Step one of solving a problem is figuring out if there’s a problem in the first place! One of the top ways to promote healthy air quality in your home is to find whether or not there’s a source of contamination that’s causing issues. But where do you look for problems? Knowing the top places where mold is found in a home will help you quickly find any issues that need to be resolved.
The faster a source of contamination is eliminated, the less it will impact your indoor environment and air quality. This, in turn, will ensure you’re not suffering from unwanted exposures that can trigger a laundry list of chronic symptoms.
With that in mind, here are the top places where mold is found in homes.
What Causes Mold Growth?
Before grabbing a flashlight and starting the hunt, it’s important to know what mold needs to begin growing.
Mold thrives where there’s moisture. In fact, some species can begin growing within 24-48 hours, provided with a source of wetness and organic matter. So basically, where there's moisture, there’s an opportunity for mold. This means that rooms with high levels of water use, like kitchens and bathrooms, are at the top of the list for areas that develop microbial growth. Other situations like high humidity, leaks, and moisture intrusion from structural damage can also allow for microbial growth in a home. These issues should be addressed quickly and correctly to avoid any issues and minimize contamination levels.
Another factor to consider is areas of the home that we don’t frequently spend time in. Minor issues like a leak or improper ventilation that creates high humidity can continue until they’re discovered, allowing microbial growth to develop and flourish. On the same note, surfaces like behind the fridge or the HVAC often develop problems because they aren’t always adequately cleaned and maintained.
Items that use water are also at the top of the list for places for mold growth. The constant source of moisture creates perfect conditions for contaminants to move in. That’s why laundry machines, showerheads, and coffee makers should be kept as clean and dry as possible.
When mapping out a list of places where mold is found in homes, prioritize these areas since they often have the elements needed for growth.
Top Places Where Mold is Found in Homes
Without further ado, here are the top places where mold is found in homes.
- The attic: Attics are one of the top places in homes for contamination situations. Leaks, exhaust vents ending up there, and lack of ventilation can allow for moisture issues and create perfect opportunities for mold to grow. And, oftentimes, it occurs without you knowing and continues for quite a while because we only pop into these spaces to grab those holiday decorations.
- The basement: Basements are often damp, dark, and poorly ventilated, providing the ideal breeding ground for microbial growth. When mold grows in a basement, it can easily spread throughout the rest of your home, contaminating the air and surfaces inside.
- Crawlspaces: Faulty gutters, structural issues, plumbing leaks, poor drainage, and inadequate ventilation are some of the reasons these areas are prone to mold. And chances are that you rarely pop into the crawlspace, so these issues can go on for some time before they’re discovered.
- Underneath sinks: Chances are that these spaces don’t get much traffic unless you’re blindly tossing something down there for storage. With a water source right above them, though, issues such as leaks can quietly pop up and create ideal conditions for microbial growth.
- Grout and caulk: Over time, these materials can become increasingly porous, trapping water and creating a great environment for that fungus among us. Tack on cracks, misaligned tiles, and lack of cleaning, and they can quickly become sources of contamination in your home.
- Windowsills and doorframes: These are some of the top places where mold is found in homes for various reasons. When warm outdoor air meets the chilly indoor air, condensation can form along windowsills and door frames. Improperly installed windows and doors or degrading sealants allow moisture and humidity inside the home. Also, accidentally leaving windows and doors open during bad weather allows precipitation indoors. More moisture means more opportunities for microbial growth.
- Appliances (coffee maker, dishwasher, refrigerator water spout, blender, laundry machine, etc.): Gadgets like dishwashers, washing machines, and refrigerators all use water. If there's any moisture left behind after using them, that moisture can linger and provide the perfect breeding ground for mold to grow. Throw in organic matter like skin cells, soap scum, and mineral buildup, and you’ve got a perfect breeding ground for mold and bacteria. If these contaminants manage to settle in, every time you turn the machine on, you’re blasting all sorts of microscopic particles onto clothes, food, and beverage items, as well as throughout your home.
- HVAC coil: This is a component of many HVAC units, and it tends to condensate as the unit runs. It’s also not typically on the list of frequently cleaned areas in the home. This creates a perfect environment for microorganisms like mold or bacteria to grow and thrive.
- Exhaust vents: Without proper cleaning, these vents can develop a layer of dust and other organic particles. They can also begin to harbor moisture in this layer of grime, creating the perfect situation for microbial growth.
