An Ounce of Prevention . . .

Today’s post is going to be all about how to prevent HVAC system mold issues. I wanted to write this post, because some of the most prevalent and costly to remediate indoor mold problems (including the one my family and I suffered from) are caused from mold growth inside HVAC systems. Thus, it should also come as no surprise that, second to reader questions about cleaning their belongings that were exposed to mold, questions about HVAC mold problems are the ones I get most frequently. Often, readers write to me about frustrations with trying to effectively remediate their entire mechanical system and/or ducts (you should ALWAYS do both if this mold issue affects your home) or, because they want to know how to figure out if the musty smells in their homes are related to when their HVAC system cycles on and off—aka if the musty smells are coming out of their vents.

Factors That Can Contribute to HVAC Mold Growth:

To begin, I think it is important to discuss the many factors that can contribute to this major indoor air quality issue in the first place. I am no HVAC professional, building scientist, or microbiologist, but many elements of how we configure, use, and maintain our mechanical ventilation systems seem to me to be the root causes of mold HVAC problems. The reasons for this are many, but if I had to choose my Top 5, they would include the following basic principles:

1.)   HVAC systems combine all of the ingredients needed for mold growth (dust, aka organic material, high humidity, and water) perfectly inside one mechanical system;

2.)   Most HVAC mechanical systems are set up essentially out-of-sight in our homes and are housed in unconditioned areas, like our attics, basements, or crawlspaces. This makes regular maintenance, leaks, and/or visible microbial growth not something that is glaringly obvious or at the forefront of our minds on a daily basis; (This is in strong contrast to when flooding, or a major leak or water incident occurs in a highly visible or trafficked part of our homes.)

3.)   Almost all homes have central HVAC systems these days, so all indoor air is, at some point, channeled through the mechanical HVAC system. Thus, if you have mold growth inside of it, it is going to be blown throughout your home and is going to directly affect almost every, if not all rooms in your home and all of the air that you breathe when indoors;

4.)   Most people rely on HVAC professionals to maintain their systems (if they maintain them at all) and do not take the time to regularly inspect, clean, or check on their HVAC system to make sure that is functioning properly—this includes checking for leaks, having the coil and condensate pan cleaned, and changing and properly installing filters;

5.)   Visual inspections of an HVAC system aren’t always enough to find the culprit, because most mold problems occur inside the plenum or on the coil and cannot be found without some digging and mechanical knowledge, so that you know where to look.