Heat rises is a simple axiom, and this means that your attic is one of the easiest ways for heat to escape from your home. In the same vein, insulating your attic is also one of the simplest things which can be done to help

Attic Insulation

What is Attic Insulation

Attic Insulation consists of adding layers of insulation to the internal surface of your attic and roof to prevent heat from escaping. 

Up to 30% of your home’s heat can be lost through the roof, so this should be one of the first steps taken for anyone looking to make their home more energy efficient and environmentally friendly.

There are two main areas where you can add insulation to your attic:

  • Between the joists of the ceiling
  • Between the rafters of the pitched roof of the building

The effectiveness of insulation used in your attic is typically measured through either its R-value or its U-value. A higher R-value is good, whereas the lower the U-value the better the result.

An R-value, expressed as Km²/W measures the thermal resistance of an insulation material, how good it is at blocking heat from passing through,

The U-value, expressed as W/m²K, measures how much heat passes through an area. This takes into account more values in the complete project such as the thickness of the insulation layer, and other factors.

Do I Need Attic Insulation

If you have an attic in your home there’s a good chance that there will already be some insulation present. Rolls of wool insulation are probably the most common older type of insulation, and can typically be found laid between ceiling joists in the attic.

But even if you already have insulation, that doesn’t mean you should disregard improvements in that area. Having a thicker layer of insulation, or adding more modern insulation can drastically improve how much heat can be kept in your home.

If your home doesn’t have any insulation in the attic, more likely with older buildings, then it’s an even easier choice to make.

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How Much Can You Save With Attic Insulation

Having proper attic insulation installed can save the average homeowner as much as 15% on their heating bills. 

With an average annual gas bill of €1,474.27 in Ireland, homeowners using gas for heating can easily expect to save roughly €200 – €250 each year. Savings are likely to be even higher for people currently relying on oil heating.

Benefits of Attic Insulation

When considering home insulation, the following factors should be considered.

Having good insulation in your attic will cut down the heat escaping your home, and save money on your heating bills in winter.

Insulation in your attic can help reduce or prevent altogether a lot of problems which come from damp and water vapour. Insulation can act as a barrier against water vapour seeping into your property and damaging the walls and roof, along with preventing mould and rot.

Attic Insulation is probably the simplest type of insulation to have installed on an existing home, as it requires no other material alterations to the existing property.

Where a hot water cylinder is present in the attic, adding insulation to the tank is a common part of any project. This means that your hot water cylinder will lose heat more slowly, reducing hot water costs. This is of particular benefit for homes with fewer occupants, and low hot water needs.

Insulating your attic will help to make your home a more comfortable place by making it easier to keep it warm and cosy.

Anything that cuts down on the amount of heating required in your home, whether through oil, gas, or electricity, will cut emissions from your home and give you a reduced carbon footprint.

Any time of energy efficiency improvements to your home will help increase its BER and raise the value of the property. This helps to make your home into a better long term investment and asset.

Types of Attic Insulation

The best materials to use for insulating your attic will vary based on where you are having them installed. Solid boards or rolled wool insulation is simple to install between the joists, whereas sprayed on cellulose or polyurethane foam is a popular choice for applying to rafters.

The most common and easiest to apply type of attic insulation. Rolled Wool insulation consists of layers of glass wool (fibreglass), wood wool, rock wool, or sheep’s wool which is rolled out, as the name suggests. Different materials will have different levels of thermal conductivity. 

Fibreglass and Rock wool also have the advantage of being very fire-resistant.

The most important factors to take into consideration are the density of the material being used and the thickness of the layers being set down. Both of which will affect how much insulation is provided.

An environmentally friendly, efficient and cost-effective method of insulation, Cellulose is made of recycled paper products which are cut down into tiny fragments and then made into a fibrous material which can be blown into small spaces.

The advantages of cellulose insulation include that it can be used over flat surfaces, but also in small spaces and niches to ensure complete protection with no gaps or air pockets.

Polyurethane is a sprayable foam that is excellent for insulating areas with lots of small spaces or otherwise in hard-to-reach areas such as attics or cavity walls.

Easily usable in new or old buildings, polyurethane is also completely airtight and has excellent thermal performance minimising heat loss.

 The water-resistant seal provided by the spray foam insulation also protects from rain and dampness. Spray Foam insulation will also expand as it dries and hardens, filling every crevice.

Polystyrene Insulation is a type of thermoplastic foam which comes in the shape of rigid boards. This is popular as a form of insulation due to its adaptability, ease of application, and excellent protection against heat loss and noise.

Types of Attic Insulation

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How Much Does Attic Insulation Cost

The cost of having your attic insulated will depend on numerous factors related to the size of the area and the insulation being used. The final price of the project can be determined by:

  • The size of the attic
  • Is Insulation being placed in the ceiling and/or rafters?
  • If any insulation is already present
  • What type of insulation is being used
  • What thickness of insulation is being installed
How Much Does Attic Insulation Cost

The insulation material you choose will have the most impact on the final price. While selecting a cheaper option might give some savings up front, you must also consider their thermal performance.

Selecting a cheaper insulation option might seem like a good decision up front, but it will reduce the amount you can save on your heating bills. Some materials might also have shorter lifespans than their more expensive counterparts. 

The cost of insulation materials for your attic per m² will fit in the average range of:

  • Sheep’s Wool/Mineral Wool/Fibreglass: €10 – €30
  • Polyurethane Foam: €25 – €60
  • Polystyrene Board: €10 – €20
  • Blown Cellulose: €2.50 – €5

The exact cost of the materials will depend on the thickness of the layer of insulation being put down. This is only the cost of the materials, the full cost per m² will also include labour, which will add significant expenditure.

The cost of attic insulation can vary anywhere from €600 – €4,000 depending on the size of your attic and the material used.

Rafter insulation for a pitched roof will typically cost more, with a larger surface than the base of the attic, and with more expensive polystyrene and spray foam insulation as more popular materials.

These are only rough estimates and are subject to change based on the cost of materials and each individual property.

Attic Insulation Grants

The SEAI provides grant funding for homeowners to help homeowners with the cost of having insulation installed in their attic and rafters.

These grants are available for all homeowners, including private landlords, so long as the home was built and occupied prior to 2011.

Insulation Type Grant Value
Attic Insulation Apartment (Any) – €800
Mid-Terrace House – €1,200
Semi-Detached/End-Terrace – €1,300
Detached House – €1,500 
Rafter Insulation Apartment (Any) – €1,500
Mid-Terrace House – €2,000
Semi-Detached/End-Terrace – €3,000
Detached House – €3,000

Note: Not all grants are available under the same streams of SEAI funding. Attic Insulation is available individually or as part of a larger project. Rafter Insulation grants, however, are only available through the One Stop Shop or Fully Funded Energy Upgrades schemes.

Homeowners who make use of grants for attic or rafter insulation through the Better Energy Homes scheme are required to achieve a final U-value of 0.16 W/m²K for ceiling insulation or 0.20 W/m²K  for rafter insulation.


The thickness of the attic insulation you have installed should be determined by what kind of performance you are looking for in concert with what your budget for the project is. Thicker layers of insulation will provide a better thermal performance, but will also cost more.

Fibreglass or cellulose insulation should probably be inspected after 15 years or so, at which point it may be replaced. However other materials such as mineral wool, polystyrene boards, or spray foam can be good for up to 100 years if installed correctly.

While it is of course possible to buy all the materials and equipment required for a DIY job, installing insulation yourself can have severe consequences if done incorrectly. Not only may you not get the desired benefits, but you could also end up damaging your home.

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