Can Too Much Insulation Cause Mold?

Insulating your home can be one of the best decisions of your life. After you start enjoying the benefits, the urge to increase the insulation kicks in. However, there’s a concern! Can too much insulation cause mold growth?

There are many areas in your home where mold can grow. Unfortunately, it’s almost impossible to ensure your home is completely “mold-free,” but we certainly wouldn’t want it growing over your insulation. Insulation is a solution to making your home mold-resistant, but before you proceed, let’s take time to find out: can too much insulation cause mold to grow?

How Does Mold Develop?

Before we talk about whether too much insulation can cause mold to grow, first, let’s understand how this thorn in the flesh of homeowners grows. Mold is microscopic in nature, living on organic matter, and thrives in warm and wet environments.

Mold spreads via spores, and it’s not a problem you can resolve completely. Mold might also grow on your insulation, but the conditions in the building facilitate that, not the insulation. It only needs three things to grow: mold spores, food sources, and moisture.

Mold spores are everywhere on earth, and anything that used to be alive can be a food source, so there’s nothing much you can do about those. Moisture is the only requirement you can control with adequate insulation. However, poor insulation installation will be like adding fuel to the fire instead of helping quell it!

Any temperature between 47 and 120 degrees Fahrenheit is favorable for mold growth. That means temperatures, even in most basements, can facilitate mold growth. It grows on fabrics, wood, and paper, meaning Rockwool and cellulose insulation materials are great hosts. Therefore, choose your insulation material wisely if mold is a concern.

Insulation: The Solution to Mold

If you are looking to prevent mold in your home, then you might need insulation. If installed correctly, the insulation will create dry-temperature conditions, and mold will be unheard of. However, if installed wrongly, it could lead to mold growth within the walls.

Insulation should block the source of moisture, thus acting as a defense against mold growth. However, not all insulation materials are perfect; therefore, you should choose the best insulation material available.

Fiberglass is a non-biodegradable material. The sharp ground glass punctures the mold before the spores attach. However, the paper backing on fiberglass is a mold food source. Cellulose insulation is made of ground paper. It’s an ideal food source when it gets wet. It should only be an option if you’re certain it will not get wet. We’ll discuss more of this later after tackling the too much insulation question.

Can Too Much Insulation Cause Mold?

It depends on whether you are using modern or old insulation materials. Most older homes were constructed with breathable materials, which allowed moisture inside. If you insulate with modern material without removing the older material, the latter will cause problems, including mold growth.

Ventilation plays a major role as well. For example, if you replace older windows with modern airtight ones, it’s obvious your home will suffer the consequences of lack of proper ventilation. Homes should have vents that release that regulate the air.

The Relationship Between Insulation and Ventilation

The South generally has longer summers and shorter winters. However, the winter months are colder, the outside is usually much cooler, and the windows are usually shut. The temperatures in and outside your home are roughly the same during summer. During this period, the uses of insulation and ventilation are not common.

Your home needs insulation and ventilation, and they must be balanced. Too much ventilation and too little insulation will make your home inefficient, especially in colder months, and bills will shoot through the roof.

Too little ventilation with too much insulation, on the other hand, will make your home stuffy and unpleasant. Your home will feel damp, and mold will likely grow. It’s, therefore, essential to balance insulation and ventilation without overdoing the other.

How Can Homeowners Control Moisture?

There are several measures every homeowner can take to control moisture and help curb mold growth. Water-logged materials, including insulation, should be removed and replaced. Sometimes water can move to unexpected areas which are hard to notice. Use dehumidifiers to reduce humidity in such areas.

You can also reduce the indoor humidity to 30 percent and vent the kitchen and bathroom outside rather than the attic. Carpets can absorb moisture and facilitate mold growth. It would be best if you avoided wall-to-wall carpets and instead use area rugs that are easier to wash.

Which is the Right Insulation for the Job?

Many homeowners are unaware that insulations come in different types, and not all can be used to remodel or build a new home. Also, your contractor might advise you on the most suitable insulation option within your budget instead of insulation that will keep you safe for years. We believe you deserve decades of comfort, good health, and a home with fewer mold problems. So, here are the most popular options currently.


Cellulose is a “blow-in” material made of recycled paper. It’s a great green choice because id biodegradable, and it might be one of your favorites if you care for the environment. Cellulose insulation is mostly used in attics and wall cavities because of its ability to occupy even the tiniest spaces and its efficient insulating capability.

Mold rarely affects cellulose insulation unless it comes to contact with water! The boric acid, used as a fire retardant, prevents mold growth. However, if the insulation gathers moisture, the effectiveness of boric acid will fade, and the material will turn into a food source. Once this happens, you cannot remove the mold completely, and you’ll need to remove the affected section.


Naturally, fiberglass does not allow mold growth because it’s not a food source. It contains tiny glasses that trap air and insulate your home. However, high amounts of air can move through fiberglass, and particles can be filtered out and serve as food sources for mold. Over time and with the right conditions, after facing resistance, mold can start growing uninterrupted.

To prevent a problem like this in the future, the contractor will suggest using another insulation material, such as cellulose, over fiberglass. It works if the application area is not the basement or crawlspace walls.

