Attic Mold – What It Is And How To Deal With It

There are few places in the home that attract mold easier than the attic. They often have the perfect conditions for mold growth – hot or humid air, and an abundance of wood sheathing just waiting to grow mold. Furthermore, homeowners rarely check the attic and find themselves with a mold problem that they don’t even know they have.

In this article, we discuss how to identify attic mold issues, their typical causes, and how to act on them before it’s too late.

How to know if you have mold in your attic

You can avoid an attic mold problem by either routinely checking the area for mold, or by taking necessary precautions to make sure it never happens. But you don’t know if you have an attic mold if you don’t know what you’re looking for, so here are the telltale signs of an attic mold problem.

Getting into an attic and completing a detailed inspection is tough work! Don’t want to deal with the hassle? Schedule a free attic inspection today and learn how to save energy and improve comfort in your home.

Hot and stuffy attic

Ideally, you attic should be breezy and have good air circulation. If you have proper ventilation this shouldn’t be a problem, but when you have a stuffy attic you’re increasing the chances of accruing mold.

Frost buildup on the underside of roof sheathing

During colder months, poor ventilation can cause the water vapor in the attic to freeze on the underside of the roof. This frost buildup is easy to spot and a clear indication of future mold.

Wet attic insulation

This is not only a surefire way to get yourself a mold problem, but wet or damp insulation hinders its abilities. This is going to cost you extra money to heat or cool your home.

Water dripping from smoke detectors, fans, and light fixtures

If water is coming out from these ceiling fixtures, that means the floor above you – in this case the attic – has moisture that needs to be addressed.

Mildew smell in the attic

A musty or moldy smell in the attic generally means that there’s mold already developing. Trust your nose! Read our detailed post more information on what mold smells like.

Dark staining on wood surfaces

If the wood in your attic has any black discoloration, that means the problem has moved beyond moisture, and that there is mold that needs to be removed.

What causes attic mold?

Mold is a type of fungus that thrives on moisture and reproduces through lightweight spores that travel through the air. Therefore in most homes, a mold problem is likely a moisture problem. You can’t have a mold issue without first having some sort of moisture issue.

In most cases, attic moisture problems are due to three different elements: blocked or insufficient ventilation, improper exhaustion of fans or dryer events, and roof issues or leaks. Let’s discuss each of these three issues so you can have a better understanding of how to fix a mold issue before it occurs.

Blocked/Insufficient Ventilation

You may have figured out by now that the most common cause of attic mold is blocked or insufficient ventilation. Attics generally have a passive ventilation system in which outside air comes in through eave vents, warms up the attic, then escapes through a can or ridge vent at the top since warm air rises. This creates a nice, breezy airflow for your attic – until your eave vents become blocked.

This disrupts the entire ventilation system, and your attic becomes hot and stuffy. The warm and humid air in the attic will stagnate and condense along the cold wood sheathing in the winter. This then causes wet wood and mold growth throughout the attic.

Mold growth can also occur if there aren’t enough vents, as 1 square foot of venting is needed for every 100 square feet of attic space. Most home inspectors or contractors will check your house’s ventilation system whenever there’s a mold problem, so be ahead of the curve by checking if your house has a proper system unblocked by insulation.

Improper bathroom fans or dryer vents

Dryer exhaust vents, bathroom exhaust fans, and kitchen exhaust fans are designed to pump moisture out of your home. Always make sure that they’re terminating outside of your house, and not into your attic. Plumbing stacks can be a source of condensation in the attic, which often lead to mold growth. Since plumbing stacks can release hazardous substances, make sure they’re not terminating inside your attic either.

Roof issues and leaks

Roof leaks often lead to smaller, more centralized areas of attic mold near where the leaks are occurring. Here are a few ways to check for roof leaks:

• Check for dark discoloration or staining of wood like rafters, joists, sheathing, etc.
• Check roof valleys (aka where two roofs join at an angle), as they are susceptible to roof leaks
• Observe vents, plumbing stacks, chimneys, and anywhere else where dissimilar materials join each other, as they are hotbeds for moisture intrusion.

Does attic mold affect indoor air quality?

Given all these precautions for attic mold, you might be wondering why it can be so hard to notice until it’s too late. Part of that is because attic mold doesn’t necessarily affect the quality of air inside your home.

This is due to the simple fact that warm air rises, a phenomenon known as the “stack effect,” in which air rises from the lower levels of your home to the attic. Since mold spores don’t have wings – as in they can’t fly against the upward flow of the stack effect within a house – it’s extremely rare for attic mold to affect the indoor air quality.

However, attic mold is a common issue that homeowners don’t know they have until other issues arise. Although there are plenty of professionals that can remove attic mold, it’s also better to prevent it from happening in the first place, even if it doesn’t directly affect the air in your house.

How to prevent mold in your attic

Air Sealing

We’ve already identified how bathroom or kitchen fans can end up dumping moist air into the attic instead of outside the home. In the wintertime, the cold wooden sheathing in the attic combined with the moist air can cause wet wood which results in an ideal environment for mold to form.

To prevent moist bathroom or kitchen air from exiting into your attic, technicians can seal the attic and make sure that vent fans and dryer vents are ducted to the outside. This way none of the harmful moist air enters the attic, and instead is redirected outside the house.

Proper Ventilation

Similarly, make sure that all of your appliance, plumbing, and house vents are all directed to vent outside, not the attic. Your vents might also be venting to vent ports installed in the soffit, and warm air might not be traveling in the downward motion that they’re designed for. Check for stains and discoloration above where the vent enters the soffit areas to diagnose potential issues.

Air constantly moving through the attic will ultimately prevent mold from developing, so it’s hard to overdo the ventilation up there.

Proper Insulation

Another key component to keeping mold out of your attic is proper insulation. Insulation prevents warmer air from entering a cold attic, as that causes condensation and moisture buildup. Check that there is insulation on and surrounding your access panel and your attic floors. Heating ducts and any empty space between the attic and other parts of the house (such as crawl spaces).

Don’t over-insulate your attic, as warm air is ultimately needed to dry out some of the moisture in the attic’s air. No heat to dry out moisture means mold growth in your attic.

Benefits of preventing mold in your attic

When unattended, attic mold can lead to structural deterioration of attic sheathing and the roof. Repairing these components can get expensive depending how widespread the damage is. Preventing mold through proper ventilation and insulation can save homeowners a fortune.

Furthermore, properly ventilating your home and preventing mold from forming around ventilation in your attic will allow better overall air circulation. This will make your attic less stuffy in the summer, which contributes to a cooler house overall. As such, preventing mold through proper ventilation can help save you money on electric bills.

It’s always best to check your home for any warning signs and deal with them accordingly so that your house is free of mold and you are free of worry.