QUESTION: I have a standard furnace in my house, but I would like to add a wood-burning fireplace for more heat and the ambiance. My existing masonry fireplace seems to chill the house. What should I look for? ANSWER: Your open masonry fireplace actually does cool your house.This is because heated indoor air is drawn in the open fireplace and up the chimney. You may feel comfortable in front of the fireplace, but your furnace will run like crazy trying to keep the rest of the house warm.If you really do like the ambiance of an open fireplace, close all the doors to that room, open a window and turn the furnace thermostat way down. You will still lose some heated air up the chimney from the rest of the house, but hopefully much of this air is being drawn in the open window.Every efficient wood-burning fireplace will have tight-sealing glass doors to block the loss of already heated room air. You may be able to operate some models with the glass doors opened and just a screen covering the opening, but I do not recommend burning it this way for very long. When burned properly, the efficiency of a good fireplace can be 70 percent or more.Decide if you want a zero-clearance or masonry fireplace. If your old fireplace is large, you may be able to fit a new masonry one inside of it. If you plan to install a fireplace somewhere else, installing a zero-clearance model is easier. It is designed to be safely placed against wood wall studs.A heating-circulating fireplace is a must for the best efficiency and maximum heated air output. Many of these operate without a fan and rely on the natural flow of room air around the superhot firebox. As the air gets hot, it becomes less dense and naturally flows out into the room through an upper vent. This pulls room cooler air in a lower inlet to be heated.If you want more heat output and better control of the flow of heated air, install an optional blower kit. Each manufacturer offers its own specially designed blower kit to mount on its fireplaces. The better ones have thermostats and variable-speed controls for the best comfort.A blower kit can usually be added by the homeowner after the fireplace is installed.For the greatest efficiency and least drafts, install an outdoor combustion air kit with the fireplace. Make this decision before you install the fireplace because a duct has to run to it to bring in the outdoor air.I set up my wood-burning fireplace as a positive-pressure design. A blower forces outdoor air around the firebox and into my living room.This is slightly less efficient, but it distributes heated air more evenly throughout my house and I like the fresh air.The following companies offer efficient wood-burning fireplaces: Desa International, 866-672-6040, www.desaint.com; Fuego Flame, 800-445-1867, www.fuegoflame.com; Heat-N-Glo, 888-427-3973, www.heatnglo.com; Kozy Heat/Hussong, 800-253-4904, www.kozyheat.com; and Lennox Hearth Products, 800953-6669, www.lennoxhearthproducts.com.James Dulley has a degree in mechanical engineering. His column is published in more than 400 newspapers.