Can You Leave Insulation Exposed In The Garage?

Whether you are buying a new house, or exploring the deeper regions of your garage, you’ll likely find some strange, fluffy pink stuff on the walls. Though this insulation is usually covered with walls, many times it’s not; and people rightfully ask if it’s safe or not for this insulation to be exposed in garages.

Insulation should not be exposed in the garage if possible. Exposed insulation can cause coughing, itching, general irritation, and can even get in your eyes or lungs. While it’s best if all rooms with insulation be covered, the occupied areas are the priority.

But, because there are different types of insulation, there are other factors that have to be considered for a thorough decision. Some types are worse to leave uncovered, and some are better. Below we will go over the different types of insulation, and some other related topics.

Which Types of Insulation Can I Leave Exposed in a Garage?

There are four primary types of insulation used in garages and attics. Let’s go over each type and explore its level of safety.

1. Fiberglass

By far the most common insulation used to date, fiberglass is insulation threaded with silicon or glass for their heat-resistant properties. It has an average R rating (R rating is the effectiveness of insulation resistance, the higher the number the more the resistance) of 3.1.

Fiberglass is considered to be nontoxic. However, because of the microfibers from the insulation and the glass particles that can easily spread, fiberglass does tend to irritate the skin, throat, and eyes, if exposed. It can lead to more serious issues if exposure is consistent. 

If you’re not going into the garage very often — say you park on the street — then the fiberglass is definitely not going to kill. But, it is still a good idea to cover it regardless in order to ensure the avoidance of potential problems. But, for high traffic areas, covering fiberglass is a must. 

2. Cellulose

Made from around 80% recycled paper materials, cellulose offers natural and effective resistance. R is 3.1. Though it is made up mostly of paper, a lot of the other 20% includes chemicals, fire retardant among them. Because of the presence of the chemicals, in addition to the other microfibers of dust and paper that can cause irritation, it’s best to put a barrier between you and your cellulose. 

3. Mineral Wool

Typically made from slag stone, mineral wool, like fiberglass, weaves together ground up pieces of heat-resistant metals that provide insulation. R is 3.7. Like fiberglass, mineral wool is considered to be nontoxic. But, with the microfibers posing a risk for health problems, it faces the same issue as fiberglass and cellulose do. So cover your mineral wool up too, if you can.

4. Foam

The two customary types of foam insulation — Polyurethane (R 6.3) and Polystyrene (R 4) —  are highly versatile and highly effective means for insulation. Polyurethane is a sprayable foam made by a reaction of two chemical agents, and Polystyrene is a solid that strongly resembles Styrofoam.

Polyurethane comes in two forms: open and closed-cell foams. Open-cell foam is softer and allows some air in, while closed-cell foam is harder and lets no air in. It is not safe to leave Polyurethane exposed with risks of asthma, irritation to the skin and eyes, and even long term health damage being possibilities. 

The highest risk for negative effects will occur in the first few days after the foam has been sprayed. But, even after that, because of some of the chemicals present, it is not a good idea to leave the foam exposed. Furthermore, the foam can be highly flammable so it should have at least something covering it.

Polystyrene is made in factories that deal with chemicals that can be dangerous on their own, but the foam itself doesn’t appear to be toxic once it is formed or in a wall. However, because of its combustible properties, fire-retardant is often added to the foam, which has been criticized for its carcinogenic properties. Here is a short article about fire retardants sourced from an actual firefighter.  

So, whether you are using regular foam with or without the fire retardant, you should cover it up. Either the foam will be highly flammable, or it will be potentially highly toxic.

What Should I Cover The Insulation in My Garage With?

Walls as we know them are largely constructed of drywall. Drywall is the primary material used to cover insulation. It’s also safe and has a respectable amount of fire-resistance.

Foil faced insulation is another common material used to cover insulation. It is traditionally used with fiberglass batts (the pink roles). It is an extremely effective insulator, but it often has backing — made of paper — that can be a fire hazard.

Some are curious if plastic can be a good covering for insulation. If you are doing a weekend renovation, like painting the non-exposed walls in a garage, and need to cover the insulation up, then plastic can be fine. But long term, moisture can get trapped between the plastic and the insulation, which can produce mold.

Sometimes home renovations are just not possible during a given period due to lack of resources or time. But, in the meantime, at least take the necessary precautions so that you and your loved ones can be safe. 

If someone in your house sleeps in a room with exposed insulation, consider moving them out until you can cover it with drywall or foil. Otherwise, if others don’t often occupy the exposed areas often, then your project can wait a bit. But don’t wait forever.

Can Insulation Get Moldy?

Whether a pipe bursts and causes a flood in your home or you just live in a rainy city, mold can be a serious concern. Insulation, being connected to the skeleton of the house, raises concerns about mold even more. As you might expect, some types of insulation can get moldy.

Fiberglass on its own is both water-resistant and mold resistant. If you elect to have backing on your fiberglass, then it can be a source for mold to grow on. It should be fine unless the backing gets wet, however. But, covered or not covered, if the fiberglass is just by itself, mold should not be a concern. 

Because cellulose is mostly made of paper, it can be a huge source of mold. Make sure that wherever your cellulose is exposed —  whether it’s in the garage, attic, or rooms —  that there aren’t cracks in the roof or the walls to ensure maximum dryness, and cover it whenever you can. 

Mineral wool is even more water-resistant than fiberglass is, so whether it’s open to airflow or closed by a wall, there shouldn’t be any mold on it.

Both open-cell and closed-cell polyurethane are water-resistant, but open-cell foam — being softer — is not entirely waterproof. Some damage can occur if water is exposed to open-cell foam, but mold doesn’t grow on the foam itself. Closed-cell foam is closer to being completely waterproof and is the better option exclusively from the perspective of water damage. It shouldn’t get mold either.  

Polystyrene is not entirely waterproof, but it is water-resistant and appears to always dry out even if exposed to water. You should be safe from mold here too.