Windows?

[Limesy]

I've been told there are windows/glass blocks available in the game but haven't been able to research them yet? Seems a little strange that I can make glass already but can't research how to make a window. Is it locked behind other research?
Send help - my village needs windows!
http://steamcommunity.com/sharedfiles/filedetails/?id=1088186893

[Disjointed Sky]

You need to research basic glassblowing, should come up on the research station when you complete other research goals