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Lovern's Blog - Attic Mold

Whether it was discovered by an inspector while trying to sell your home or in the middle of some spring cleaning, here in Colorado, attic mold is a common issue. Mold growth in an attic can easily go overlooked for long periods of time because it’s not an area that most homeowners check very often. If left to grow for too long, the damage can cost a lot to remediate and can lower the value of your property. In an effort to save homeowners costs in unnecessary repairs, we have compiled a short list detailing 3 common causes of mold in the attic. I highly recommend checking for these issues in your home regularly, especially if you use your attic to store anything of value.

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1. Lack of Ventilation

It may sound strange at first - but most attic mold growth occurs during the winter, not the summer. A majority of molds will only grow in temperatures between 40-90 degrees Fahrenheit. In the summer, our attics are simply too hot to support any significant mold growth. There are a few specific types of mold that can grow in extremely low temperatures (such as Cladosporium), which is typically the species of mold that we most often find in our client’s attics.
The main reason attics in Colorado suffer from this problem is lack of proper ventilation. In the winter when we are heating our homes, some of that warm air rises into the cold attic. When properly vented, this warm air is able to easily escape outside. If the attic lacks proper ventilation, the warm air will become trapped and begin to condense on the cold underside of the roof. When warm air meets a cold surface, dew-point is achieved and this creates condensation. The condensation usually builds up on the roofing nails and forms water droplets that can drip onto the insulation and attic floor, causing mold growth.
In the photograph to the left, you can see frost and condensation forming on the underside of the roof. On the right, we see the beginning of mold growth in the insulation. Insulation is like a sponge; it holds water and is an ideal food source for mold. If the insulation in your attic is affected by mold, the IICRC S520 (the industry standard guideline for mold removal) recommends that it is discarded and replaced.

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2. Improperly Installed Bathroom Fans and Dryer Vents

I could not tell you how many times we have been called out to inspect an attic for mold, only to find that the issue could have been easily prevented. A large portion of these situations are due to improperly installed bathroom fans and dryer vents. The whole purpose of a bathroom fan is to direct humid air away from the home, so it’s extremely important that the ducting for these fans is connected to a vent cap and terminates outside.
In my experience, it is not enough to simply place an exhaust line directed toward the nearest roof vent because the humid air can still mix with the attic air and condensation on the underside of the roof can still occur. I also do not recommend running multiple appliances into a common vent line because excessive condensation can occur in the plenums and can even back feed into one or both of the appliances. Below is a photo of an incorrectly installed bathroom fan exhaust line that I discovered during an attic mold inspection. Excessive condensation was collecting at the top of the line and dripping back into the bathroom fan, eventually causing the appliance to fail and allowing mold to grow on the drywall around the fan.

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3. Existing or Previous Roof Leaks

This is probably the most obvious to detect out of the 3 main causes for attic mold, but it is so common that I have to briefly touch on it. Whether caused by an ice dam, deteriorated vent sealing, or cracked flashing, any moisture that enters the attic space has the potential to create the ideal environment for mold growth. Below is a photo of an attic that suffered from multiple leaks so the roof was repaired over the summer. Unfortunately, nothing was done about the moisture and mold left behind in the attic, and by the time I was asked to come out and inspect the property the growth was widespread throughout the entire attic. Laboratory testing of a surface sampled taken inside of the attic confirmed that this black substance was Cladosporium.

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I found black mold in my attic, what do I do now?

Because the EPA recommends that you hire a professional in cases where visible mold exceeds 10 square feet, the first thing you should do is contact a mold removal specialist, like the ones here at Lovern’s Inc. One of our certified mold inspection experts can inspect your attic any day of the year. The initial inspection and estimate are always free of charge. During this inspection we aim to determine the exact source of moisture, the extent of the damage, and how to correct any ventilation failures if any are occurring.
In most cases, the underside of the roof can undergo a surface cleaning. During this process, we isolate the attic from the other areas of the house, remove the insulation, HEPA vacuum the area, treat all attic surfaces with anti-microbial and finally seal the surfaces with your choice of a clear or white mold resistant sealant. After all the mold is removed and sealed, we are able to replace the insulation. The whole process usually takes about 2-3 days depending on the size of the attic.
I hope that by reading this blog you can potentially avoid a mold issue in your attic altogether, or at very least you can now feel a little more prepared to address a mold removal project in your attic. If you have any questions or would like to schedule a free attic mold inspection, please call us on our 24/7 emergency hotline (719) 573-8446.


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