Mold is bad news, regardless of where it is in your home. Unfortunately, spray foam insulation can also be affected by mold if not installed correctly. If you find mold on spray foam insulation, you must act quickly.

Start by removing any loose mold visible on the surface of the spray foam insulation. Be sure to wear gloves and a mask to protect yourself. Then, vacuum up any remaining dust or debris with a HEPA-filtered vacuum cleaner.

[Important!] If the mold is dark in color, contact a professional mold remediator. A simple nuisance mask won’t protect someone from brown or black mold spores that become airborne.

While it may sound simple, the process isn’t as straightforward in most cases. Below, we look at some tips to help you handle the issue.

Is Mold Dangerous?

Yes, mold is potentially dangerous, especially in cases where it is not noticed or properly taken care of. Mold can cause various health issues, ranging from respiratory problems to skin irritation.

In some cases, it can even be toxic if the species of mold is particularly hazardous. In addition, mold spores can result in allergy symptoms, including sneezing, wheezing, runny nose, watery eyes, fatigue, headache, and difficulty breathing.

Prolonged exposure to mold can even lead to more serious health issues, such as asthma and other respiratory illnesses. If someone in your home suffers from any of these conditions, it is best to take extra precautions when dealing with mold.

How to Tell If You’re Dealing with Mold?

There are a few telltale signs that you may be dealing with mold. Visible mold growth is the most obvious sign, but there are other ways to tell if your home has mold growth.

  • Rotten Smell: If your insulation has a musty or rotting smell, this could be an indicator of mold growth.
  • Dampness: When spray foam curates, it is no longer wet. Therefore, any dampness in the insulation could be a sign of a mold problem.
  • Visible Discoloration: If the insulation has discoloration, such as brown or black spots, this could be a sign that mold is present.

Some common types of molds that grow around spray foam insulation are Cladosporium, Penicillium, and Aspergillus. The characteristic features of these molds are musty odors and dark patches. As for color, the mold can be black, white, yellow, green, and almost any other color in between. 

Typically, spray foam insulation does not foster mold growth. However, if it’s not properly sprayed, there’s a chance that mold can develop. Thus, you should look at the areas around the insulation for signs of potential mold growth.

Can Mold Grow On Spray Foam (itself)?

Mold usually does not grow on spray foam but can grow on the underlying surface or surrounding area. Spray foam does not attract mold, nor does it provide any nutritional value for mold spores, insects, and other pests.

If the insulation is not given enough time to cure and dry, this can lead to mold growth. Other causes of mold on spray foam insulation include water damage, condensation, and inadequate ventilation.

I Have Mold On Spray Foam, What Are The Possible Reasons?

There are plenty of reasons why you may have mold on your spray foam insulation. Here are some of them.

Poor Application

When applying spray foam, you must cover all seams and cracks. If you leave areas exposed, moisture can seep in, leading to mold growth. Also, if the spray foam is applied too thick in one area, it can trap moisture and cause mold.

Improper Ventilation

Mold needs a damp environment to grow. If your home has poor ventilation, moisture can easily build up in the air and create an ideal environment for mold.

Leaky Pipes

A leaky pipe can cause water to seep into your walls and insulation. As a result, the surface becomes a breeding ground for mold.

Accumulated Dust

Dust particles can accumulate in spray foam insulation, which creates a food source for mold spores to grow and multiply. Keep in mind that spray foam is of no nutritional value for mold.

So, if you see mold around your insulation, it’s likely due to the presence of another food source. Besides dust, pest waste, paper backing, and dirt can also act as a food source for mold.

High Humidity

If your home has high humidity levels, it can cause condensation to form on your insulation, creating the perfect environment for mold growth.

Inadequate Insulation Removal

When removing old spray foam insulation, you must ensure that all traces of it are removed. If a section is left behind, mold can grow in the area.

Suppose you previously had fiberglass insulation, which is prone to mold growth under the right conditions. Modern fiberglass insulation is ‘faced’ or covered with a paper product, which has nutritional value for mold.

Let’s say when replacing fiberglass insulation with spray foam; you do not properly remove the paper backing. So, any mold spores present in the old insulation can start to grow again when exposed to moisture and air.

How to Deal With Mold Growth on Spray Foam Insulation?

The ultimate solution for these problems is mold removal. A bleach solution with nine parts water and 1 part bleach can be used to remove the mold. However, if the problem persists, you should consider an air quality test by a professional. It will help you identify the root cause of the mold and develop a solution.

If the problem has spread too far, get a mold removal company on board. You might be able to scrape off the visible mold, but it’s likely the spores are still in your house. They will eventually start to spread again. Professional mold removal companies are trained to take the necessary precautions and safely dispose of all infected materials.

The final resort is to replace the insulation. Get rid of your existing insulation, remove the mold from the underlying surface, treat the root cause of mold growth, and then replace the insulation with a new one.

Tips to Prevent Mold

The best way to deal with mold is to prevent it in the first place. Here are some tips to help you keep your spray foam insulation free from mold:

  • When applying spray foam, cover every crack that may allow moisture to seep in. It includes the crevices around windows, doors, and other openings.
  • Check for leaks and seal any gaps or cracks in the walls.
  • Install proper ventilation to reduce moisture levels in your home.
  • Keep the area clean and free from dust and dirt, as these can act as food sources for mold spores.
  • Keep the humidity levels in your home low by using air conditioning, dehumidifiers, and fans.

While DIY insulation might save you some labor costs initially, poor installation might end up costing you more in the long run. Getting a professional to install your insulation is always a better option if you want to ensure proper installation and mold prevention.

Do Other Insulation Options Resist Mold Better?

Most insulations resist mold. Some of the more popular options are fiberglass and cellulose insulation.

Cellulose Insulation

Cellulose insulation contains boric acid, which is added to make the material a fire retardant. Fortunately, boric acid is also a natural mold inhibitor.

Therefore, cellulose insulation is one of the best options against mold growth. Additionally, it helps reduce energy costs and increases soundproofing capacity.

Fiberglass Insulation

Fiberglass insulation is made from recycled glass and does not provide a food source for mold. As long as the insulation is properly installed and well-sealed, it should prevent mold growth.

However, it’s hard to say if it resists mold better than spray foam insulation. Like spray foam, if fiberglass insulation is not applied correctly, it can create a breeding ground for mold.


Evan has decades of experience as a project manager for large-scale commercial renovation home-building projects throughout the US. Currently, Evan runs a successful construction management company in Virginia.

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