More heat from less wood

Q: We had a fireplace installed in our basement a couple of years ago with the aim of warming the place up. It's now colder than ever down there when the fireplace is not used, and it doesn't warm up much even when it’s burning. The fireplace is outfitted with a heatilator that’s supposed to transfer more warmth to the room, but it doesn’t help. We plan to install a woodstove-type insert to boost efficiency, but aren’t sure if routing an outside source of combustion air into the unit is worth the trouble. Very few units that can be installed into our existing fireplace are designed to accept outside air.

A: An outside source of combustion air for woodburning appliances does two good things. First, it boosts household efficiency by eliminating the suction of cold, wintertime air back into your house through cracks around doors and windows to make up for air that goes up the chimney. Outdoor combustion air also reduces the chance of creating negative pressure within the house, which could cause backdrafting of other combustion appliances, creating a carbon monoxide hazard. Most existing woodstoves and inserts aren't hooked up to outside air, and though they work fine, the arrangement is less than ideal. So, what should you do? The first thing is to check with your building inspector. Outside combustion air may be a requirement of new woodburning appliances in your area. If installation of this feature is optional, ask yourself these questions. Was your house built during the last 10 years, using modern windows and doors? Does condensation build up inside windows during winter? If yes, then your house is probably sealed tightly, and an outside source of combustion air is a worthwhile option. On the other hand, if your house is dry in the winter (indicating lots of air leaks) , and you don't mind opening a basement window a bit while a fire is burning, then you may be able to save some work. Either way, install a carbon monoxide detector near the fireplace, just to be sure.