Using fireplaces efficiently
Q: We like to use our brick open wood-burning fireplace, but it makes the rest of the house cold. Our heating bills are high enough, so what simple things can we do to make the fireplace more efficient?
A: During the winter, a warm fire can be quite comfortable. Radiant heat from the flames and coals keeps you warm when you are sitting directly in front of an open fireplace. But unfortunately, most fireplaces lose more heat than they produce.
That warm, relaxing open fire is actually costing you a lot of money – in several ways. First, for some, firewood must be purchased, which is not cheap. Second, the radiant heat feels nice in front of the fire, but already-heated air is being sucked up the chimney from the rest of your house. This makes your heat pump or furnace run longer. Third, if there is no damper on the fireplace or the fireplace is not fitted with its own outdoor air source, indoor air is escaping up the chimney when the fireplace is not in use.
The best tip is to avoid using the fireplace in extremely cold weather. All of the indoor air lost up the chimney is being drawn outdoors through leaks in the house exterior. During milder weather, the air leaking indoors is not as cold so less energy is needed to warm up this cold air.
It also helps to crack open a window at little in the room by the fireplace and close doors leading to the room. Much of the excess air being drawn up the chimney will be cold outdoor air from the open window. When sitting right in front of the hot fire, you probably will not notice the chilly breeze.
Do not place wood into the fire several hours before bedtime so the fire is totally out by the time you go to sleep. It is not safe to leave a smoldering fire. Also, if the fire is completely out, you can close the chimney damper to block room air loss without filling the room with smoke.
High-quality doors are worth the expense
If you make just one investment to improve the efficiency of your fireplace, it should be to install high-quality glass doors. These doors control the amount of indoor air that escapes up the chimney when a fire is burning and also when one is not.
High-quality fireplace doors are not cheap, but they are worth the expense. The best doors are relatively airtight when closed. By adjusting combustion air vents in the bottom of the glass door frame, you can still have a raging fire without major indoor air loss.
Keep in mind, the fire does need an adequate supply of combustion air for an efficient, clean burn. If the air flow is reduced too much, creosote buildup occurs, leaving the potential for a chimney fire. I recommend having the chimney inspected and regularly using several squirts of a creosote control spray during each fire.
Burn only well-seasoned wood or no more than one unseasoned log to three seasoned ones. If you try to burn more unseasoned wood, it requires more combustion air to keep it burning well, which draws even more air out of your home.
There are several designs of heat-circulating grates that increase the heat output from a fireplace. Many efficient grates are designed to fit snugly under the bottom edge of the fireplace doors and contain an electric blower that circulates indoor air through the grate, keeping the air warm.
Stoll Fireplaces makes a unique heat exchanger, which mounts at the top of the fireplace opening, creating a tremendous amount of heat output. These models work with gas or wood-burning fireplaces.
A circulating heat exchanger with built-in glass doors is also available for a more airtight combination. Also, an optional upper oven section is available for cooking and baking, which can help reduce energy use.
When your fireplace is not in use, insert an inflatable chimney pillow or balloon in the fireplace flue. This seals much better than the chimney damper. Once the pillow is inflated, it should stay in place. Some models include a pole to keep it steady. Chimney top dampers, which operate from indoors with a chain, also help reduce air leakage and keep critters and debris out of the chimney. It’s a good idea to hang a sign or ribbon in the fireplace to indicate that the damper is shut or a pillow is installed. This will hopefully stop someone from building a fire when the chimney is closed.
For additional tips and information about fireplace efficiency, check out TogetherWeSave.com’s Home Efficiency Analysis Tool (http://homeefficiency.togetherwesave.com).
The following companies offer fireplace efficiency products: Battic Door, 508-320-9082, www.batticdoor.com; Diamond W Products, 248-652-8833, www.diamond-w.com; Northline Express, 866-667-8454, www.northlineexpress.com; SaverSystems, 800-860-6327, www.homesafetyproducts.biz; and Stoll Fireplace Inc., 800-421-0771, www.stollfireplaceinc.com.
Send your questions to: James Dulley
6906 Royalgreen Dr.
Cincinnati, OH 45244
You can also reach Dulley online at: www.dulley.com
James Dulley is a nationally syndicated engineering consultant based in Cincinnati.