How safe is your attic insulation?

Okay, so. Let’s talk about your attic.

I want you to picture it. It’s probably full of half-empty paint tins, a suitcase with a broken wheel, and the box for every expensive electronic device you’ve bought since 2011. It’s the “Room of Requirement” for domestic junk. It’s the place you put things you don’t want to deal with.

But it’s also the Most Important Room in Your House for one specific, depressing reason: it’s the giant, leaky sieve through which all the expensive, precious heat you pay for is escaping into the cold, indifferent universe.

You know this. You’re smart. You’ve seen the SEAI grants advertised. You’ve heard your neighbour brag about their BER rating. You’re on a quest to make your home a cozy, energy-efficient fortress, not a glorified wind tunnel that’s haemorrhaging euros.

So you decide to join the great national crusade of home energy upgrades and finally do something about that sieve. Your first, most logical thought is attic insulation.

This is the correct thought. Of all the things you can do, sorting out your insulation is almost always the best bang for your buck. It’s the “put on a jumper before you turn up the thermostat” of home ownership. Think about it: you can install the world’s fanciest heat pump, you can get the slickest solar panels, but if your attic is a leaky sieve, you’re just heating the sky more efficiently. This logic is why everyone is rightly obsessed with their home’s thermal performance, a mission that has been made even more urgent by Ireland’s ambitious retrofitting targets.

So you start looking. And you immediately fall down a rabbit hole of U-values, thermal conductivity, and competing claims. You see big, shiny, rigid boards. You see fluffy, woolly rolls. You see people in space suits spraying foam.

And you’ll pick one. The installer will come, they’ll roll it out or spray it on, and you’ll high-five yourself. Your BER rating will go up. Your heating bills will go down. You will be a Hero of Domestic Efficiency.

But there’s a question you didn’t ask. A number you didn’t check. A secret, printed in tiny letters on a technical document you’ve never heard of, that reveals something deeply, deeply unsettling.

What happens if that stuff catches on fire?

You probably assume, “It’s insulation. It’s a building material. It’s probably… fine? Right? They wouldn’t be allowed to sell it if it was dangerous?”

Oh, my sweet summer child.

Welcome to the most important, least-discussed topic in home insulation: Fire Safety Ratings. It turns out that not all insulation is created equal. Some of it is virtually fireproof. And some of it… well, some of it is closer to solid-state gasoline.

And the scariest part? Some of the most popular, most common, best-insulating materials on the market are in the second category.

This is the Unseen Danger. And today, we’re going to drag it into the light.

First, A Quick Trip to Bureaucracy Land (It’s Important, I Swear)

I know, I know. Standards. Classifications. European-level bureaucracy. You can feel your soul leaving your body. But stay with me, because this is the secret decoder ring for everything.

Every construction product sold in the EU has to be tested for how it reacts to fire. The standard they use is called EN 13501-1. This is the definitive, harmonised European standard. You can even go read the official EU documentation on it if you are a specific kind of fun at parties.

This standard is basically a report card that tells you, “If a fire starts, is this material going to help, hurt, or just sit there judgmentally?”

It’s crucial to know this isn’t “Fire Resistance.” “Fire Resistance” is a system property—it measures how long a whole wall (plasterboard + studs + insulation) can stop a fire from getting from one room to another. “Reaction to Fire” (our standard) is a material property. It answers the simple, brutal question: “If you put a flame to this material, what does it do? Does it fuel the fire?”

This report card has three parts:

1. The Main Grade (A1 to F): How much does this material contribute to the fire?
2. The Smoke Grade (s1 to s3): How much smoke does it pump out when it burns?
3. The Droplet Grade (d0 to d2): Does it drip flaming bits of itself everywhere?

So, a product’s final grade looks something like B-s1, d0.

This code is the only thing you should trust. Ignore vague marketing terms. This Euroclass rating is the legally-binding, scientifically-tested truth.

Let’s pretend these grades are people at a party that suddenly catches on fire.

The Main Event: The “Contribution to Fire” Grade (A1 to F)

This is the big letter. It tells you how much “fuel” the material adds to the fire.

Class A1: The Zen Master.
This is a rock. Or glass. Or ceramic. You can hold a blowtorch to it, and it will just sit there, bored. It is non-combustible. It cannot and will not burn. It adds zero fuel to the fire. To get this grade, a product has to pass two brutal tests: the EN ISO 1182 (Non-combustibility test), where it’s roasted in a $750^circtext{C}$ furnace for 30 minutes, and the EN ISO 1716 (Heat of Combustion test). It must show almost no reaction. Because it’s non-combustible, it doesn’t even get a smoke or droplet rating. It’s the undisputed champion of fire safety.

