Transparent wood could be used for windows. The material retains more heat than double glazing, but cannot yet be made entirely see-through
Source: https://www.newscientist.com/article/2198126-windows-made-of-transparent-wood-could-help-keep-buildings-warm/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home