Can Mold Grow On Spray Foam Insulation?

Jessica Stone
by Jessica Stone

You likely understand by now all of the dangers that are associated with mold growth in the home. They can present health hazards that cause issues as minor as enhanced allergy symptoms or as serious as major lung damage. Aside from the health risks for home occupants, elimination and remediation of mold can be costly and very overwhelming.

Moisture accumulation is the key factor that leads to mold and mildew growth. Your best defense against moisture is prevention and this means creating an airtight seal in your attic, basement and other areas of the home.

Sealing off a space will rob mold spores of their comfortable environment to live, grow and multiply. Spray foam insulation is the best product on the market for completely closing up a space to prevent moisture. However, you may be wondering, “can mold grow on spray foam insulation?” Mold cannot grow on spray foam insulation because it is water resistant and unlike metal or wood, it doesn’t rust, rot or deteriorate.

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Signs of Mold in Your Home

The first step in mold prevention in the home is knowing all of the possible signs that it exists. Sometimes detection is as easy as noticing must odors, green or black spots on the walls or as complex effects on your own body.

If your home has a consistent stale, musty odor, this is a good indication that mold is hiding somewhere. However, the most common signs of mold are the ones that occur in your body. If you have mold growing in your home, it’ll be hard to avoid inhaling it. The symptoms associated with mold inhalation will often appear like allergy symptoms such as sneezing or coughing.

In some cases, you may experience lightheadedness or confusion when you’re breathing in mold. Never ignore any changes that your body may be trying to tell you. Schedule a visit to your doctor and they will be able to diagnose the signs of mold inhalation. Additionally, a mold expert can come out to your home, identify and locate the source of the problem.

What Causes Mold in the Home?

Most often, the reason for mold suddenly appearing in the home has to do with water damage. This could be related to a burst pipe or flooding in an area of the house. Regardless, moisture is a major concern and should be taken seriously. While it’s very easy to repaint a discolored ceiling, it may have deeper structural damage that could lead to more serious issues down the road.

For mold to grow, it needs moisture, a warm climate and some type of biodegradable material to feed off of. If you haven’t experienced a burst pipe or flooding recently, the issue may lie in your attic. More specifically, your attic may have been improperly or insufficiently insulated.

An attic that is properly insulated will successfully keep moisture out and cool air in. However, any gaps that exist in the insulation will allow for humid air to enter and result in the ideal breeding ground for mold to form.

Additionally, your HVAC system can cause your minor moisture problem to become a major mold issue. If you have mold hiding in your attic or walls, mold spores can seep into your HVAC system. They will then travel through the pipes and continue growing and spreading throughout your entire home.

What is Spray Foam Insulation?

Spray foam insulation is a type of insulation and air-tight barrier material that is used to seal floors, walls, and ceiling cavities against airflow. It is commonly used in the home and commercially around electrical outlets, light fixtures, and where walls meet doors and windows. Spray foam can be applied to an open cavity, such as in crawl spaces, attics, rim joists, and in new construction.

The product can also be used in pole barns, commercial settings, and existing homes. So long as the cavities are open and easily accessible, spray foam can be applied. Unlike traditional insulation, spray foam does not lose its shape, and effectively seals gaps, cracks, and crevices upon installation. It also will not settle, sag, or compress as time goes on.

There are two main forms of spray foam insulation: open cell and closed cell.

  • Open cell spray foam insulation is applied by spraying into open cavities in a structure, creating an air seal and continuous insulation. It is light, pliable, and can expand up to 100 times in size to fill every little crack and crevice. With this type of spray foam insulation, water can move through but does not soak it up. Water is the blowing agent for open cell spray foam and this product also helps with sound dampening,
  • Closed cell spray foam insulation, on the other hand, is a spray-applied plastic that also creates an air seal, provides continuous insulation, and is applied to open cavities. In most cases, this product is not recommended for homes, but there are some instances where it may be more suitable than open cell. Though, it is more commonly used in commercial structures, vans, and pole barns. Unlike open cell, closed cell spray foam doesn’t have a high expansion rate, is not water permeable, is dense, has a chemical blowing agent, and is best used for smaller projects.

Regardless, both types of spray foam insulation limit air leakage wherever they are applied.

Can Mold Grow on Spray Foam Insulation?

In short, mold cannot grow on spray foam insulation. Unlike materials like wood and metal, spray foam does not rot, rust, or deteriorate. It is also water resistant.

With these attributes, spray foam can actually be used on currently developing mold patches, as it has been proven to hinder growth and prevent additional spread. The spray foam insulation does this by cutting off both the mold’s air and moisture supply.

Though, there are instances where mold may be found around spray foam insulation that are not directly related to the spray foam itself (more on this below).

Using Spray Foam Insulation to Prevent Mold

In terms of counteracting moisture in your home, sealing up your attic is most likely the most important step. Spray foam insulation, sometimes referred to as polyurethane spray foam, is the only product on the market that will successfully and completely seal off an area.

