Good news! Possibly a breakthrough!
Over the past several decades many approaches have been tried to make windows better in terms of insulation from heat and cold with less than effective results.
"... So, a team started from scratch, designing a new class of metamaterials built from interconnected nanoscale polysiloxane tubes. Because structural features of the material—including the diameter of the nanotubes and sizes of the pores between them—were all smaller than the wavelength of visible light, the materials let through 99% of sunlight, the researchers reported in Science. The materials could be manufactured at a range of useful sizes and shapes and insulated on par with or better than double-paned glass.
Since windows leak nearly half of a building’s heating and cooling energy, these next-generation windows have the potential for energy, cost, and climate savings. The materials could even trap infrared light, raising their potential for passive, energy-generating windows that use solar energy. ..."
"Physicists ... have designed a new material for insulating windows that could improve the energy efficiency of buildings worldwide—and it works a bit like a high-tech version of Bubble Wrap.
The team’s material, called Mesoporous Optically Clear Heat Insulator, or MOCHI, comes in large slabs or thin sheets that can be applied to the inside of any window. So far, the team only makes the material in the lab, and it’s not available for consumers. But the researchers say MOCHI is long-lasting and is almost completely transparent.
That means it won’t disrupt your view, unlike many insulating materials on the market today, ..."
From the abstract of the Perspective:
"Windows are among the least energy-efficient components of a building. They occupy a small fraction of the exterior but leak nearly half of the heating and cooling energy from the interior.
Conventional solutions such as double glazing and low-emissivity coatings are mechanically robust and optically transparent, yet their thermal insulation performance is limited.
Modern technologies such as silica and cellulose aerogels (a porous material filled with gas) could achieve better heat insulation. However, their optical haze, fragility, and limited scalability continue to hinder widespread adoption.
[Researchers] ... report an optically transparent heat insulator that is built from self-assembled polysiloxane nanotube networks. The material transmits >99% of visible light while conducting heat more poorly than the surrounding still air. This could be used to make clear windows with thermal insulation that is comparable with that of building walls."
From the editor's summary and abstract:
"Editor’s summary
Networks of mesoporous polysiloxane tubes that are optically transparent can be used as highly thermally insulating window coatings. Bhardwaj et al. solvent-exchanged polysiloxane hydrogels with ethanol and then replaced ethanol with carbon dioxide through supercritical drying to create highly porous, graph-like networks of thin, bicontinuous tubes ... The resulting films have greater than 99% visible-range optical transparency and low thermal conductivity and can be used in new and existing windows. ...
Abstract
Mesoporous materials exhibit highly controlled nanoscale structures, often templated by liquid crystalline assemblies of surfactants, with emergent and often designable physical properties. However, scaling their fabrication to be suitable for uses such as envelopes of buildings is challenging.
In this work, we describe fabrication of flexible square-meter-sized films and multicentimeter-thick slabs made of three-dimensional spatial graphs of mesopore tubes that have all structural features under 50 nanometers.
A solution-based kinetic fabrication process templates growing networks of cylindrical surfactant micelles with thin tubes of polysiloxane-forming gel networks and, upon replacing surfactants and solvents with air, yields lightweight materials with greater than 99% visible-range optical transparency and approximately 10 milliwatts per kelvin per meter thermal conductivity. Such predesigned metamaterials enable transparent thermal barriers for wall-grade insulated glass units, square-meter window retrofits, and unconcentrated solar thermal energy harnessing."
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