There's plenty of room outside our sunny south-facing living room in Madison, Wisconsin, to add a sunroom of about 6 x 14 feet. I'd like 4 x 6' well-insulated windows all along the 14-foot south side, and well insulated walls and ceiling. If left open onto the existing living room year 'round, do sunrooms like this increae, decrease, or not affect utility bills?
Claudia ~ Madison, Wisconsin
Claudia, if you don;t want your new sunroom to increase your energy bill, then it is probably best if you have the option to close off the new room from the rest of your home. Although the large windows and the southern exposure will certainly produce lots of radiant heat on sunny days, I can imagine some cold Wisconsin nights which might leave the sunroom a little chilly. Remember, even a well insulated sunroom is going to cool down during the night unless some sort of heat is available, and if not, the cooler room will draw heat away from the conditioned portion of your home. Of course, if you have the option to close off the room at night, then you will be able to control the inflow and outflow of heat, to and from the rest of your home.
You may want to consider installing a sliding glass door between your sunroom and the rest of your house, this way you can enjoy an open sunroom during the day and close it off at night. The sliding glass doors would also allow light to come into your home even when the door is closed, and visually the room would still appear to be open. If you want to see some savings on your energy bill, then you should use the glass doors as the "thermostat" for your sunroom, opening them to allow the collected solar heat into the house and closing the doors to keep heat from leaving your home. Good luck with your project and enjoy the new sunroom!