Fiberglass itself is naturally non-combustible because it is made of glass, meaning it will not ignite and has a high melting point. However, standard insulation batts often include flammable resin binders and paper (kraft) or foil facings, which can easily catch fire or produce heavy smoke when exposed to an open flame.
Fiberglass is naturally non-combustible and does not require additional fire-retardant chemicals. It holds a Class A fire rating, meaning it resists flame spread and contributes very little smoke. This makes it a popular choice for homes and buildings where fire safety is a top concern.
Yes, it is safe to insulate over or around modern, insulated wiring like Romex/NM. In older homes DO NOT insulate over or around knob and tube wiring. This is some of the oldest types of wiring and can have exposed, uninsulated conductors. This type of wiring relies on open air space around the wires for cooling.
Fiberglass and mineral wool insulation
Materials are noncombustible, and remain so for the life of the product. They require no additional fire-retardant chemical treatments—in fact, unfaced fiberglass and mineral wool are accepted as a fire block in wood frames.
Pink fiberglass insulation is naturally non-combustible and fire-resistant, as it is made primarily of spun glass fibers. It will not easily ignite or spread fire. However, there are a few important caveats regarding its overall fire safety:
Fire-rated spray foam, primarily available as expanding fireblock or specialized firestop formulations, is designed to seal gaps around utility penetrations. It effectively impedes the spread of flames, smoke, and toxic hot gases between compartments while maintaining the structural integrity of a fire-rated wall or floor.
Because spray foam can trap moisture, hide the condition of the roof, make it difficult for surveyors to inspect, which means risks like timber decay, dry rot, and not forgetting increased fire risk. If you've got it or you're buying a property that does, this is something you need to know upfront.
ROCKWOOL insulation is made from non-combustible stone wool that can withstand temperatures in excess of 1,000°C1. This helps limit the spread of fire in a building.
There's no such thing as a “fireproof” safe as all containers will inevitably burn after some time. Currently, there isn't a standardized test that could fully back the “fireproof” claim that many brands out there label their safes with.
No material can completely fireproof a house. In the right conditions and temperatures, any material can burn or melt, including steel and concrete. The better approach is to build with fire-resistant materials and use fire-resilient design choices and building methods.
Romex can be installed above or under the insulation. It is OK to touch the outer jacket with your bare hands provided the insulation is not damaged. A good rule of thumb when working with electricity is to wear insulated (rubber sole) shoes and to always keep one hand in your pocket.
Fiberglass is an excellent electrical insulator, meaning it does not conduct electricity under normal conditions. This property makes it a safe, go-to material for electrical housings, ladders, and wiring insulation.
What time of year is Insulation cheapest?
Fiberglass itself will not burn or catch fire because it is made of glass fibers. However, the resin binders used to hold the fibers together will melt and degrade at high temperatures (400∘F400 raised to the composed with power F400∘F to 500∘F500 raised to the composed with power F500∘F). Furthermore, facing materials commonly attached to fiberglass, like kraft paper or foil, are highly combustible.
The healthiest, non-toxic insulation for your home is natural sheep's wool or hemp insulation. These materials contain no chemical binders or formaldehyde, actively regulate indoor humidity to prevent mold, and do not off-gas.
While the health risks of asbestos fibers are well-documented, fiberglass is less understood. Like asbestos, fiberglass poses some health risks, but these are less serious than those associated with asbestos. Asbestos is widely recognized as a carcinogen and a leading cause of mesothelioma.
6 of the Most Flammable Household Items
Yes, money can burn in a fireproof safe. While the safe's exterior protects against direct flames, the interior temperature can rise above $350∘F (the point where paper begins to scorch and char). Safes are rated by how long they can keep internal temperatures below this threshold.
In the UK, achieving a 60-minute fire resistance rating for ceilings typically requires installing two layers of 12.5 mm fire-resistant plasterboard. This approach is commonly recommended by manufacturers and aligns with British Standards for fire safety in residential buildings.
ROCKWOOL insulation is made from non-combustible fire-resistant stone wool that can withstand temperatures above 1,000°C1. This helps limit the spread of fire in a building. With minimal organic content, no significant toxic smoke is produced either.
Closed cell spray foam is rigid once set. It is a better thermal insulator and was previously sold to stabilise failing roofs. But if it has been used inappropriately or installed poorly, it might put stress on timbers, restrict air circulation and put them at risk of decaying.
Fiberglass particles typically stay in the lungs for a relatively short period, ranging from a few days to a few weeks. Unlike asbestos, modern fiberglass is engineered to dissolve or break down, allowing the body’s immune cells (macrophages) to digest and clear the fragments.
When balancing upfront cost and overall thermal efficiency, the cheapest and most effective standard insulation is fiberglass batt insulation. However, if you are looking for long-term savings through superior air sealing, dense-pack cellulose often provides the best overall value.
Foam insulation is a common target because it's easy for them to chew through. The material offers little resistance, allowing mice to create tunnels or nests within the insulation. But mice aren't just interested in chewing for the sake of it—they're also drawn to the warmth and shelter insulation provides.
WD-40 affects foam in different ways depending on the type of foam. It is highly useful for cleaning, holding, or dissolving, but can cause permanent damage to certain materials.