I have a room that I built on the back of my house, it is 14x40 with a divider wall that makes a seperate room 14x14. This wall has a set of 6' 15light french doors in it that can be opened to make it basically one big room. The entire room has 6" insulation in the walls and 7" in the ceiling. The 14x14 room also has 7' in the floor. The small room is going to be a office the other a sun room. What would you suggest for heat? I have a 17,500 btu window air conditioner framed into the wall of the small room that runs on 220v 20amps. So I have that as an option. I also want to be able to heat the big room somewhat. Any suggestions that won't break the bank. Also if it matters I am in the middle Tennessee area. Thanks in advance.