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Here in Ireland where temperatures are on the low side and warm homes are essential ‘only one in 20 houses has top energy rating’ according to the Irish Times. In the UK only 38.6% have 200mm or more insulation in their attic and in the US around 90% of US homes are under-insulated. If you are one of those people who don’t have their attic properly insulated, then you will be losing around 25% of heat through this part of your house during the autumn and winter months.

Getting insulation installed in the attic is definitely a great decision, but what material is the best fit for the job?

Both Earthwool and Rockwool are safe and more eco-friendly options that have excellent insulation capabilities but could cost you over €15 per square meter depending on the thickness. The good-old Fiberglass insulation is not so good after all as it is an environmental and health hazard. However, it is the cheapest option available on the market nowadays.

Below, you’ll find a detailed comparison of the materials that will hopefully help you decide.


Rockwool is a type of mineral wool and is made out of…rocks!

The natural material gets heated up to 3.000 degrees. At such temperatures, rock melts and turns into a liquid. Then the liquid rock gets mixed with long fiber strands.

After that, the material gets compressed and, finally, is cut into convenient-to-use batts.

Acoustic capabilities 

Rockwool has amazing sound-deadening properties. Because of that, you might want to consider adding Rockwool not only to your attic but also to other places in your house.

Safety / Eco-friendliness 

Just as you would expect, anything made out of rocks is considered to be eco-friendly and safe. This type of insulation is made out of natural material and usually contains up to 75% of recycled contents.

Insulation Quality

Rockwool has increased insulation capabilities and an R-value of 23 and a thermal conductivity of 0.035 W/mK.

The material is fire-resistant (up to 1.400 degrees) which comes as no surprise as the insulation was literally made at 3.000 degrees. So, a regular fire is definitely not a threat. In fact, it is often code-required for Rockwool to be used between floors as a fire stopper.

Another important advantage – Rockwool is highly water-repellent. The water will simply roll off the material without getting soaked in the insulation.

Finally, the material allows any moisture to freely escape which means no mold-related problems. 


Rockwool comes in dense batts that can be easily cut to the perfect size. Moreover, the material can be conveniently fit into place – no stapling or other annoying manipulations required.

You will be able to easily install the insulation nice and tight, which is going to help avoid any future shifting.

As we have already mentioned, Rockwool is especially well-suited for installation in spaces that need insulation to have sound-deadening properties. But it is also suitable for crawlspaces, floors, ceilings, walls, and, of course, attics.


The only ‘downside’ of Rockwool is the cost.

Depending on the thickness this material can cost roughly €15 per square meter which makes it a little less than two times more expensive than fibreglass.

However, the cost should not become a turn-off in this specific case.

Firstly, Rockwool is incredibly durable. Such insulation won’t degrade over time and will serve you for decades (without becoming less effective).

Secondly, Rockwool has an increased R-value. This will help you keep the house nice and toasty without changing the settings on your thermostat. As a result, you’ll be able to save a small fortune on heating bills throughout the insulation’s lifespan.


There is only one brand out there that makes Earthwool – Knauf Insulation.

Basically, this type is glasswool insulation, but with a twist. It is made out of recycled bottles with the use of the ECOSE technology.

During the process, a very strong binder that bonds the strands together is created, but without the addition of any chemicals or artificial colouring.

Acoustic capabilities 

Just like traditional glasswool, Earthwool has excellent sound absorption.

By the way, Knauf Insulation has launched a special product named the ‘Sound Shield’. These batts are designed specifically to reduce sound transmission. 

Safety / Eco-friendliness  

Eco-friendliness is, perhaps,Earthwool’s main feature.

Firstly, the insulation is made out of recycled glass bottles.

Secondly, the ‘glass’ part is bonded together with an eco-friendly binder that is based on rapidly renewable resources, has no chemicals or artificial dyes added, and has a lower embodied energy.

Finally, Earthwool was certified as an ‘outstanding material’ by Eurofins. 

