that is polymer provides the structure that keeps the air organized at the right scale. The best insulator is not a substance but a geometry: emptiness partitioned into compartments too small for its contents to behave normally.