Scientists create window material that blocks heat without blocking views

The new material, called MOCHI, has a volume of more than 90% air and is made from a silicone gel.

Scientists at the University of Colorado have developed a new transparent insulating material that can drastically reduce heat loss through windows, a long-standing challenge in the design of energy-efficient buildings.

The material, called Optically Transparent Mesoporous Thermal Insulator (MOCHI), is composed mainly of airbut remains strong, durable and almost completely transparent.

The investigation, published December 11 in the journal Science, describes a material that could be manufactured in thin sheets or thicker panelsdesigned to be fixed to the inside of windows. Although MOCHI is still restricted to laboratory production and is not commercially available, researchers believe it has the potential to significantly reduce energy consumption in homes and commercial buildings around the world.

The buildings currently represent around 40% of global energy consumptionmuch of it lost through heating and cooling. Windows are an important weak point because, unlike walls, they have to remain transparent. “Finding transparent insulators is really a challenge,” said Ivan Smalyukh, senior author of the study and professor of physics at CU Boulder.

MOCHI overcomes this challenge by combining optical transparency with strong thermal insulation. The material is based on silicone gel filled with a dense network of microscopic pores, each much smaller than the width of a human hair. These pores are filled with air, which constitutes more than 90% of the total volume of the material. Despite this, MOCHI remains strong and visually transparent, reflecting only around 0.2% of incident light.

Pores are essential to how the material blocks heat. Normally, heat spreads through the air as molecules collide and transfer energy. Inside MOCHI, the pores are so small that the air molecules cannot collide freely. Instead, they repeatedly hit the pore walls, drastically limiting heat transfer. In laboratory demonstrations, a sheet of MOCHI just five millimeters thick was able to block enough heat so that a flame could be placed against it without causing burns on the other side.

MOCHI is often compared to aerogelsanother class of highly effective insulators used by NASA in Mars rovers. However, aerogels often scatter light, which gives them a cloudy appearance. By carefully controlling the size and arrangement of MOCHI’s pores, the CU Boulder team achieved good insulation performance without sacrificing transparency.

In addition to windows, researchers see potential applications in solar heating systems that capture and retain heat for buildings, even on cloudy days. For now, the large-scale production remains a challenge, as the process is slow and complex. Still, the ingredients themselves are relatively cheap, raising hopes that production can be scaled up in the future.