Class A2: The Zen Master’s Cousin.
This is 99% rock, but maybe it’s got a tiny bit of paint on it, or a thin paper facing. It’s almost completely non-combustible, with “very limited” contribution to fire. It’s so safe, in fact, that it’s approved for use on high-rise buildings. Unlike A1, it does get tested for smoke and droplets.

Class B: The Ninja.
This is the first “combustible” class. This material can burn, but it’s had a lot of training. It has “very limited contribution” to fire. It resists ignition, and even when it does burn, it releases heat very slowly. It will not cause a flashover. A flashover is the terrifying phenomenon you see in movies where the whole room just erupts in fire at once, which you can see in these fire behavior videos.

Class C: The “Meh” Guy.
This guy is also combustible, but has a “limited contribution” to fire. He’ll resist for a bit, but once he gets going, he’s definitely part of the problem. He will contribute to a flashover, but it takes him longer than the guys below.

Class D: The “Acceptable” Problem.
This guy has a “medium contribution” to fire. This is what most people would call “flammable.” He’ll catch fire, he’ll spread it, and he’ll happily contribute to a flashover. This is considered an “acceptable” contribution for many standard products.

Class E: The Liability.
This guy has a “high contribution to fire”. He will resist only a small flame attack for a very short period. He is basically just fuel waiting for a spark.

Class F: The Arsonist.
This is the worst grade. This is the guy who showed up to the party soaked in gasoline. Class F means the product is “easily flammable” or, even worse, the manufacturer didn’t even bother to test it, so “No Performance Determined”. It fails to even meet the bare minimum requirements for Class E.

All these combustible grades (B-E) are decided by the Single Burning Item (SBI) test. This is literally a test that simulates a wastepaper basket on fire in the corner of a room, and scientists measure how badly the material freaks out.

The Fire Party Grades.

The Two “Unseen Killers”: Smoke (s) and Droplets (d)

In many ways, these little letters are even more important than the big letter. In a real fire, it’s not the flame that gets you. It’s the smoke. And in an attic, the last thing you want is fire raining down on your head.

The ‘s’ Rating (Smoke): How Fast Does It Blind You?

This measures the rate and total amount of smoke produced.

• s1: Low Smoke. This is the best. Minimal smoke. You can still see the exit. (Technically, a Smoke Growth Rate (SMOGRA) of $le 30 text{ m}^2text{s}^{-2}$).
• s2: Medium Smoke. “Quite a lot of smoke”. Visibility is getting bad, fast. (SMOGRA $le 180 text{ m}^2text{s}^{-2}$).
• s3: High Smoke. “Substantial smoke”. The room is black. You are choking. This is a life-or-death situation.

The ‘d’ Rating (Droplets): Is It Raining Fire?

This one is critical for attics. If your insulation melts, does it drip?

• d0: No Droplets. The material never produces a single flaming droplet during the 10-minute test. It will not spread the fire to the floor below. This is the hero.
• d1: Limited Droplets. Some drips, but they burn out in less than 10 seconds. Not great, but manageable.
• d2: High Droplets. “Intense dripping”. It’s raining molten lava. The insulation is on fire, and it is now efficiently spreading that fire to your carpets, your sofa, your bed. This is a catastrophe.

The ‘Unseen Killers’.

So, your ideal product is A1 (the Zen Master).

Your next best product is A2-s1,d0 or B-s1,d0 (the Ninja who doesn’t smoke and doesn’t drip fire).

Your absolute nightmare scenario is something like F-s3,d2. (The Arsonist who creates blinding smoke and rains fire). But surely, nobody sells that?

…Right?

The Big Reveal: What’s Actually In Your Attic?

I went and dug up the official, legally-binding “Declaration of Performance” (DoP) documents for the most common insulation materials sold in Ireland. These are the documents manufacturers must publish, and they cannot lie.

The results are… well, let’s go through them.

Tier 1: The Zen Masters (Euroclass A1)

These are the safest materials, full stop. They are non-combustible. They cannot burn.

Winner: Mineral Wool (Glass & Stone)
This is the fluffy stuff you see in rolls, like a big yellow or brown blanket. It’s what most people picture when they think of insulation.

