Around the house: Older fireplace needs a little fresh air to keep you safe

May 26, 2013 Updated: May 26, 2013 at 9:00 am

Dear Ken: I live in a 40-year-old house, and I use the fireplace a lot. The gas company said I needed a fresh air pipe to the utility room because when the fireplace and furnace are operating, there wasn't enough air. Do you think I can use the fireplace now? - Roger H.

Answer: You're probably OK. About 30 years ago, when the first oil price shocks hit, we started sealing up houses to save energy. Before that, a typical home leaked enough air around the windows and doors and through the attic and basement to satisfy combustion air requirements. When appliances, such as the furnace and water heater, burn natural gas, they use oxygen. This also applies to your wood-burning fireplace. It drafts huge quantities of air out of the chimney, lowering indoor air pressure. Why is that a big deal? To replace that deficit, the furnace and water heater can "spill" fumes from their flues and contaminate the indoor air with deadly carbon monoxide.

For the past 25 years or so, a separate feed of outside air has been required to dump directly into the fireplace. I'll bet you don't have such a vent in your older home. So, it's a good idea to crack a window in the same room as the fireplace. Plan your evenings so the fire has died when you retire. In addition, you should have a set of glass doors to isolate the combustion process from the indoor air space.

Dear Ken: I have some water on the floor of my kitchen sink cabinet. I can't figure out where it's coming from. There are no obvious leaks in the plumbing. Can you help? - Sonya K.

Answer: I'll bet you have a spray hose. They almost always dribble a little from the nozzle when you put it back in the hole. The water travels down the hose and forms a drip at the bottom of the loop; and that liquid inevitably lands on the floor of the cabinet. If you've used the sink continuously, the puddle might amount to a teaspoon or more. That's why I recommend a layer of vinyl floor covering or plastic-coated shelf paper under the sink. Overnight, the drips will evaporate, having caused no appreciable harm to the cabinet floor.

Dear Ken: I have some mildew stains on my ceiling and walls. Is this a matter of insulation? Or vents? - Janet C.

Answer: These stains typically reflect excess moisture inside the concealed spaces. Moisture from cooking and bathing travel part way through the walls and ceiling and then condense. That moisture encourages the growth of mold.

You need to attack this in two ways. First, make sure the indoor air humidity is low. Have the furnace and water heater checked for blocked flue pipes, turn down the humidifier, cover the crawl space dirt with plastic and use vent fans in the kitchens and baths. The goal: keep the indoor air relative humidity to around 40 percent or lower.

Second, check the attic. It needs to be isolated from the living space. Vent fan ducts should dump directly to the outside - not into the attic. Also, add some venting. The most effective styles are gable vents in the end of the attic, or the spinning turbines. Also, check those little soffit vents behind the gutters to make sure they are wide open. Once you get the moisture under control, you can seal them with KILZ and re-paint. Finally, check the attic insulation to make sure it's not damp. If it is, replace those sections.


Ken Moon, a homebuilder-turned-home inspector in the Pikes Peak region, broadcasts "Around the House," on KRDO, AM 1240 and FM 105.5, at 9 a.m. Saturdays. Visit aroundthe to contact Ken.

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