Feb 1, 2014 8 min read

Q. My father lives in a small cape built in the ’50s. It has forced hot water heat. The upstairs is generally at least 10 degrees warmer than the downstairs where he spends all of his time, therefore wasting a lot of heat. We’ve tried bleeding the radiators and turning off the radiators. The thermostat is downstairs. The burner is fairly new (replaced five years ago).

The burner guy doesn’t know what to do about this other than what we’ve done. Should we have a thermostat put in the upstairs? Perhaps we are not bleeding the radiators correctly – could you explain this? Or should we contact our service and have them try again?

Martha Monohan

A. Bleeding the radiators might make them more efficient, but what confuses me is that turning off the radiators upstairs makes no difference. Call your burner man to see if the upstairs heat can be stopped. Adding a zone or an upstairs thermostat should work, too, and that should be done by the burner man.

Q. I live in a 13-year-old well-constructed home, but this winter I have begun to notice a problem with window moisture and its effects on the window frames. During the cold of winter, we run a humidifier. However, whenever the temperature has dropped much below zero, we have developed a slight rim of condensation along the bottom of some windows. This has led to the deposit of a black substance along the woodwork. We do not have an air exchange system, though I do not understand how that would prevent any problem other than to reduce internal moisture that we are trying to replace with the humidifier.

My questions:

• What is this black substance?

• Will this cause any long-term damage to the woodwork?

• Is there a way of avoiding it other than turning off the humidifier or replacing with windows of higher insulation value?

• Is there any treatment for woodwork that already has a black deposit?

• What is a full house air exchange system other than a system that removes internal air and replaces it with a dryer colder external air that needs to be heated?

John Virant, St. Paul

A. Turn off the humidifier, which is causing condensation and the black stuff, which is mold. Remove the mold with a solution of 1 part bleach and 3 parts water. I think people in very cold climes may not know what mold is or looks like, because the colder the area, the less likely mold will grow. Mold can be other colors as well. Use the humidifier sparingly, and shut it off if you see mold anywhere.

As for the rest of the questions: Mold can ruin a painted surface over time. Keep the house dry(er) to prevent mold. Treat it with the bleach/water solution.

Finally a full-house air exchange is not what you think it is, because it exhausts humid air and brings in fresh outdoor air, and transfers the heat of the outgoing air to the incoming air, at little loss of heat. I suggest you invest in an air-to-air exchanger, which should have been installed anyway because your house is extremely tight and has a low exchange rate.

Q. My garage roof has half-dollar and quarter-size greenish yellow blobs on parts of the roof. What can I do to eliminate this problem?

Martin Finn

A.Those are lichen, a combo of algae and mold, and sometimes they are difficult to remove. Try soaking them with water and scraping with a wood spatula, being careful not to gouge the shingles. If that doesn’t work, soaking them with vinegar will kill it and make it easier to remove. If none of the above works, let it be. The lichen is harmless, only a bit unsightly. Sometimes you may see it on trees. It doesn’t hurt the trees.

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

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

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

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

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.

In response to a question on how to prevent future mold when there never was any, the Handyman OK’d an 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 that 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.