Chimney safety question

December 2, 2010 9:09 AM

Help me evaluate these claims from a chimney sweep.

This summer, we moved into a newly renovated house in DC. It has a chimney, and this morning we scheduled the local affiliate of a national chimney cleaning company to do a cleaning and inspection.

The cleaner told me that the chimney was clean, so he didn't bother to clean it further. (Yay!) Instead, he did a brief inspection, then tried to get me to pay $1500 to parge coat the brick in the smoke chamber to close cracks that could potentially gather smoke residue (creosote, which is flammable and creates a fire hazard) and install a cap damper. In support of this recommendation, he quoted me an NFPA code about parge coating that (of course) I can't access myself.

The guy told me that it was safe to use the fireplace, but he wrote "Recommend Chimney does not get used" on the receipt, which he explained was just to protect himself from liability. So, do I need to pay to get this fixed? Isn't the whole point to chimney cleaning to remove the buildup of creosote? If I have a flue damper, why do I need a cap damper? (It looks like a superior setup energy-wise, but not a safety issue.)

posted by anotherpanacea to Home & Garden (5 answers total)

Best answer: The parge question is hard to diagnose without knowing how bad the cracks look, and generally how the chimney is constructed. On one hand: if there's no creosote buildup now, and you use well-seasoned wood and burn it hot, and if you have the chimney cleaned annually (or every few years if you don't burn much wood), then there's no reason creosote would accumulate sufficiently to cause a chimney fire. Houses heated primarily with wood in fireplaces and with unparged chimneys have survived for hundreds of years. (Some people used to set a chimney fire deliberately as a cheap way of cleaning the chimney, but don't do that at home.) I've had unparged smoke chambers in every house I ever lived in, burned plenty of wood, and never had a chimney fire.

On the other hand, however, here's a more detailed explanation, including quotes from the NFPA code. Parging does appear to be the current recommendation. It not only prevents creosote accumulation in the cracks and corbeled brick layers, but makes a more easily-cleaned smooth surface as well.

The cap damper is unnecessary IMHO.
posted by beagle at 9:35 AM on December 2, 2010

Response by poster: Thanks beagle! Just what I was looking for.
posted by anotherpanacea at 9:47 AM on December 2, 2010

Just as a point of comparison: my house in Sweden is heated with wood, including warm water and central heating (via an isolated tank that stores the warm water). This means a wood fire twice a day when it's freezing, and once every two days in mid-summer. Government regulations make that the chimney sweep comes four times a year (used to be twice) to prevent creosote built-up getting critical. A check with a video camera of the inside of the chimney is made every two years. The chimney is brick, from the forties, uncoated. He never made any noises about the safety of the thing.
I would have the thing cleaned once or twice a year, and every now and then checked for cracks by someone who can actually show you how it looks (I got to look at a b/w video, straight off the camera, very instructive).
posted by Namlit at 10:11 AM on December 2, 2010

You could also call around the building trades in your area to find a recommendations for a local chimney and get a second opinion. Cracks could be effectively irrelevant if you burn dry wood and clean the chimney regularly; then again, they could be, over time, a problem.
posted by cool breeze at 2:37 PM on December 2, 2010

FWIW:

Beagle correctly says "burn it hot." I burn wood in a wood stove as my main heat source and use a magnetic thermometer to gauge the temperature. We're on our third winter, burning about four cords per cold season, and usually keep the stove between 400 and 550 degrees F while actively burning (that is, not during warm up or letting the fire die down at the end of the night). Annual cleanings by a sweep have not turned up any creosote. Sweep says "Keep doing what you're doing." We *don't* load up the stove at the end of the night and close up the airflow.

YMMV, but I wanted to say a little more about burning hot.
posted by MonkeyToes at 5:24 PM on December 2, 2010