I have a home with an attached sunroom of approximately 400 sq. feet. I know that it was not included in square footage calculations when I purchased the home. I am having a significant amount of work done on the room including piering the foundation, replacing the roof, replacing the saltillo tiling, refurbishing the cabinet work, interior painting, and replacing the exterior doors and storm doors. It is totally enclosed, althought the roof is not insulated (metal roofing on plywood). It has electricity, and lighting. My question is would this room be counted as interior square footage by the simple addition of a window heating/cooling unit?
What would need to be done to make it count in interior square footage calculations for the purpose of possible resale in the future. Since I am already spending a significant amount of money on this room, if I can increase the square footage of the home, and hence potentially increase the resale value of the home, by simply adding some type of heating and A/C unit, it would make sense to do this.