First off - I would like to thank everyone for the contributions to this website. The amount of valuable information here is amazing. I am building a new house in WI. I have decided to build a "3 season" room on the house. I am building this room fairly rustic looking and love the look of a roaring fire in the fall. I have three options for the fireplace and would like some feed back from people with experience. The room is not going to be heated or have a/c and its only attachted to the house via a breezeway. The fireplace options are either build a full masonry fireplace, do a masonary "like" fireplace such as "firerock" or do a fireplace box. I am leaning towards the fireplace box - but now I am being told that it will rust out if exposed to any elements. The room will be enclosed so rain will not get on it but if I dont have the windows closed we could get moisture from dew or fog. Can these boxes actually rust? Any advice or suggestions would be greatly appreciated.