To alert you to the possibility that backdrafting or another problem is occurring, every house should have carbon-monoxide (CO) detectors installed. Smoke detectors are required in all homes, but in many parts of the country CO detectors are not. Costing as little as $40 or so, CO detectors can alert you to a potentially dangerous buildup of the colorless, odorless, and tasteless gas.
As described earlier, carbon monoxide found in the house environment can result from improperly burning and venting fuel-burning heating equipment like furnaces, boilers, space heaters, and fireplaces. It can also come from gas or oil water heaters, gas ranges, clothes dryers, and even from automobile exhaust that leaks or is drawn into the house from an attached garage.
The usual recommendation is that a CO detector be placed in or near the sleeping quarters in a house. That way even if you're asleep, the alarm will alert you when the detector picks up the presence of the gas in the house. It is a good idea to place a second detector in or near the mechanical room. Venting malfunction is most likely to occur in this area. Municipal fire departments often have programs that give smoke detectors away for free. Some are starting to do the same with CO detectors.
Other Airtightness Issues
Many people observe that after they have some types of energy upgrading done in their homes, conditions inside change markedly, especially during the winter. One common scenario is that after a homeowner has her or his old windows replaced with new ones, she or he will start noticing excess moisture inside the house -- notably condensation on cold mornings on the inside panes of the new window glass. What happened?
Old windows are usually not very airtight. They allow air to infiltrate the house and also to leave the house. This sets up an uncontrolled ventilation pattern that removes moisture from inside the house (in the form of water vapor) and imports dry air from outside. The result is dry air inside during most of the winter -- a common complaint from those who live in leaky older homes.
Once the old, leaky windows are replaced with airtight new ones, that indoor moisture no longer has a means of escape. It builds up to levels that can create condensation on cold surfaces. Since window glazing is usually the coldest surface in most houses, that's where the condensation shows up first. This is one of the most common complaints to window companies. Customers who thought having new windows installed would rid them of condensation on their windows sometimes find just the opposite to be the case: They're getting more condensation than ever.
The new windows are not at fault. There is simply too much humidity in the house. The solution is to reduce the humidity level inside. After that the condensation is reduced or disappears.
Homeowners who undertake comprehensive air sealing in their homes often find similar problems with moisture buildup. They've cut off the ventilation that diluted the humidity and brought in drier air from outside.
Similarly, an upgrade to sealed combustion furnaces and boilers can lead to issues with excess humidity. The problem lies in the fact that drier outdoor air that used to be drawn into the house by the combustion process in the old furnace is no longer streaming inside. That means the air inside the house is not being replaced with outdoor air. Humid air that was formerly diluted with the incoming drier air is now predominant and condensation difficulties can crop up.
In the next section, we'll review how to protect the air quality in your home.