Insulation Quality 

The Earthwool comes in a wide range of R-values which makes it easy for anyone to find the perfect option for their specific situation. The insulation capabilities vary from R-14 to up to an R-value higher than 30. It has a thermal conductivity of 0.044 W/mK.

The material also comes in multiple thicknesses and is fire resistant. It is non-combustible, does not absorb any moisture, and, consequently, does not encourage mold growth


Earthwool is an incredibly pleasant material to work with as it is much softer than other types of glasswool. Moreover, it is less dusty and won’t make you itch after the installation process is complete.

The insulation comes in convenient batts or rolls that are highly compressed. That basically means that the packages won’t take up too much space in your house and that you’re going to need to order fewer packages than in the case with traditional glasswool.

You can easily cut the material that has a lovely natural brown colour with a sharp knife. By the way, earthwool is practically odourless as there are no petrol-based chemicals used during the manufacturing process. 


The insulation comes with a 50-year warranty. Earthwool is highly durable and you wouldn’t have to worry about changing your insulation every decade (or even less).

The price would depend on the insulation’s R-value and the thickness you choose.

It can start from less than €5 per square metre which is a decent price for the benefits offered by this insulating material.


Perhaps, the most widespread insulation material that is usually used in batts, rolls, or loose-fill.

As the name suggests, this type of insulation is made out of fine fibers of glass.

Acoustic capabilities 

Fiberglass will not make a space completely soundproof but is a relatively good sound barrier. The effect would certainly depend on the thickness of the insulation. The thicker the material – the more noise it is going to absorb.

Fact: fiberglass is also great at reducing echoes inside a room.  

Safety / Eco-friendliness

Unfortunately, fiberglass will not decompose over the course of time. That means that once thrown away, this type of insulation will sit in a landfill.

The material is definitely an environmental hazard as it requires tons of energy during the production process (there is also a constant release of VOCs and other dangerous air pollutants).

The insulation material is, in most cases, treated with formaldehyde – a toxic chemical. Formaldehyde can not only affect our health, but it can also leak into the ground when the fiberglass is thrown away.

Furthermore, fiberglass can be dangerous for your health. First of all, people can inhale the material and, in such a case, tiny pieces of glass are going to settle in the lungs.

A more widespread health concern is irritation. When exposed to fiberglass, you might start to itch or cough and develop various skin problems.

Insulation Quality

Fiberglass can withstand temperatures close to 1000 degrees before beginning to melt. Moreover, the material is not flammable.

This insulation doesn’t hold or retain water, but it can get ruined if it ever gets damp or wet (which can totally happen, in case it has been used in the attic).

Fiberglass blankets have an R-value of around 3.2 (per every inch of thickness). So, a 6-inch batt will achieve an R-value of a little more than 19.

Fiberglass can have a thermal conductivity of up to 0.040 W/mK

You can also find some high-performance products on the market nowadays that have increased insulation capabilities.


It is relatively easy to install Fiberglass insulation as you are only going to need a few basic tools to make the thing work.

However, tight-fitting the batts might be a bit challenging. Do bear in mind that every gap is going to drastically decrease the effectiveness of the insulation.

The biggest problem with this material is that it can cause skin, eye, and lung irritations. So, when working with this type of insulation you have to be extremely careful and you have to be wearing a face mask, goggles, gloves, and appropriate clothing (like long trousers and a long-sleeved shirt). 


The best part about Fiberglass insulation is the price as it’s the cheapest option available on the market.

A square metre of this material will cost you anywhere between €0.30 and €1.50.

To Sum Up

Rockwool, Earthwool or fibreglass? Best attic insulation – which one should you go for?

If you can spend a little more on the installation of new insulation, go for Earthwool or Rockwool.

These materials are eco-friendly and safe for your health. Moreover, they are extremely durable and have amazing R-values – it’s definitely an investment that is going to pay off over time.

If you are looking for an environmentally friendly and safe alternative to all of the above insulations then perhaps Hemp or Sheeps Wool would be more suited to you.

Installing Hemp and Sheep Wool does not require goggles, masks or gloves to install.

You can read more about Sheep Wool insulation here and Hemp here.