Does Spray Foam Insulation Cause Mold?(No! See why)

Does Spray Foam Insulation Cause Mold?

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Does Spray Foam Insulation Cause Mold?

Spray foam insulation is a type of insulation that has been gaining popularity in the last few years.

It comes as little beads mixed with air and then sprayed onto your walls to fill any voids or gaps where heat may escape from.

You can use spray foam insulation anywhere you have an opening, whether it’s on the outside of your house, between two layers of drywall, or even over a window.

Spray foam insulation can be used to insulate any gap or void, as long as the gap is not over three feet wide.

For gaps wider than three feet, consider using rigid foam panels instead of spray insulation.

Also, if you are looking to insulate a wall cavity between two wall studs.

remember that this type of application requires an additional layer of drywall against each wall’s flat surface for the walls to be fireproof and vapor-permeable.

Otherwise, you will need to install mesh netting first before applying the spray foam insulation.

Does Spray Foam Insulation Cause Mold?

No! Spray foam insulation rarely increases the risk of mold growth but reduces it. Spray foam insulation opens the surface to water vapor movement.

Still, the vapor barriers in modern construction prevent this moisture from reaching the structure’s interior and thus do not increase the risk for mold growth.

The popular method increases ventilation during installation, especially when working on roofs with no extra ventilation after installation.

Does Spray Foam Insulation Cause Rot?

No! Spray foam does not cause rot. This is because it doesn’t contain any moisture. Thus, there’s nothing for the bacteria to feed on.

Still, if you have rotting wood beams or walls, then adding spray insulation will only speed up the process of deterioration.

This is because it seals off these areas from fresh air circulation. Therefore, I recommend having your house inspected before installing spray-foam insulation.

This is in case you have a moisture problem somewhere in the walls.

If you have a moisture problem, hire a professional to identify and fix it before turning to spray insulation.

Rotting wood beams under rooflines are called “sag” beams.

They sag down between rafters, which can cause problems when installing new roofs since there’s nothing to attach them to.

To help prevent the rotting of wood beams by water:

I recommend you attach 2×4 crosspieces across these beams perpendicular to the floor joists below using steel plates and screws at every 16 inches – two per beam.

These 2×4 crosspieces will support the beams, preventing them from sagging down between rafters and making it easier for you to attach new roofing material.

I also recommend increasing ventilation in your attic by removing existing insulation where possible (and adding more insulation underneath the rafters).

This will allow air circulation between your roofline and your attic, which can help prevent rot caused by water penetration into your roofline.

Spray foam provides an excellent way of sealing this area from moisture.

This is because it blocks airflow from penetrating through any cracks or penetrations in areas such as plumbing vent pipes and electrical outlets.

Allowing less opportunity for mold growth.

Spray foam is a brilliant choice for many building insulations, unlike fiberglass, because it’s a closed-cell foam that forms a permanent airtight seal.

Making it an excellent choice for high moisture areas such as bathrooms and kitchens, and exterior walls.

What Happens When Spray Foam Insulation Gets Wet?

Some things happen when this type of insulation gets wet. One thing that happens is the air barrier still works, but nothing else does.

As a result, any space or building envelope component that needs to drain well cannot. This means leaks and rot.

When removing this type of insulation, wear a respirator and gloves. The respirator is to protect you from any chemicals that might be under the insulation.

The gloves are to protect you from the resin, which contains a hardening agent known as methylene diphenyl di-isocyanate or MDI for short.

It isn’t clear because it stands for methylene Dicyclohexyl Diisocyante, but it’s easier to refer to as MDI.

This chemical can cause asthma-like symptoms or even anaphylactic shock in those who have allergies/sensitivities to it.

If you’re removing spray foam as part of your job, wear a good quality respirator and disposable clothes if possible.

The material is sticky from the moment it’s applied. If you need to remove this type of insulation from a vertical surface, use a disposable plastic putty knife instead of metal.

If your spray foam insulation gets wet, don’t panic.

Suppose you have an area that has been well sprayed with the right amount of chemicals and use a proper spraying method.

In that case, it should not be a problem getting rid of the excess water and drying everything out as expected.

You’ll want to hose off any areas soaked in water or completely saturated/soaked in any other liquid (like urine).

Rinse off the entire area – up high and down low – before turning your attention to any areas that might be water damaged.

If you sprayed the insulation well and took care of any excess liquid as soon as possible, this insulation should remain viable and last for many years to come.

It will not lose its insulating properties.

Still, if moisture goes too long without you removing it from spray foam insulation, those chemicals will break down, and their performance will degrade.

This is one reason it’s important never to seal or cover up spray foam insulation completely.

The idea is always to let any water escape instead of trapping it inside to damage other building components.

Will Spray Foam Insulation Stop Water Leaks?

It is ideal for sealing moisture and water vapor. Some types of foam insulation have a closed-cell structure that resists moisture penetration.

An example is Polyurethane and XPS (polyisocyanurate). Allowing too much moisture into an insulated space can be as disastrous as not having enough insulation in the first place.

