Building code for 3(three) Season Room

[Matt Fitzgerald]

Hi, can anyone point me to the Massachusetts (Boston specifically) building code for 3-season rooms?  What I'm looking for specifically is: 

• What defines a three season room?
• What crosses the line of making a three season room into additional living space?
• Can three season rooms have electricity?
• Can three season rooms have a heating source, like a gas fireplace?

I'm in the process of redoing an existing 3 season room attached to my house and the inspector told me if I had a gas fireplace, it needs to be converted to living space.  I'd like to find out more information on this requirement.  Why can't I add a heating source to a 3 season room?  

Thanks for any and all insight. 

-Matt