• Products: ROCKWOOL (like Rollbatt, Thermal Insulation Roll, and Flexi), ISOVER (like Spacesaver and Metac), and Unilin Stonewool.
• Official Rating: EUROCLASS A1
• Analysis: This is it. This is the gold standard. It’s made from molten rock (basalt) or sand, spun into fibres. It just… doesn’t… burn. Manufacturer data sheets repeatedly call it “non-combustible” and the “highest possible rating”. You can see it right on their data sheets, like this one for Rockwool Rollbatt. It’s A1. It’s fire-safe. Full stop.

Surprise Winner: Specialist Multifoil
Multifoil is that thin, shiny, space-blanket-looking stuff. Most of it is… not A1. But one company (Superfoil) makes a specific version called SFNC+ (Non-Combustible).

• Product: Superfoil SFNC+
• Official Rating: EUROCLASS A1
• Analysis: This is a great example of why you have to check the exact product. The “normal” multifoil isn’t A1, but this specialist one is. It’s designed to be non-combustible and a thermal barrier.

A happy, smiling stick figure tucking a fluffy blanket (labeled “A1 Mineral Wool”) into an attic.

Tier 2: The Fire Ninjas (Euroclass B-s1,d0)

These materials are combustible, but they are highly engineered to be incredibly safe. They have very limited fire contribution, produce almost no smoke, and do not drip.

• Products: Xtratherm Thin-R Thermal Liner (XT/TL), Unilin Safe-R Fireline Laminate, Partel FOAMSEAL Liquid B1, Isolena Sheep’s Wool.
• Official Rating: EUROCLASS B-s1,d0
• Analysis: This is a fantastic rating. It’s the “gold standard” for any combustible product. The key here is that these are often composite boards. They’ve taken a foam core and bonded it to a fire-resisting layer (like plasterboard) in the factory. This “system” is engineered to be safe. Even high-end natural products like specially-treated sheep’s wool can achieve this, and specialist spray foams used for sealing gaps. This is a product that has been designed with fire in mind.

A cool, competent-looking stick figure in sunglasses.

Tier 3: The “Tigers in Cages” (Euroclass E & F)

And now, we arrive at the heart of the problem.

This category contains some of the most popular, well-known, and thermally-efficient insulation products on the entire Irish market. These are the rigid foam boards, often called PIR, PUR, or EPS. They are amazing at insulating. They have fantastic U-values.

And when they are “naked” — just the board itself, as it exists during construction or before it’s covered up — they have the worst fire ratings allowed by law.

Product 1: Rigid Polystyrene (EPS)
This is the white, “bubbly” foam. You’ve seen it as packaging. It’s also widely used in construction by companies like KORE and Jablite.

• Products: KORE EPS, Jablite EPS, and generic EPS.
• Official Rating: EUROCLASS E
• Analysis: Most EPS sold for building is “FR” (Fire Retarded) grade. This is what gets it a Class E. This means it has a “high contribution to fire”. Without the fire retardant, it’s Class F.

Product 2: Standard Spray Foam (PU)
The stuff that gets sprayed in, expands, and hardens.

• Products: Generic Polyurethane (PU) spray foams.
• Official Rating: EUROCLASS E
• Analysis: As noted by the Royal Institution of Chartered Surveyors, a typical rating for these foams is Class E, which “will only resist a small flame for a few seconds”. Again, this isn’t the specialist Class B foam. This is the standard stuff.

Product 3: Natural Fibres (Variable)
What about “eco-friendly” options like cellulose or sheep’s wool?

• Cellulose: This is literally recycled newspaper. It’s heavily treated with borate salts to make it fire-retardant. It’s designed to char instead of melt. But its performance is variable. The product standard minimum is Euroclass E, but some can be engineered to hit Class B.
• Sheep’s Wool: This also varies. While some basic products are Class C or D (or cited with old, non-Euroclass standards), specialist, treated versions can achieve the excellent B-s1,d0.
• Analysis: This proves, yet again, you must check the specific DoP. “Cellulose” or “Sheep’s Wool” tells you nothing. You could be getting a Class B Ninja or a Class E Liability.

Product 4: “Naked” Rigid PIR Boards
This is the big one. These are the foil-backed, high-performance, yellow/purple boards you see on every building site. They are made from Polyisocyanurate (PIR) foam. They are famous for being the best insulators.

• Products: Xtratherm Thin-R (naked board), Kingspan Thermapitch TP10.
• Official Rating: EUROCLASS E / F

I am not joking.

The Declaration of Performance for Xtratherm Thin-R gives it a Euroclass E.

The Declaration of Performance for Kingspan Thermapitch TP10—a market-leading product—states, clear as day, Reaction to Fire: F —a fact you can verify on their own official Declaration of Performance.

