Question: I HAVE A NEW MASONRY FIREPLACE WITH GAS LINE. WHAT TO DO? DO I PURCHASE A COMPLETE UNIT FROM SAY HEAT IN GLOW OR CAN I BUILD A UNIT BY BUYING LOGS, DOORS, ETC IF THIS IS POSSIBLE.PROS AND CONS? COST DIFFERENCES? Answer: Do not build a unit if you are looking for heat. Glass doors cannot be used in the closed position when using regular gas logs. For the best heat and efficiency, purchase a gas fireplace insert and reline the chimney with flexible aluminum piping. An insert is sealed and designed for heat. If you only care about the style..and intend to use for only a few hours a week, simply purchase inexpensive gas logs.