According to How the Other Half Lives where did the only fresh air for tenement rooms come from

What was the room called where books were copied by hand?

The room where books were copied was called the scriptorium. According to the article linked below, specific rooms permanently established for copying books were rare. The scriptorium was more usually simply a place conveniently located where scribes could make copies, such as a place where people could sit by windows. A specific room remained a scriptorium only when large numbers of books had to be copied, and once that job was done, copying was likely to be done in any convenient place with good light.