Thus it is important to choose wisely when choosing to spray foam insulation for your project.

Spray Foam Insulation has proven itself to be one of the most cost-effective energy solutions available on the market today.

It can seal out air infiltration through any building envelope assembly while providing superior thermal performance compared to other assemblies.

Spray foam insulation is a modern way to stop air infiltration and loss and the resulting energy loss.

This means that you can reduce your heating costs in winter and lower your cooling costs in summer.

In short, spray foam insulation offers a more efficient home with greater comfort at an affordable price.

Spray Foam Insulation has been in use for many years by contractors.

Still, homeowners are also using it because of its high R-value, low permeability, and effectiveness in stopping thermal transfer.

Contractors use closed cell spray foam because of the way it adheres to structural elements.

It clings to wood or metal studs, so building walls stay strong under pressure from earthquakes or extreme conditions like tornadoes or hurricanes.

Closed-cell spray foam can also act as an air barrier between different parts of your home.

Closed-cell insulation is usually denser than standard open-cell insulation, so it has a much higher R-value.

This means that spray foam insulates better. This is because fewer air pockets make it more effective in keeping out heat and cold.

Open-cell insulation is the cheaper option for insulating walls or roofs because it’s less dense, but it doesn’t offer the same level of thermal protection that closed-cell does.

Still, there are three things to keep in mind when using closed cell spray foam insulation:

Make sure you use waterproof membranes around penetrations like windows and doors to prevent water from getting inside.

Keep humidity levels low to prevent mold growth.

Keep the spray foam away from any metal materials, as it will erode them.

Spray foam insulation has been for commercial or industrial purposes because of its high price.

It wasn’t affordable for most homeowners until recently, when new technologies made it possible to bring it to the masses at a much lower cost.

Best practices call for spraying closed cell insulation on walls and using open-cell spray foam on roofs and ceilings.

The reason is that open-cell allow moisture vapor to escape through tiny pores in the material.

This can reduce the chances of mold growth and open up greater risk of water damage if any occurs.

Does Spray Foam Insulation Shrink Over Time?

Yes! If you cut open a piece of spray foam insulation, the cells are always closed or almost closed.

This reduces the risk of moisture entering the product and is part of sealing out drafts. It also prevents the formation of mold.

If you live in an area with cold weather for several months, you may notice that there is more space between each cell.

The reason behind this is that heat causes polymer materials like polyurethane foam to expand, not shrink.

When there is less heat throughout the year, your spray foam won’t be expanding as much.

Thus, will have shrunk by comparison to when it was first installed after its heated from all sides during installation to its viscosity similar to honey.

Thus, it is always important to insulate your attic, no matter what type of insulation you use.

If the insulation doesn’t cover all areas, some parts will be warmer than others and cause shrinkage over time compared to these colder areas.

Can You Leave Spray Foam Insulation Exposed?

No. It’s not a good idea to leave spray foam insulation exposed. You don’t need to cover Spray foam with drywall or any other finish material.

Still, it should always have some protective covering over the raw foam. This could include drywall, plywood, metal lathe, fiberglass, etc., depending on what you will use it for.

Suppose you build a storage shed or storm shelter where the insulation will never contact moisture or water damage.

In that case, you can use a skinned-over layer of open-cell foam as your exterior siding and lighting fixture enclosure cover.

Open-cell foams provide little protection from water damage and would absorb liquids. Making them ideal as exterior siding.

A better choice would be to use closed cell spray foam insulation for this type of project.

Or you can use constructed panels made with wood or metal lathe to cover the raw sprayed polyurethane material.

Open-cell foams are not very durable and damage easily. Especially when they come in contact with various types of chemicals, oils, weather extremes (wind, rain, snow), etc.

A small amount of open-cell foam is most likely present in most types of spray-on insulation materials.

This helps reduce costs when mixing up batches at the factory and speeds up the curing process.

This is when installing them on walls so workers can get back out into the homes more quickly. Open-cell foam is not needed in all applications, but it helps reduce material costs.

Open-cell foam is often used as an air barrier since you can tackle it into place quickly.

They will not allow water vapor (humidity) to pass through this layer than other types of insulation materials would.

Placing or hanging sheets of 5/8 drywall over spray foam insulation boards is not a good idea because the weight of this type of paneling could easily cause large sections to fall off.

This can cause damage to the side or structures below it. One sheet should always be fully supported by furring strips, plywood lathe.

Some other type of reinforcing material placed on top instead of directly hanging them from open-cell sprayed polyurethane board insulation.


Spray foam insulation is a great way to stop water leaks, keep your home warm in the winter and cool in the summer.

It also never needs painting or staining. There are many myths about spray foam that seem scary but can be easily debunked with simple research.

For example, one myth related to mold growth is that if you have an area of wetness on your drywall from leaky pipes.

This causes mold problems when it’s covered up by new insulation sprayed over the top.


Hi! I I faced many questions from customers about different products, and there was hardly any help on the internet. After learning all the things about these products as a manager the hard way, I decided to start a blog and help other people.

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