Buildings worldwide consume approximately 40 percent of total world energy, while this consumption directly contributes to greenhouse gas emissions and deepening climate change. Reducing this energy intensity is key to achieving global commitments, especially for the European Union (EU) and Slovakia's goal of achieving carbon neutrality by 2050.

Windows have traditionally been considered the „Achilles heel“ of energy-efficient buildings. While walls can be easily insulated, glass panes must let in light, leading to huge energy losses as they let in heat in the winter and overheat the interior in the summer.

A solution to this dilemma is offered by a team of researchers from the University of Colorado Boulder, who have developed new transparent insulating material called MOCHI (Mesoporous Optically Clear Heat Insulator). This silicone-based gel material acts as a top-notch insulating layer, yet remains almost invisible.

Transparent insulation for zero-emission buildings

MOCHI can be applied as sheets or thin films to the inside of existing windows. A layer as thin as 5 millimeters is effective enough to dramatically slow heat flow. The researchers said that windows filled with MOCHI achieve insulation levels that are comparable or even better than well-insulated walls.

The basis of this innovative material is its unique nanometer structure. More than 90 percent of the material's volume is trapped air. Heat is transferred through gases by collisions of molecules, but the pores in MOCHI are so small (nanoscopic channels) that gas molecules collide with the pore walls more often than with each other, which suppresses heat flow and dramatically reduces their ability to transfer energy. Despite being a highly efficient insulator, the material remains almost perfectly transparent, reflecting only about 0.2 percent of incident light.

Contribution to reducing CO₂ emissions

The widespread implementation of MOCHI technology can fundamentally change the „energy math“ in buildings. By replacing energy-inefficient windows with those coated with MOCHI film, the heating load in winter is reduced and the cooling load in summer is relieved, leading to decrease in energy consumption and reduction of emissions. Given that buildings represent the area with the greatest potential for reducing greenhouse gas emissions, such transparent insulation is an important tool to help architects design buildings that meet stringent requirements for zero-emission buildings (ZEB), which is the new construction standard from 2030.

Estimated CO₂ emissions from state buildings alone in Slovakia reach 187 thousand tons per year, which underlines the urgent need for energy efficiency. Reducing energy consumption has a direct and long-term impact on reducing CO₂ emissions and operating costs.

In addition to passive insulation, researchers also see potential for MOCHI in passive solar devices. The material transmits visible light but retains long-wave thermal radiation, allowing it to capture solar energy for heating water and the interior of buildings even on cloudy days. Such integration of passive solar collection into building envelopes is fully in line with the EU's commitment to increase the share of renewable energy sources (RES) in buildings.

Although MOCHI is still a laboratory product and requires optimization of the manufacturing process, its components are common and relatively inexpensive. Once production becomes more efficient, this transparent insulating material could make a significant contribution to global reduction of energy losses and fulfilling Slovakia's and the EU's commitments in the field of climate and energy efficiency. JRi