To stop chimney odor, reverse the downdraft

Q. We have installed a wood-burning stove, which is tightly sealed to the clay tile flue. About 10 years ago, after heavy rains, we noticed a creosote odor around the stove. The flue and connections are clean, but the odor persists. Do you know where the odor is coming from? Could it be the cap?

— JIM SUOJANEN, MEDFIELD JIM SUOJANEN, Medfield

Q. We use our living room wood-burning fireplace only a few times every winter and we had it cleaned seven or eight years ago. In the last few years, when it rains or is very humid we get a smoke and ash smell from the fireplace. It’s bad. We do have a damper and we also have glass doors on the fireplace. Admittedly, the doors and damper are probably not as tight as they might be. We also have a chimney cap. I read online that a damper at the top of the chimney with a pull chain might be a good idea, to keep any rain from coming into the fireplace and causing the smell. Is that what you would advise?

— ABBY SHAPIRO, NEEDHAM ABBY SHAPIRO, Needham

A. One answer to two questions, this time. The odor goes right down the chimney and into the house because high air pressure outside forces air down the chimney, bringing soot, creosote, and other noxious fumes into the house. It is called a downdraft, occurring when the stove or fireplace is not burning. Extra tight dampers, even on top of the chimney, do not work well. But adding a little heat will reverse that draft, forcing air and those odors up the chimney and out.

For the stove, light an old-fashioned railroad kerosene lantern and place it in the stove, with damper open. For the fireplace, buy a rack to hold votive candles and put it in the firebox, with damper open.

Q. I installed a wood stove this winter and it has really made a difference in cutting my oil bill. The problem is that the room where the wood stove is installed gets too hot and I would like to get that heat into our great room directly above. I understand that there are fire code laws prohibiting cutting a hole in the ceiling to circulate that warm air upward. Someone suggested installing a fusible link damper would satisfy those fire codes, but I can’t find much information about them. Would you please educate me on this subject?

— MARK TAGLIAFERRO MARK TAGLIAFERRO

A. I too struck out looking for information. So, I suggest you call your local building department or fire department for more information.

A back draft stopper

A caller asked if there is anything on the market to stop cold air from entering his house when his bathroom or kitchen exhaust fan is turned off. The Handyman did not know for sure, but he received this e-mail from David Lapollo, vice president of Tamarack Technologies, www.tamtech.com . Lapollo said, tell your reader to look at the Cape Back Drafter Damper. It slips inside the duct and has a fabric which closes on itself when a backdraft is trying to enter the exhaust of the bath fan. Placed inside the duct, just before it leaves the home, it will provide a solution to his problem. The Cape Back Draft Damper does not restrict exhaust air flow or (rob) the fan of any cfm. It simply closes when a slight bit of pressure tries to enter the home, through the exhaust port, into the duct.

The mold battle goes on

In response to Sally Rogers and her question on how to prevent future mold when there never was any, the Handyman OK’d her idea to treat the under part of the attic floor with a bleach/water solution. No, no, wrote Richard Fink, a certified biosafety professional.

“Spreading a bleach solution on the surfaces will do NO GOOD in preventing future growth of mold. Bleach does not leave a residue, you apply bleach and a short time later, all of the chlorine is gone and gone too is its ability to prevent growth of fungi. The only way to prevent recurrence is by having a water activity below what will support growth. There are some disinfectants that will leave a residue and thus give you a longer period of no growth while you dry the wetted surfaces. The most readily available to a homeowner is Lysol which contains a quaternary ammonium disinfectant, which kills and then leaves a residue that is highly fungistatic (prevents growth, doesn’t kill).”

And again, thanks, Richard. Extra, good information is always appreciated, and so noted.