A “Class F” rating. The Arsonist. “Easily flammable”. The worst possible grade.

A terrified stick figure looking at a wall of angry-looking, foil-wrapped boards.

Okay, I’m Panicking. Should I Be Panicking?

Yes and no. Let’s take a breath. This is the “Wait But Why” part, where we figure out what this actually means.

How can the safest-sounding product (from the King of insulation, no less) have the worst possible fire rating?

This is the “Tiger in the Cage” analogy.

The manufacturers of these boards will correctly argue that the “naked” board rating (E or F) is not the final “as-installed” rating. These products are never intended to be left exposed. They are designed to be fully encapsulated—trapped—behind a “cage” of fire-resisting materials.

In your attic, this means the Class F board is installed between your rafters, and then it is completely covered by a layer of fire-rated plasterboard (the cage).

When you test that entire assembly—the plasterboard, the foam, the roof tiles—the system gets a great fire rating (e.g., it can hold back a fire for 30 or 60 minutes).

This is called Fire Resistance. The Euroclass (A1-F) system is called Reaction to Fire. They are two different things, and “Reaction to Fire” describes the material’s “raw flammability”.

So, as long as the cage is perfectly sealed, the tiger can’t get out. You are safe.

This Is Where The “Unseen Danger” Comes In

The “Tiger in the Cage” system relies on one, simple, terrifying assumption: That the cage is perfect.

What if it’s not?

Danger 1: The Construction Phase
For days, weeks, or months, that Class F “solid gasoline” is sitting exposed all over your attic. All it takes is one spark from a builder’s angle grinder, one electrical fault from a temporary light, or one dropped cigarette, and you don’t have a small fire. You have an inferno.

Danger 2: The “Gaps” (i.e., Real Life)
The cage is only as strong as its weakest point.

• What about the attic hatch? Is it perfectly sealed with fire-rated plasterboard? Or is it a flimsy bit of wood, with the exposed edge of the Class E/F foam right there?
• What about the recessed downlights you installed? Did the electrician just cut a hole in the plasterboard, leaving the light fitting (which gets hot) nestled right up against the Class E foam?
• What about the plumber who had to run a new pipe? Or the electrician who pulled a new wire? Did they just punch a hole through the “cage” and not seal it with a specialist, fire-rated sealant? (Which, by the way, should be a B-s1,d0-rated one like Partel’s).

Any breach in the plasterboard cage puts a heat source right next to the tiger.

This is the risk. You are trading peak thermal performance for peak fire risk, and you are betting your safety on the 100% perfect, life-long integrity of that plasterboard cage.

By contrast, when you use Euroclass A1 Mineral Wool, there is no tiger. You don’t need a cage. You can leave the insulation completely exposed. You can cut holes in your ceiling. You can have a spark. It. Does. Not. Burn. You have removed the “fuel” component from the equation entirely.

A simple two-panel comic.

So, What Should I Do? (The Conclusion)

You’re not a fire safety engineer. You’re just a person who wants a warm house that doesn’t cost a fortune to heat. So here is the simple, non-panicky takeaway.

When you’re looking at insulation, you now have two “main stats” to check, not one.

1. The U-Value (Thermal Performance): This is what everyone already checks. Lower is better.
2. The Euroclass (Fire Safety): This is the one you will now ask for.

You are now empowered. When an installer gives you a quote, you’re going to ask one simple question:

“What is the exact Euroclass EN 13501-1 rating for that product?”

If they fudge, or say “it’s fire-rated,” or “it meets regulations,” push them. Ask to see the Declaration of Performance (DoP). This is the legal document. They must have it.

When you look at it, you will know exactly what you’re dealing with:

• If the rating is A1, you are getting the safest product on the market. You can sleep soundly. This is the Zen Master.
• If the rating is B-s1,d0, you are getting a high-performance, engineered product that is extremely safe. This is the Fire Ninja.
• If the rating is E or F, you are getting the Tiger in the Cage. This doesn’t mean you must say no, but it means you are 100% reliant on the perfection of the installation. You must ensure it is fully, completely, and permanently sealed behind fire-rated plasterboard, with no gaps, ever.

Knowledge isn’t about panicking. It’s about understanding the choices you’re making. You might be surprised how many people are unaware of the different types of insulation, but learning the basics is the first step.

You are putting a high-tech material in the roof directly over your family’s heads. You have a right to know if it’s a fire-proof blanket or a block of solid fuel. Now, you do.

If you’d like to talk to someone who geeks out on this stuff and will only use the safest, most appropriate materials, you should have a chat with experts about your attic insulation, today.