On March 16, the Nature website published the technical progress of "Highly transparent cellulose airgel research and thermal insulation application for door and window glass" of the School of Physics, University of Colorado.

To maintain a comfortable indoor environment, buildings consume 40% of the world's energy. Windows and skylights are the least efficient part of a building envelope in terms of passively insulating the building interior from the cold or hot outside, as simultaneously achieving high transparency and glass insulation remains a challenge. Here, a University of Colorado research team demonstrates highly transparent aerogels made of Earth-abundant biopolymer cellulose, utilizing methods such as colloidal self-assembly and compatibility with roll-to-roll processing. The airgel has a visible light transmittance of 97-99% (better than glass), a haze of ~1%, and a lower thermal conductivity than still air. These lightweight materials can be used as multi-layer insulating glass interlayers, or they can be used to retrofit existing windows. The research paper shows how aerogels improve energy efficiency and may offer advanced technical solutions for insulating glass units, skylights, daylighting and façade glazing.

To provide ideal indoor conditions, indoor-outdoor energy exchange needs to be minimized through heat conduction, convection, and emissions with little or no additional energy supply. Achieving this with glass is especially challenging. While current solutions to this challenge utilize insulating glass units (igu) with air or gas fill, the high thermal barrier properties of such igu require large gap thicknesses between glass panes, which in turn are affected by gas convection, window Number of grids and structural constraints. On the other hand, the use of thinner vacuum insulating glass units is limited by hermetic integrity and high cost. Low-emissivity silver and other coatings can limit energy loss from black-body-like electromagnetic emissions from inside room-temperature buildings, and while these methods can moderate the temperature difference between indoors and outdoors to some extent, they come at the expense of transparency in the visible range.

Aerogels, a highly insulating material with applications ranging from pipe insulation to Mars rovers, have been sought after as solid replacements for gas fillers within igus because they are a class of materials capable of outperforming still air and other gases Efficient thermal barrier material for fillers. However, aerogels are often mechanically fragile and strongly scatter light. Fabricating aerogels with low haze, high transparency, and mechanical robustness at the scale and cost associated with architecture also remains a challenge. The development of transparent aerogels, including cellulose aerogels, is still limited to small scales while still not being sufficiently haze and transparent for use on most types of glass.