We had a ventless gas log set installed in our rowhouse fireplace. It is the best improvement we’ve done so far. With a ventless log set, almost all of the generated heat stays in the house (w/vented it goes up the chimney). it heats our whole first and second floor, and our winter gas bills are lower. this was a happy, unintended consequence. The gas log people can tell you, based on the size of the room and firebox which way to go, but we’re really happy with ventless. We used Cyprus Air in Alexandria. They were just okay – great in the showroom, but slooooow with the actual install part. the permitting process is time-consuming and expensive. the sooner you get it done, the quicker it will be – Nov/Dec is high season for fireplace installation.