Fiberglass is also notorious for trapping moisture and leading to condensation problems. A good contractor knows that and will install the insulation with a vapor barrier. You will also need to take care of your fiberglass and ensure it doesn’t come in contact with water. Too much insulation of fiberglass will boost mold growth.

spray polyurethane foam for roof – technician spraying foam insulation using plural component gun for polyurethane foam, inside

Spray Foam

Unlike the insulation materials mentioned above, spray foam does not rust, rot, or deteriorate. That means the area sprayed with foam insulation will never be a food source of mold. Spray foam is highly water resistant and keeps dangerous moisture away. Closed-cell spray foam is far much better than the open-cell in blocking moisture.

Spray foam also creates an airtight seal that keeps allergens out of your home. For it to work, the contractor must install it properly. When water accumulates indoors and goes unnoticed and unaddressed, mold will find its final food source and start thriving. Spray foam is sturdy and crawls into every space when sprayed to provide an airtight seal.

Although installing spray foam seems costly, it’s a long-term solution that will save you money in the long run. Spray foam will last a lifetime when installed. The material is breathable and does not affect the natural ventilation of your home. Even though spray foam is the most convenient product, your home must be ventilated to prevent dampness.

The Issue of Too Much Insulation

If you are using spray foam, it will serve you for eternity. If you are using other options, you might need to replace or add layers to increase the R-value. We get it that most homeowners sit in the park pondering, “can I get enough insulation to protect my home and keep me comfortable while it reduces energy bills without breaking the bank for it, or should I spend my life savings on spray foam?”

Our best advice on insulation matters and where spray foam is involved is that cheap is expensive! If you use cellulose, you’ll have to add another layer to improve the already declining R-value sometime later. There comes the point when too much insulation turns back and starts to bite you financially, environmentally, and your home’s longevity.

Highly thermal insulation is indeed what you need in your home. No need to pile it on, because the first few layers do the heavy lifting. You end up wasting money in the process, and not just that. What the insulation was supposed to address becomes the problem it’s causing.

First, it’s the diminishing returns which means that the insulation is not as beneficial as you would want it to be, but you are losing money. Then there’s the environmental issue. By over-insulating, you waste materials. Does it sound right when natural resources and energy go to waste?

Then there’s the mold problem. Let’s say you put a layer over a layer from time to time. Moisture can get trapped in between, and mold can grow in those dark spaces. Besides, regulating the temperature in your home consistently may be closer to impossible. Before you realize it, the health issues kick in, and you finally make good use of your medical insurance.

It’s possible to over-insulate your home to the extent that it can’t breathe. What’s the worth if too much insulation can’t resolve the issue of mold growing in your house? The whole point is to prevent stagnant moisture. Besides, over-insulating will also mean the air in your house will be of lower quality.

Other Ways to Prevent Mold

Insulation works against mold, but it can’t prevent it entirely. As mentioned before, you can’t eliminate mold spores completely. No one would care so much if mold didn’t produce allergens and irritants and compromise our health. There has always been one mold prevention method – moisture control! Here’s how to deal with moisture in your home head-on.

Invest on Mold-killers

The CDC suggests cleaning your bathroom with products that kill mold. There are several options available in the store near you. However, if you prefer natural ways to get rid of mold spores in your home, baking soda, hydrogen peroxide, vinegar, and tea tree oil.

Clean and Repair the Gutters

Mold in the house could result from a roof leaking due to damaged gutters. Have your gutters inspected and cleaned regularly. Ask the contractor to check whether any water stains might indicate a leak.

Open Your Windows

Kitchens and bathrooms have the highest risk of developing mold. When taking a shower or preparing the family dinner or breakfast, open the windows to let the moisture flow out instead of building up in the house.

Check Out for Leaks

While household appliances such as your showers and kettles are the usual culprits, look beyond your bathroom and kitchen. Check your home thoroughly and see if any leaks or cracks would bring excess moisture where it’s not needed. If you find a leak, call the plumber right away.

Equip Your Home with Mold-Resistant Products

Use mold-resistant products like mold inhibitor paints or mold-resistant drywall. The latter is valuable in areas vulnerable to wetness, such as basements, laundry rooms, and kitchens. Traditional drywall is not mold resistant and can be expensive to replace after a mold attack. Modern mold-resistant drywall does not absorb moisture and therefore does not give room to mold growth.

Dry Wet Areas Immediately

Mold grows where there’s moisture, giving you time to fix the wetness before it attacks. If you notice wet places, a wet carpet, seepage into the basement after heavy rainfall, or leakage from a pipe, dry them within 48 hours.

Wrapping Up

Insulating your home is one of the smartest ways of preventing mold in your home. Too much insulation is not good. Mold might grow between the layers, depending on your insulation material of choice. Sooner or later, you might be forced to bring the whole thing down, costing you more!

Spray foam insulation is becoming a popular choice for wet areas because of its great insulation properties. Spray foam is also impervious to moisture. Talk to us if you want to install high-quality insulation in your Georgia home. We are just a call away.

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