Everything was excellent about the loft except the sub-par air conditioning. To be fair, it would have to be a very strong unit indeed to get around the basic physics of the situation: You are sleeping near the ceiling in a very tall space, and heat rises.

Martina is an excellent host, but if you are visiting at the height of summer, I would definitely go for her nearby Respighi Guest House instead, where the air conditioning situation is perfect. Both are in a great location for exploring the city, especially if you are arriving/departing via Termini.