November 2011 Energy Solutions

Step-in-time for fireplace safety

by James Dulley
Engineering Consultant

Professional inspection and regular maintenance can prevent chimney fires

Q: I use my masonry fireplace often during winter for zone warmth and the ambiance it provides, but the draft seems to be getting weaker. What chimney problems should I look for when I inspect it, and how can I reduce creosote?

A: Tens of thousands of chimney fires occur every year due to creosote buildup and other problems with chimneys. In many cases, the entire house ends up burning down; lives are lost. These thousands of chimney fires result in as much as $200 million in property losses each year.

Since you have noticed reduced draft up the chimney, schedule an appointment with a professional chimney cleaner. If you are lucky as I was when my fireplace demonstrated the same draft problems, the screening in the chimney cap was just clogged with soot. This blocked the air flow up the chimney. Just tapping the screening with a rubber mallet was enough to knock the soot loose. I later replaced the chimney cap with one with a more open mesh.

If you are not as lucky, there may have already been a creosote fire inside your chimney. The heat from the fire can cause the tile liner to crack and fall from the masonry wall. When this happens, the broken tile may restrict the air flow up the chimney reducing the draft. You should able to see a broken loose tile when looking down the chimney with a bright light.

A chimney fire can also cause the creosote to puff up. It expands and feels somewhat like plastic cooler foam. If you can run a brush down the chimney, some of this puffed creosote may fall down into the firebox. If you find either a broken tile or puffed creosote, your chimney will definitely need a professional cleaning and inspection with a camera.

If repairs are needed, get estimates from several chimney maintenance companies. In my own case, one chimney company found puffed creosote and claimed the tiles were also loose. It gave me a quote of $7,000 to repair my chimney. Another company cleaned and inspected the chimney with a camera, but found no broken tiles. For $200 total, it also sealed the chimney crown and my fireplace has worked fine for years now.

There are some things you can do to reduce creosote buildup. First, use well-seasoned wood and do not try to choke off the combustion air too much to extend the burn time.

Special fireplace logs are available which contain chemicals to reduce creosote formation in the chimney. Using these periodically can help keep the chimney clean. SaverSystems, 800-860-6327, www.saversystems.com, offers a spray to use on regular wood logs and other cleaners to minimize creosote. I now use this spray.

You can clean the chimney yourself on occasion if you do not mind getting a little dirty. This does not, however, eliminate the need for a professional inspection. A local chimney supply store should carry a brush to fit your chimney.

Always wear a high-quality breathing mask so you do not inhale the fine dust particles. Seal the fireplace opening into the room with plastic film and duct tape. Also, put a large drop cloth on the floor in front of the hearth. No matter how well you try to seal it, some black dust seems to always get through.

Go up on the roof and run the chimney brush up and down many times. Wear a safety harness and tie yourself to the chimney when on the roof and always have someone nearby to call for help if needed. It might be overkill, but I always wear my bicycle helmet and a mountain climbing harness so I can lower myself down slowly if I lose my footing.

Much of the hazardous damage to chimneys is caused by moisture entering from outside. This moisture can migrate through the brick and the mortar joints into the chimney. This is bad everywhere, but particularly so in cold climates with a repeated freeze/thaw cycles during winter. Use a water- or solvent-based sealer on the chimney bricks and mortar.

The crown of the chimney is another location for moisture to enter. Tap on it lightly with a hammer to locate any loose areas and brush them away. If the crown is still in good condition, coat it with a special elastomer crown repair compound. If you have a problem during winter, SaverSystems offers a special crown sealer that cures below freezing temperatures.

Check the condition of the mortar joints. Where you find loose mortar, fill in the gaps with a elastomer concrete-colored sealer. Also, inspect the flashing where the chimney meets the roof. Deteriorated areas can be sealed with a flexible flashing repair compound.

James Dulley is a nationally syndicated engineering consultant based in Cincinnati.
If you have a question about energy use or energy-efficient products, send it to: James Dulley, Electric Consumer, 6906 Royalgreen Drive, Cincinnati, OH 45244; or visit www.dulley.com.

For more information

The National Chimney Sweep Guild is located in Indiana. To find a member sweep in your area, contact the guild at 317-837-1500; 2155 Commercial Drive, Plainfield, IN 46168; or visit the guild’s website and click on “Homeowner Resources” at www.ncsg.org.

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