Fireplaces are romantic. Who wouldn't love a fireplace in their living room, family room or even the master bedroom? They help us relax but do you realize how little heat we get from older fireplaces? The average masonry fireplace is inefficient because it draws air from the room when a fire is burning and if you forget to close the damper, you'll also lose warm air that escapes through the chimney.
Like older homes with little or no insulation, older fireplaces were designed when energy prices were much lower than today. With today's focus on green homes and saving energy, maybe it's time for you to research and find ways to increase your fireplace efficiency?
While we focus on how a fireplace looks visually — the hearth, the firebox, the fireplace mantel and surrounding trim, these features don't affect the energy efficiency of your fireplace. The underlying problem is traditional masonry fireplaces heat by radiation which warms objects in a room but not the air. When you recognize that fireplaces pull already warmed air into the fireplace and send more than 90% of the heat generated up the chimney, you start to understand that a fireplace isn't helping you heat your home.
Heat is lost when you forget to close the damper to prevent warm room air from escaping up the chimney. Fires need oxygen (air) to burn and create heat. When older fireplaces pull this air from the room where the fireplace is, there may be a net loss of heat because most of the heated air escapes through the chimney. Fireplaces are complicated so if you want a detailed description, you'll enjoy this Homeowners Guide to Chimneys, Fireplaces and Woodstoves.
Improving Fireplace Efficiency
With more emphasis on energy efficiency, enhancements have been made to the design of traditional fireplaces. These features can be added to your fireplace to improve its operating efficiency. At the high end you can place a fireplace insert inside your firebox or replace your fireplace with a zero clearance, pre-fabricated metal fireplace.
- Outdoor combustion air intakes – bring cold air in from outdoors to provide the oxygen needed by the fire rather than stealing warm air from the room.
- Heat exchangers – pull cool air in at the bottom of the fireplace, heat it and return the warmed air to the room at the top of the firebox. The problem is much of the heated air gets pulled back into the fire.
- Blowers – can be added to most fireplaces to improve overall efficiency and supplement your home's heating system. The blower pushes heated air out into the room versus letting most of it go up the chimney.
- Glass doors – help reduce heat loss when used to control air flow. With a blower that pushes warm air out to the room, you can close the glass doors (check manufacturer specifications as not all doors can handle the intense heat). When you're letting the logs burn out, you can close the doors to prevent heat loss while the ashes cool down.
- Firebacks – sit at the back of the fireplace. They absorb heat from the fire and reflect it back into the room to increase the heat output of the fireplace. They should never be used as an alternative to repairing a damaged firebox.
- Fireplace inserts – are metal boxes that fit inside your firebox. They are much more efficient than an open fireplace so they usually require a stainless steel flue liner.