Is Insulation Flammable? (Different Materials)

When choosing insulation, the most typical things to consider are the R-value and the prevailing weather conditions where you stay. But how about the flammability of the insulation and the consequent safety hazards? Do insulation catch fire?

Not all insulation materials are flammable. Fiberglass insulation and mineral wool are relatively fireproof. But while they may not immediately catch fire on exposure to extreme heat, they melt eventually. Nonetheless, other insulation materials like cellulose, PIR, and Styrofoam are far more flammable.

What makes each of these insulation flammable or fireproof? What are the consequent security hazards, and what can you do to protect your home from flammable insulation?

Is Blown-in Fiberglass Insulation Flammable?

Fiberglass insulation fundamentally doesn’t catch fire. From its inherent design, fiberglass is built to withstand extreme temperatures.

That said, kraft paper backings integrated into fiberglass insulation to act as vapor barriers are inflammable.

But such flammability is suppressed when the fiberglass manufacturer equips such kraft paper backings with foils that resist fire.

Nevertheless, never overrate the non-flammability of fiberglass. There is a threshold of heat exposure at which fiberglass begins to melt.

Specifically, when fiberglass insulation is directly exposed to extreme temperatures beyond 1,000 degrees Fahrenheit, it begins to melt.

But why should you worry about such melting?

When fiberglass melts, it disperses heat. This is because the melting process of fiberglass involves the release of oxygen. Such gases fuel ignition.

Now, if there are flammable materials in the surrounding, there is a high propensity for such materials to catch fire.

Is Cellulose Insulation Flammable?

Cellulose, being made from recycled paper fiber, holds the award for the most environmentally-friendly insulation material.

So if you are keen on the ecological compatibility of your insulation, you are fine with cellulose. But if non-flammability is a core requirement, you should steer clear of cellulose insulation.

Made from recycled paper, cellulose insulation is naturally flammable. It quickly catches fine, aggravates the flames, and burns up quickly.

Most cellulose insulation is intensively treated with fire retardants. But this doesn’t do much when cellulose is sustainably exposed to thick flames.

It is worth noting that Consumer Product Safety Commission classifies cellulose as a fire hazard and advocates for caution with cellulose insulation in fire-prone environments.

Is PIR Insulation Flammable?

For those who don’t know, PIR is a shortened form of polyisocyanurate. PIR insulation is reputed for its spectacular thermal efficiency.

Its stability –regarding its fixed dimension in the long term – and its energy efficiency make them excellent insulation materials.

However, PIR is made of complex hydrocarbons. This makes it inevitably prone to catching fire. Deploying PIR insulation in fire-prone buildings is highly discouraged.

Such a high propensity to combustion explains why it is unwise to deploy PIR insulation in renovating buildings damaged by fire.

Is Styrofoam Insulation Flammable?

Styrofoam generally refers to extruded polystyrene foam. The latter is better known as Blue Board.

Here is an interesting fact about Styrofoam. It doesn’t decompose. But despite its non-biodegradability, Styrofoam is very combustible.

If the temperature rises to 212 degrees Fahrenheit, you can expect your Styrofoam insulation to start melting.

If the temperature goes further to 680 degrees Fahrenheit, you could see your Styrofoam emitting sparks. But by 800 degrees Fahrenheit, your Styrofoam will catch fire almost on its own.

Is Foam Insulation Flammable?

Foam insulation is not as flammable as cellulose insulation, but it does still catch fire if exposed to substantial heat for long.

The flammability of foam insulation, particularly the spray foam variant, can be traced to its characteristic nature as a plastic.

Spray foam combines plastic materials chosen for their capabilities to hold off air and consequently thermally insulate where they are deployed.

But plastics – typical of spray foam – are great fuels, almost sharing combustibility with wood and leather.

However, specially treated foam insulation can hold off fire for a while. This is specific to foam insulation products with a class 1 fire rating.

Such foam insulation can resist standard fire – upon exposure – for at least 60 minutes. For this time, it will not spread the fire, acting as a buffer for this interval before giving in after an hour.

Is Foam Pipe Insulation Flammable?

Foam pipe insulation is increasingly adopted for insulating residential properties for its affordability and ease of installation. Neoprene and polyethylene count among the top foam pipe installation in such deployments.

Neoprene and polyethylene are flammable. Some foam pipe insulation is treated with materials that cause the fire to eventually go off on its own after the fire source is removed.

When installing foam pipe insulation, keep them at a minimum 6 inches distance from a single-wall flue connector.

The only instance where such a recommendation can be voided is when the manufacturer states explicitly so.

What Insulation is Not Flammable?

Not all types of insulation are flammable. Other than fiberglass, which holds its own against fire, fibrous mats and mineral wool have impressive fire resistance.

Let us talk about them.

Fibrous Mats

Fibrous mats are decomposable fibrous woven mats. This is commonly made of coconut fiber, with the thickness and size varying to the intended application.

Fibrous mats boast remarkable resistance to fire. Generally referred to as asbestos, fibrous mats not only resist fire, they don’t conduct electricity either.

This means there are zero risks of your fibrous mat insulation lighting up in situations of electric circuit malfunctions.

That said, fibrous glass is not infinitely fireproof. When this insulation material is exposed to heat exceeding 3,000 degrees, its fire resistance can break down.

Glass Wool

Glass wool – sometimes referred to as mineral wool or rock wool – is made from basalt.

Rock wool is gaining popularity among homeowners in the United States as a choice of insulation material for its thermal efficiency, sound, and fire resistance.

With R-values going as high as R-3.5, glass wool doesn’t easily catch fire. Rock wool is specially designed to decelerate the transmission of fire by localizing the fire. Its fibers are reasonably fireproof.

When properly installed, Rockwool insulation can withstand temperatures north of 1,000°C without catching fire. This explains why construction engineers prefer Rockwool insulation in projects where fire resilience is highly needed.

Having said all these, it is important you, as the homeowner, rigorously prevent instances where your insulation is exposed to fire.

The commonest cause of insulation burning is an electrical malfunction. Notorious home accidents like overloaded circuits, pest-inflicted wire breaches, and lighting are known for triggering insulation fires.

Always ensure that you inspect your insulation regularly. Particularly, if your insulation is deployed in the attic, spare some time to check it at least once a year.

This goes a long way in preventing fire hazards.

Lastly, when installing your home insulation, spare the effort and dollars to install a fire barrier alongside. Such barriers in your home suppress the internal dispersal of fire.