Energy-saving windows play a crucial role in sustainable development of green buildings. Integrating super-insulating aerogels with glasses is an attractive method to minimize the energy loss through building windows. However, achieving energy-saving windows with high transparency, super insulation, mechanical robustness, low cost, and scalable aerogels remains a challenge. In a recent study published in Nature Energy, Smalyukh and coworkers synthesized a highly transparent silanized cellulose aerogel for energy-saving windows, overcoming the challenges. This work promotes the practical application of aerogel-based glazing and provides an effective way to save energy of buildings.