A wood stove insert serves several purposes. First of all, they can keep heat from escaping through the fireplace. Wood stove inserts also raise the heating efficiency of the fireplace, allowing it to spread more heat to a wider area. Fireplaces with wood stove inserts are cleaner and easier to manage than open fireplaces.Wood stove inserts fit mostly inside of the fireplace. They consist of a shell that lines the inside of the fireplace and a glass door that can close the fireplace as well. Woo.