Mold—especially black mold—is dangerous to your health. So the last thing you want is to spread it around your home or to create an environment where it can grow. Your heating and cooling system is largely responsible for keeping your house mold-free.
Mold Basics
Molds are fungi that are present in nature. They reproduce by releasing microscopic spores that are tiny enough to be carried through the air on currents, or on clothing or other items, according to the U.S. Environmental Protection Agency,. There are thousands of different kinds of mold, so mold varies in appearance and color. Most commonly it appears fuzzy and is green, but mold also can be slimy and appear brown, black, white, yellow, or even pink, depending on the type, according to the Rhode Island Department of Health.
Mold thrives in warm, dark, damp areas and grows on any organic matter. So, it can grow on things like wood or food remnants in the garbage, and is most common in areas of the home where moisture or high humidity is present, such as on a bathroom or basement wall or along piping. Lack of air circulation allows mold spores to grow undisturbed in the home.
Mold and Your HVAC
Ventilation
Your heating and cooling system (HVAC) is responsible for distributing both hot and cold air throughout the house, as well as keeping the house properly ventilated. A good HVAC thus has a design that allows for efficient air flow. When air does not circulate in your home, mold spores have a chance to settle and grow on organic surfaces. In turn, n HVAC that does not provide proper ventilation contributes to mold colonies, especially if the HVAC also is not cooling properly.
Temperature and Humidity
As outlined above, mold thrives in warm, humid environments, so making sure that your HVAC lets you control temperature and humidity in your home is crucial to mold prevention. When your HVAC is unable to keep your home cool, the air in your home becomes warmer and is able to hold higher levels of moisture. Mold spores that normally would not have grown as prolifically suddenly are in a better position to reproduce. As the mold grows, spores can be drawn into the HVAC and distributed to every corner of your home. Try not to set your HVAC to a temperature above 75 degrees. At 75 degrees and above, most types of mold thrive.
If possible, have a dehumidifier installed in your HVAC system. This will allow you to monitor the amount of relative humidity in the air and keep the moisture level of your home below the point at which mold can rapidly grow.
Design and Locality
You should inspect your HVAC design if you suspect that it is contributing to a mold problem in your home. The more turns, vents, and filters in the HVAC, the more places there are for mold to grow within the system. Additionally, boiler systems can be more problematic than gas furnace systems because they operate using hot steam, which of course creates a warm, moist environment for mold. If any of the pipes in a boiler system become compromised, mold can contaminate nearby surfaces, such as the wood of the nearby walls. Additionally, your HVAC may be the problem if you find mold on windowsills after seeing condensation. In a poorly designed HVAC, vents can be right underneath or near windowpanes. When the warm air from the vent hits the cooler surface of the window (especially in winter), the moisture condenses on the window. If left unchecked, moisture makes the windowsill damp and mold spores take over.
Can You Fix a Mold Problem in Your HVAC?
Although a lot of home maintenance issues are do-it-yourself, a mold problem in your HVAC is not. The U.S. Environmental Protection Agency does not recommend cleaning the ducts and filters to remedy mold issues because doing so rarely kills all the mold spores. Thus, if your HVAC is contaminated, you may need to call in a professional and have the system reworked.