This product is specially designed not to attract mold and unlike other materials, it does not rot, corrode or deteriorate over time. When you use spray foam insulation properly, the area will never become a source of food or hospitable environment for mold to grow.

Spray foam’s water resistance will keep moisture and humidity where it belongs: outside of your home. Its ability to form an air tight seal will also keep allergens and outside air from entering into your home. Subsequently, the fresh air provided by your HVAC system will stay inside, effectively reducing your utility bills.

However, keep in mind that proper insulation is only part of the solution to mold. You’ll also want to ensure that your home has appropriate ventilation to avert moisture accumulation through air circulation.

Factors that Could Encourage Mold Growth Around Spray Foam Insulation

The key to stopping mold is to a perfect balance between airtightness and air circulation. While the design of spray foam insulation does not conduct mold growth, it’s important that it’s installed correctly. In some cases, mold may be found on or near spray foam insulation in the following is present:

  • Gaps in spray foam insulation. If the spray foam insulation was applied haphazardly, this could lead to holes, gaps and even air leaks. The air movement through these gaps can most certainly allow moisture to form and invite mold growth.
  • When moisture is present. This relates back to ensuring that the product is properly installed. You would not have this issue if you’ve successfully created an airtight seal.
  • Mold needs organic material to grow. In addition to moisture and warmth, mold requires organic material to grow and feed on. If mold is growing near spray foam insulation, there may be household dust particles. Fabric fibers and skin cells are enough food sources to initiate mold growth.
  • A more significant mold reservoir already exists. If mold exists on or near spray foam insulation, this may be due to the fact that there was already a high level of mold in the home to begin with. High levels of mold spores can often be traced back to moldy fiberglass insulation or building reservoir.

Additional Measures to Prevent Mold

Although spray foam insulation can be a great tool to combat mold, there are additional measures you should take to keep your attic spaces mold-free:

  • Inspect regularly for roof leaks. Leaks in your roof can produce moisture in your attic. To locate possible leaks, look out for discoloration on wood or insulation, as this is usually a sign of water damage. Pay close attention to the areas where two roofs join at an angle – this spot is especially prone to leaks and cracks. The area that surrounds plumbing stacks can also suffer from water infiltration.
  • Ensure sufficient insulation. Attic insulation is crucial to controlling temperature and limiting moisture in the space, effectively preventing mold growth. In winter months, the temperature in your attic should be close to that of the outside air. When your attic is appropriately insulated, the air transfer between the attic and your living area is minimized. Make sure that you have enough insulation in your attic and also that it is in good shape.
  • Ensure adequate ventilation. With sufficient ventilation, moisture levels in your attic will rise. This is especially important in winter when warm air rises, enters the attic, and condenses on cold exteriors. Adequate ventilation will allow the moisture to escape from your attic and thwart mold. Also, make sure that your vents are not covered up by insulation.
  • Vent appliances outdoors. All of your vents, kitchen, dryer, and bathroom included, should be vented directly outside instead of into the attic. Otherwise, your ventilation system may become overwhelmed and no longer be able to function properly at removing moisture.

Final Thoughts

The best way to stop mold before it starts is to keep moisture out of your home and your attic. Spray foam is one of the greatest allies you can have against fighting moisture, as mold cannot grow on it. This, along with other preventative measures, will allow you to effectively create an environment that is unsuitable for mold to even grow in the first place.

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Relevant Questions

What is the R-value for spray foam insulation?

When it comes to closed-cell sprayed in foam insulation, the R-value can range from R-4.9 to R-7.1 per inch. Closed-cell insulation materials such as Icynene ProSeal, can allow you to reach R-21 with a three-inch layer.

How long does spray foam insulation last?

With the proper installation, spray foam insulation can last you the entire lifespan of your home. Foam insulation adheres very well to typically any surface and will preserve its firmness when dry.

How long does spray foam insulation take to dry?

After applying spray foam insulation, it will generally take anywhere from five minutes to an hour for it to become tack-free. However, it will take around 8 to 24 hours for spray foam insulation to cure completely depending on the particular product and installation site’s conditions.

If you want to speed up the process, misting the area you’re applying it can increase dry time. Ironically enough, spray foam insulation needs moisture in order to expand.

Are there any health concerns associated with spray foam insulation?

According to the Environmental Protection Agency, people who become exposed to the chemicals in spray foam, whether it be through dust, vapors or aerosols, may run the risk of developing certain health issues. If you don’t wear the proper protection gear, you could develop asthma, lung damage, sensitization, skin and eye irritation or other breathing and respiratory concerns.

Jessica Stone
Jessica Stone

Jessica considers herself a home improvement and design enthusiast. She grew up surrounded by constant home improvement projects and owes most of what she knows to helping her dad renovate her childhood home. Being a Los Angeles resident, Jessica spends a lot of her time looking for her next DIY project and sharing her love for home design.

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