What causes attic mold?

Posted by Matt Buchanan

If you’re like most of us, you rarely if ever venture into your home’s attic. Why would you? It’s not usually a place you care to venture and for the most part if you do it’s because something isn’t going well. With warmer temps here for the summer, we start to see an increase in jobs where homeowners have discovered black mold damage in their attic. In this blog post, we’ll talk through what we typically see when homes have considerable amounts of attic black mold and help you understand ways you can make sure it doesn’t happen to you.

 

Why black mold grows in attics

 

Black mold damage in your attic space occurs for the same reasons it occurs anywhere else in a dwelling. It’s a combination of a few things:

() the right temperature – mold spores like warmer, ambient temps. In fact, it likes about the same temp range as we do, between 60-80 degrees Fahrenheit.

() food – no, not crumbs from discarded food a home service technicians might have left while doing some work up in your attic long ago. Black mold eats anything that is high in cellulose. Unfortunately for homeowners, that’s pretty much anything in your attic, like plywood, wood joists, roof decking, etc.

() elevated moisture – many homeowners don’t realize that moisture is found in every surface of their home, as it should be. If those surfaces were completely devoid of moisture they wouldn’t perform their duties properly. But if a surface gets too much moisture in it, that’s the trigger black mold needs to start growing. Another thing most homeowners don’t realize is that black mold spores are present in most environments, and certainly in every home or other type of dwelling. It exists naturally and in low levels and is completely harmless to humans and pets. But with the right conditions, it can grow quickly and spread, causing wide spread damage to your home and have potentially serious health consequences for the home’s inhabitants.

As you can see from the list above, 2 of those things are normal. It’s the 3rd thing, elevated moisture, that is not normal and creates the right environment for a serious mold problem. So now let’s talk through how moisture gets into attics and what you can do to make sure it doesn’t get into yours.

 

Causes of attic black mold growth

 

When we are called to a home and discover toxic black mold in the attic, the culprits are usually pretty easy to spot. There are only so many ways moisture finds its way into an attic. Here’s what we usually see:

 

Venting directly into the attic

Many bathrooms are equipped with vents that take the warm, wet air released when a shower is running and remove it from the bathroom. Unfortunately, sometimes a misguided homeowner or shoddy handyman will simply install the vent fan such that the air is pushed into the attic where it has nowhere to escape. Here is a quick article (with video) that explains the proper technique for installing a vented fan into an attic space. If you have an older home that is equipped with one or multiple of these types of exhaust fans, it’s probably worth you taking a look in the attic space to make sure it’s vented properly.

 

Condensation from an AC unit in an attic

In some areas of the country, HVAC companies will install AC units in attics. These units produce condensation that must be vented and drained properly or else it can allow moisture to find its way into your attic. Manufacturers recommend you inspect your AC unit before you turn it on for the summer as well as at the end of the hot months to make sure it’s running properly and so that you discover any potential moisture problems before the get too bad.

 

A leaky roof

By far the biggest culprit we find when inspecting an attic with black mold is a leaky roof. Just one damaged or misplaced tile can allow rain water to slowly seep into your attic. While most people picture a deluge of water coming through their ceiling, more often than not a rook leak will just allow a slow amount of rain water to enter the attic, usually soaking the roof deck and eventually dripping down onto the attic floor and/or your exterior walls. We always recommend that you (safely) inspect your roof’s exterior each spring and it’s also a good idea to just crawl up into your attic and peer at the interior decking of the roof. If you start to see staining, it’s a sign you have some moisture intrusion that needs to be addressed!

 

About Matt Buchanan

I grew up in Irving, TX and left for Nashville, TN for college. After college I lived in Washington, DC and then in Cairo, Egypt. After coming back to the states, I spent a couple of years back in Dallas before moving with my wife to Denver!
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