Controversial? Yep. True? Yes, with caveats.
Let’s begin with a basic review of the relevant factors that allow mold growth to occur. In nearly all circumstances, this comes down to available moisture and food source. Yes, we can talk about temperature requirements, but we’ve all observed mold happily growing in our 35 degree refrigerators. In all but the most unusual circumstances, the temperatures we humans prefer to live in correlate well with the temperatures mold prefers.
First up, moisture.
Mold requires a minimum amount of available moisture to grow. Thankfully, in all but the most humid environments, mold requires more moisture than is commonly found in our building environments. Exceptions to this include cellars or other areas that require high humidity conditions. One could also make the case for exterior siding in cool damp climates such as the Pacific NW, where normal buildings can suffer from mold growth. However, in most situations, mold growth requires an unusual amount of moisture, an amount of moisture caused by a building defect. This may be a structural defect, such as a leaky roof, or a design defect, such as poor ventilation.
Why is this relevant in our discussion of mold preventative coatings? In short, if we properly address the elevated moisture conditions, we’ll prevent mold growth more effectively than the most advanced preventative coatings available. Viewed this way, mold prevention coatings are a cover up solution that fails to address the underlying cause. Ok, but what if the coatings worked perfectly? Even if this were true (and it is not!), elevated moisture conditions cause many other problems besides mold growth.
Consider a home with elevated humidity suffering from mold growth. Imagine, for a moment, that we apply a perfectly effective mold inhibitor on every surface in the home. Yes, this would theoretically deal with the mold problem. But if we didn’t address the underlying humidity problem, we’d still leave the client with conditions highly conducive to dust mites and other allergens. Other IAQ issues, such as elevated contaminants are typically present with elevated humidity as well. The solution? Address the underlying humidity and ventilation issues and we not only address the mold problem, but also dust mites, odor buildup, VOC problems, etc.
What about future moisture issues? Good question! Mold preventative coatings are often marketed as the solution to unknown moisture issues that may strike in the years to come. A plumbing leak? No problem. The XYZ mold inhibitor will stop mold growth before it starts. This sounds great in theory, but quickly falls apart in actual building environments.
The problem is due to a settled dust. Any surface, whether vertical or even inverted, quickly accumulates a thin layer of settled dust. This settled dust is comprised of many types of particulates, but a significant amount comes from human skin, pet dander and other organic compounds. These unfortunately provide a perfect food sources for mold growth.
Now apply this to a mold prevention coating. A contractor applies the coating throughout the home. For a few weeks, no mold growth is possible, as the mold inhibitor does its job. However, within a short while, a thin layer of dust settles on the surface. As mentioned before, this deposit of dust is a perfect food source for mold, and thus quickly renders even the most powerful coating absolutely useless.
Herein lies the caveat. Mold prevention coatings can be useful if you only need to buy yourself a few week’s time. For example, if you’re framing a house in the winter and saturation is inevitable, a mold inhibitor coating can prevent mold growth while the building is dried out. In every other circumstance, a mold prevention coating is worth very little.
Need a bit more proof? Below is a photo of heavy mold growth on a nylon backpack. Nylon, of course, is not a food source for mold growth. Yet mold had no problem attacking the layer of dust and debris found on the surface.