Skip to main content

Mold In Attic: Causes & How To Remove It

mold in attic: causes and how to get rid of it

Mold in your attic. Will it harm you or your home? How do you get rid of it? Let’s dive right in!

Causes of Mold in Your Attic

If you find black spots in your attic and you are thinking it could be harmful black mold, you do not necessarily need to panic.

Mold located on ductwork, on roof decking, trusses, or just about anywhere in the attic is simply a problem of excessive moisture.

Mold will survive in almost any environment that is the right temperature, has moisture (even in the air), and has something for food (e.g. dust, drywall, wood).

So, in order to stop the mold we need to stop one of those three things. Moisture is really the only one we can control in our attics.

How Does Moisture Get In Our Attics?

To further talk about how mold gets in our attic we need to find out how moisture gets in our attic.

To break it down, your house is heated in the winter. When you heat air, the heated air holds more moisture and rises to the ceiling.

The hot air then finds tiny cracks and holes in your drywall through air vents, light fixtures, and wall junctions to enter the attic space.

Once in the attic, the hot air mixes with the cold winter air and begins to dew on materials, with the most common material being the roof decking.

Once dewing, the water can drip onto your drywall which causes staining on your ceilings or can create mold.

TL; DR (Too Long; Didn’t Read): Hot, humid air rises into your attic, mixes with the cold winter air and condensates causing staining and mold.

There’s also this handy video that explains how mold gets in your attic in northern climates. However, you may or not need remediation suggested at the ending. Read on to find out.

mold on trusses

How Mold Gets In Your Attic In Southern Climates

In southern climates, especially near beaches where there is high humidity, we actually get mold in our attics quite frequently.

In Florida it is actually common to have mold on the outside on of your ductwork.

This is because the humidity is so high, it can reach cool points in the attic and condensate.

An Additional Way Moisture Can Get Into Our Attics

A common occurrence in Florida is having bathroom fans vent directly into the attic. In Florida, this is usually fine because the attics are well ventilated and the attics are already super humid throughout the year.

On the other hand, if you were to do that up north the humid air would instantly combine with cool air in the attic and begin to dew causing mold/staining.

So, check your bathroom fan vents to see where they are venting to. If you are up north, they should be venting to the exterior.

Is Mold On Your Ductwork a Problem?

Well, in many cases not really.

HVAC technicians may try to sell you on new ductwork, but in southern climates near the beach, mold being on the outside of the ductwork may not be a big deal.

As long as moisture is not sweating too much to cause puddles of water, staining, and damaged materials!

For more information on the science behind dew points and condensation read here.

black mold in attic

Is Mold In Your Attic a Problem?

Is mold in your attic a problem? Yes.

While you should address mold in your attic of a large extent, smaller areas of mold may not be an issue.

Why Mold In Your Attic Is A Problem

Mold is naturally occurring in your environment, but too much mold can be harmful on your body and on your home.

Explained above, mold is caused by moisture. Moisture in your attic can lead to ceiling stains, mold, and damaged home materials.

So basically, mold can become a problem when there is excessive moisture that eats away at building materials (decays wood), or begins to condensate so much that it is causing stains on your ceiling.

Of course, with everything wet, it will cause more mold and can be harmful to breathe in.

How To Get Rid of Mold in Your Attic

There is a straightforward fix to getting rid of mold in your attic. That is, seal your ceiling.

You can use spray foam to seal all the tiny cracks in your ceilings. Just be sure you are purchasing the right spray foam, it should be fire-rated and for insulating.

These cracks, as mentioned above, could be from light fixtures, drywall junctions, attic ventilation, plumbing stacks, anything that goes into your attic and penetrates your ceiling.

Pro Tip: An easy way to find the areas of concern is to go where the mold is. So, if the mold is on the roof decking, the air is probably leaking right below that area.

Another Pro Tip: If you have a thermal camera you can see where air is leaking by scanning the ceiling for “hot spots”. These are areas where there is poor insulation.

A word of caution: Only do this if you are handy and understand how to walk in an attic. You could fall through the ceiling!

Use This Video Below For Tips on Air Sealing Your Attic To Get Rid of Mold

What To Do About The Existing Mold?

This is kind of debated.

In my personal/professional opinion, once you stop the moisture you will stop the mold and it will go away naturally.

However, if you have a large issue that is getting into your home you might want to have remediation done.

Some companies will try to up-sell mold remediation in your attic, but in most cases I do not see a reason for it since you are not spending your time in the attic.

I would always recommend having an inspection done by a third-party licensed home inspector before paying a remediation company to do large amounts of mold remediation and air sealing.

Why Home Inspectors Report on Mold in Attics

Home inspectors will typically write up mold found in your attic.

This is because, as previously mentioned, mold that is not remedied will continue to grow and breakdown building materials.

Can It Stop You From Selling Your Home?


A home buyer may decide to not buy your home because of mold in your attic. While it is not the end of the world, you should try to have it fixed because it is a defect if the causes are still there.


Mold in your attic is not the biggest concern. It is caused by excessive moisture from air movement from humid air in your home, to a low humid attic with lower temperatures.

You should remedy this by air sealing areas in your attic: can lights, wall/drywall junctions, wall framing members, ductwork, bathroom vents, etc.

Air sealing can stop air movement into your attic which will prevent humid air entering a cold low humid attic space.

Before spending large amounts of money on air sealing and mold remediation by a company, I highly recommend hiring an independent home inspector to try to determine what the causes are and what the best course of action is.

I also, recommend reading my article on solar fans so you can truly make an educated decision.

Have a question? Comment below!