How to convince my dad to let me have the room downstairs?

I'm 16 years old. And for the summer i'm going to have to be staying at my dads more often opposed to my moms, (Since my mom is on the outskirts of town and my dad is more in town). My bedroom is upstairs, and i hate it because our house is noisy, and im a quiet keep to myself kind of person, my room upstairs is fancy and it has hardwood floors and all that crap. But the bedroom downstairs is simple, it fits a bed, a dresser, it has carpet floors, and wood paneling walls. I asked my dad for the downstairs room, but he said no because it's "illegal", since it does not have a bedroom, in case of a fire.. I'd really like the bedroom downstairs, so i can put up some of my pictures without it looking silly, and designing it myself for a cheap price since it's small. How should i convince my dad?