- Showerheads: When it comes to these fixtures, moisture is in abundance. Then, add in the mineral buildup, particles in the water, and all the organic specks floating around, and you have the ultimate spot for contamination to pop up. Which then means you’re showering in mold…
- Sink faucets: As these fixtures provide running water, it’s easy to see how they made it to the list of top places where mold is found in homes. Without proper cleaning, organic material like mineral buildup creates a perfect, hidden spot for microbial growth.
- Houseplants: Houseplants can be a great addition to a home. Some studies have even linked them to improving our wellness by reducing stress, boosting productivity, and increasing our sense of well-being. However, mold can develop in the plant or the soil, turning these indoor plants into a health hazard. Then you’re not only feeding and watering your plant but also that fungus among us as well.
- Fireplace: Leaks, broken chimney crowns, and damaged mortar can all lead to one thing: moisture intrusion. And where there’s moisture, there’s an opportunity for that fungus among us to move in.
Pro Tip for Where Mold is Found in Homes
My favorite trick to help determine if there’s an indoor contamination problem is to check the toilet tank for mold. While the lid isn’t hermetically sealed, there’s very little air transfer between the inside and outside of the tank. A lucky spore could have found its way inside, but it’s far more likely that there were enough spores in the air from another mold colony in the home, leading to it opportunistically beginning to grow in this location. You're much less likely to find mold in the toilet tank than in other damp areas like the bathtub caulking, so if there’s microbial growth inside this area, there’s probably a larger problem elsewhere in the home.
Why Knowing Places Where Mold is Found in Homes Matters
As mold grows, it reproduces by creating microscopic spores and sending them into the surrounding space.¹’² Some species of mold can also create microscopic toxins called mycotoxins when threatened, further adding to the level of contamination.³
The longer a colony thrives and survives, the more particles will be blown all around. This isn’t a problem in nature because there’s a wide world to disperse. Mold in a home is not the same scenario. Thanks to modern building techniques pushing for net-zero energy efficiency, there’s very little airflow between indoor and outdoor environments. That means that most of the microscopic particles produced by the mold, not to mention fragments from the colony itself, are trapped within the home's walls.
This leads to:
- Poor indoor air quality
- Contaminated surfaces throughout the home (these particles can ride the indoor air current anywhere)
- Increased likelihood of a colony opportunistically developing elsewhere in the home
To add another layer of contamination problems, bacteria thrive in environments similar to mold.⁴ That means that where there’s mold growth, there are often bacteria as well.
This situation can create a toxic indoor environment. As the average individual breathes 20,000 breaths per day and spends 90% of the time indoors, the state of our indoor spaces matters. Let’s say your home has a current mold problem. Every time you sleep, sit down for dinner, turn on your favorite TV show, or host game night with friends, you’re breathing in all sorts of microscopic particles.
Just because you can’t see them doesn’t mean they’re not there. That’s one of the main dangers of indoor mold growth. It can be present and cause the air quality to plummet without anyone knowing. Over time, these particles will continue to build up in the home and the body and can cause all sorts of adverse health reactions. ⁵’⁶’⁷’⁸’⁹
Knowing where mold is found in homes can help avoid this toxic situation and ensure your environment remains the haven you want.
How to Look at Places Where Mold is Found in Homes
Knowing where to look is the first step toward success. But what exactly are you looking for? It’s a great question!
While combing through your home, pay close attention to these five indicators of microbial growth.
1. Visible Signs
Visible growth is one of the most straightforward indicators of a problem. There are over 100,000 species of mold identified around the world so far. With so many in existence, mold and mildew can come in a variety of colors, shapes, and textures. Some of the most common colors include green, pink, white, grey, blue, red, black, brown, or a combination of hues. As for textures, they could be fuzzy, powdery, velvety, or slimy.
A noticeable odor can indicate a contamination situation indoors as well. Microbial growth isn’t always visible. The colony could be behind a wall, underneath the flooring, or in another hidden location. Using our sense of smell can alert an individual to a hidden problem.
Colonies can create an earthy, musty, damp, cigar-like smell due to the release of gases called microbial volatile organic compounds (MVOC). If this odor is present in a home, it points to a problem.
3. Chronic Symptoms
Chronic health issues with seemingly no underlying cause can also indicate microbial growth indoors. Spores, fragments, and potentially mycotoxins circulate throughout the environment as the fungal growth continues indoors. These particles are small enough to be inhaled, ingested, and absorbed into the body, potentially leading to adverse health reactions in those exposed. That’s essentially the alarm bell sounding that something isn’t right. It’s up to us to listen to these signals and figure out the root cause to eliminate it. If these pop up and worsen inside the home, it can indicate an issue within.
