I can hardly believe it. When I first came up with the idea to forgo a furnace in favor of a natural gas fireplace to heat our house, I thought no one would let me do it.
Truthfully, if I hadn’t found this one specific fireplace insert that is much more efficient than all the others, I would have dropped the whole idea by now and we’d be choosing which furnace to have installed in the crawl space under our house. That would have been a pain; when a furnace installer-turned-salesman came to give an estimate on the job, he realized that getting the furnace into the crawl space would require cutting out a piece of the opening to the crawl space and then repairing it afterward. And that was the better option between that and cutting a hole in the floor somewhere and having to repair joists.
In general, vented natural gas fireplaces are considered fairly efficient at over 70% AFUE, but this means you’re wasting up to 30% of your fuel! There are unvented ones that can be almost 100% efficient, but you cannot use them as a primary heat source because they can deplete oxygen in the room and create problems with condensation. Not many heating companies in our area carry the Mantis, but I found one. No reports on Angie’s List, but AL customer service looked up their BBB rating - A. The company says they can install it or they can sell it to us and we install it. We’ll get estimates and decide how to proceed. I’ve seen Richard install one on Ask This Old House, and I’ve already read the installation manual for the Mantis, so I think we probably could do it ourselves if we want to. Some online suppliers are selling it too, but I’d want to make sure it’s all legit with warranties and whatnot.
My confidence is growing: now Matt, Robert, our real estate agent, our home inspector, the furnace salesman (who will be losing some business if we go ahead), and of course the fireplace salesman all think it’s a good idea!
We have to make sure the heat is distributed evenly throughout the house (a friend mentioned this as a problem, and our real estate agent was also concerned about that). Not to fear; we have a plan for that too. The fireplace is located near the center of the house, and the existing furnace is right next to it. This is excellent because it means we can use the existing ductwork. When the furnace guy was here, he said if we got a furnace we should put the air intake right next to the fireplace and leave the furnace blower on 24-7 so that the heat from the fireplace would be distributed to every room through the ducts even when the furnace is not firing. Well, that’s essentially what we’re going to do, but the blower will be stand-alone, not part of a furnace that is rarely used. We would also like to integrate the air intake into either the hearth or the mantle/surround, instead of just being on the floor near the fireplace. We need to talk to some HVAC people and see what options we have to do this.