Pay attention to your body while looking at the top places where mold is found in homes. If those systems start lighting up like a Christmas tree in certain areas, it indicates a problem.
4. Water Damage
Water damage in a home can indicate microbial presence inside, creating the perfect opportunity for growth.
Signs to look out for include:
- Coffee-like stains on ceilings or walls
- Discolored carpeting
- Peeling, cracked, or bubbling wallpaper
- Peeling or bubbling paint
Structural issues such as cracks in the foundation can also indicate possible water intrusion and an opportunity for microbial growth.
Taste can be another indicator, depending on the location of the contamination. Appliances are at the top of the list for microbial growth thanks to the abundance of water and organic matter they use. Contamination could be present if a funky taste pops up in items such as the coffee maker or blender.
Check out this blog for more information on these signs and what to do if you discover mold.
Not Sure if There is a Problem?
If you’re unsure if there’s a current contamination situation, use a tool like The Dust Test.
Gravity brings particles like mold spores, mycotoxins, and endotoxins down to horizontal surfaces like floors, doorframes, and furniture. Where dust collects, so do these indoor contaminants.
Testing this dust will help to determine exactly what’s hanging out in your home and potentially causing problems. Highly contaminated dust is a health hazard as all those particles can enter the body when they’re kicked up into the air when the dust is disturbed. It also indicates an underlying contamination problem somewhere in the home.
The Dust Test will help you know if there’s a problem before spending thousands of dollars trying to find one (both medically and in your home). And, if there is a problem, The Dust Test will indicate what you’re being exposed to before your inspector comes so that you can ensure they will find where it’s coming from.
A good idea is to test your dust annually to ensure no hidden problems.
Promoting Your Healthy Space
Prolonged exposure to poor indoor air quality and contaminants like mold and bacteria can seriously impact our wellness. Reducing exposure by eliminating microbial growth in your home will ensure you’re breathing easier. Keeping an eye on the top places where mold is found in homes will help ensure you catch any problems early so they can quickly be addressed.
It’s a win-win all around!
When in doubt, contact an expert to get their advice on creating your healthy indoor space.
- Environmental Protection Agency. (n.d.). Mold. EPA. Retrieved from https://www.epa.gov/mold.
- Centers for Disease Control and Prevention. Basic facts about mold and dampness. Centers for Disease Control and Prevention. Retrieved from https://www.cdc.gov/mold/faqs.htm.
- World Health Organization. (n.d.). Mycotoxins. World Health Organization. Retrieved from https://www.who.int/news-room/fact-sheets/detail/mycotoxins.
- Taylor, S. (2019, March 2). What three conditions are ideal for bacteria to grow? Sciencing. Retrieved from https://sciencing.com/three-conditions-ideal-bacteria-grow-9122.html
- Nchh. (n.d.). Mold. NCHH. Retrieved from https://nchh.org/information-and-evidence/learn-about-healthy-housing/health-hazards-prevention-and-solutions/mold/
- Environmental and Occupational Health Assessment Program, & Environmental and Occupational Health Assessment Program, & Health Science Section, Mold Basics for Primary Care Clinicians (2009). Hartford, CT; Connecticut Department of Public Health. , H. S. S., Mold Basics for Primary Care Clinicians 1–10 (2009). Hartford, CT; Connecticut Department of Public Health.
- Curtis, L., Lieberman, A., Stark, M., Rea, W., & Vetter, M. (2004). Adverse health effects of indoor molds. Journal of Nutritional & Environmental Medicine, 14(3), 261-274.
- Bush, R. K., Portnoy, J. M., Saxon, A., Terr, A. I., & Wood, R. A. (2006). The medical effects of mold exposure. Journal of Allergy and Clinical Immunology, 117(2), 326-333
- Fisk, W. J., Lei-Gomez, Q., & Mendell, M. J. (2007). Meta-analyses of the associations of respiratory health effects with dampness and mold in homes. Indoor air, 17(4), 284-296.
- Wild, C. P., & Gong, Y. Y. (2010). Mycotoxins and human disease: a largely ignored global health issue. Carcinogenesis, 31(1), 71-82.
- Bennett JW, Klich M. Mycotoxins. Clin Microbiol Rev. 2003 Jul;16(3):497-516. doi: 10.1128/CMR.16.3.497-516.2003. PMID: 12857779; PMCID: PMC164220.