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Attic Insulation
Key Takeaways
- 1Up to 25% of a home’s heat is lost through its roof.
- 2Attic insulation can be done at the loft or rafter level.
- 3Attic Insulation costs between €2,500 and €6,500 without a grant
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A grant of up to €2,000 is available for most homeowners to get attic insulation.
Adding more attic insulation to your home can save you hundreds of euro each year on your heating bills, as well as making it more environmentally friendly and valuable. This should be the first port of call for anyone seeking to make home energy improvements. In this guide, we explain the methods and materials used in attic insulation, and how they will affect your home.
What is Attic Insulation?
Attic Insulation is one of the simplest and most affordable ways to dramatically reduce the amount of heat loss in your home.
There are two different ways to insulate the attic: between the joists at the loft level or between the rafters at the roof level. In both cases, insulation is applied between the timbers to help keep heat in. This reduces the amount escaping into the attic or through the roof.
How much does Attic Insulation cost?
Attic insulation will typically cost between €2,000 and €2,500 for an Irish home. The median cost of getting attic insulation in a semi-detached house in 2025 was €1,983. This cost can be further reduced by getting an SEAI grant, which can cover more than half of the price.
The cost of attic insulation for your home depends on these factors:
Attic Size: The larger your attic is and the greater the area that needs insulating, the higher the cost will be.
Area to be Insulated: Insulating a home’s rafters is typically more expensive than insulating the loft due to the larger surface area and extra work required.
Insulation Type: Some insulations are more expensive than others. Mineral wool costs more than fibreglass, and spray foam is more expensive than blown fibres.
Extra Work Needed: If your attic needs additional work, such as installing ventilation, laying down loft flooring, or insulating pipes, this will raise the price.
Source: SEAI data on costs submitted for Better Energy Homes scheme from Jan – June 2025
Extra elements that many homeowners may choose to install at the same time as attic insulation include:
Pipe Lagging: If you have exposed pipes in your attic, it would be advisable to insulate them to prevent them from freezing and reduce your energy bills for hot water.
Insulated Flooring: Adding insulated flooring with loft insulation can make the storage space more accessible while also ensuring there is no gap in protection.
Attic Stairs: An insulated staircase and hatch will ensure that there is no major gap in insulation at the entrance to your attic.
Water Tank Replacement: If you have a galvanised cold water tank, then you will need to replace it with a plastic tank to receive the attic insulation grant.
Ventilation: Some homes may need to install additional ventilation if adding insulation at the rafter level.
Attic Insulation Grants Ireland 2026
The SEAI provides grant funding to help homeowners with the cost of installing attic insulation. The value of this grant depends on the type of home that you have.
Note: Rafter insulation grants are only available if applying through the SEAI’s One Stop Shop Scheme. Attic/Loft insulation grants are available both for individual upgrades and through the one stop shop.
Read more about SEAI Home Insulation Grants.
Best Types of Attic Insulation
There are multiple types of attic insulation materials with different strengths and weaknesses. Which is best for your home will depend on where you are getting insulation installed, your budget, and ease of access.
Mineral Wool and fibreglass insulation are made from rock or glass melted down and spun into fibres. This is then spun into mats before being given its final shape. These days, mineral wool has largely replaced fibreglass as the insulation of choice.
Insulation Shapes: These primarily come in long rolls or thicker, denser batts. Some fibreglass insulation may also be found as loose fill material in older homes.
Best Use: This is most commonly used for loft joists. Attic roll insulation can be applied easily and quickly for excellent results.
Spray foam insulation consists of a liquid polyurethane foam that is applied with a spray gun to the surface you want to insulate. It then expands massively and hardens after being applied, creating a layer of insulation. Open cell spray foam insulation is used in attics since it is more moisture permeable than closed cell foam insulation.
Insulation Shape: Spray Foam is applied as a liquid before expanding. This means that it can be used in areas of all different shapes and sizes, including areas that might be trickier to get to with solid insulation.
Best Use: In attic insulation, open cell spray foam insulation is often used at the rafter, applied below the roof. This requires less work to secure it than solid insulation.
Loose fill insulation consists of material that is either poured or sprayed into an area that needs to be insulated. In modern usage, it is either loose fibreglass, rather than compacted rolls, or blown cellulose insulation.
Blown cellulose insulation is made from wood or paper fibres that are blown into empty spaces that need to be insulated.
Insulation Shape: Blown Cellulose and loose fibreglass can fit into any area and don’t come with a predetermined shape.
Best Use: Loose fill insulation is best used between loft joists where gravity can keep it down. It would be impractical to try to secure it in place at the roof level.
Solid boards of insulation made from foamed polystyrene, polyiso, or polyurethane are commonly used in many types of insulation projects.
Sometimes referred to as PIR board insulation, they have a strong thermal performance and can be easily cut to fit different shapes and sizes. Kingspan, IKO, Ecotherm, and Recticell are some of the larger manufacturers of solid insulation in Ireland.
Insulation Shape: These come as rectangular boards of insulation approximately 2.4m x 1.2m in size, and between 40mm and 120mm thick. However, the boards can be easily cut into different shapes.
Best Use: Rigid Boards are more commonly used for rafter insulation because they are easier to place between rafters on a pitched roof than wool products.
Loft Roll Insulation
Loft Roll insulation refers to placing insulation between the loft joists in your attic. This is usually done with rolls of batts of mineral wool, sheep’s wool, or fibreglass.
When insulating between loft joists, you should aim to install a total of 300mm of insulation to get the best performance. This could be 200mm on top of what is already present, or 300mm of mineral wool.
Why get loft insulation?
Insulating between the loft joists is the best option if you plan to leave the attic as a storage space rather than converting it into a living space.
Heat Envelope: Insulating the loft joists will leave a smaller area of your home to be heated. This means even lower heating bills. The attic will remain a cold space however.
Storage Space: It is simple to put down boards on top of mineral wool insulation to more easily move around the attic afterwards.
Future Conversion: Putting insulation in the loft is not the best choice if you plan to convert the attic. This is because more rafter insulation will be required to make the space comfortable for living in.
Rafter Insulation
Rafter insulation is another way of insulating your attic that involves applying insulation to the underside of the roof. Either rigid boards of insulation are fixed between the rafters, or spray foam insulation is applied to the same space.
Why get rafter insulation?
Having the rafters of your attic insulated, rather than doing it at the loft level, is a good choice if you plan to convert the attic to another use later.
Heat Envelope: If you put insulation at the rafters then the heat envelope goes as far as the roof. This makes the attic a warm rather than cold space.
Time to Install Insulation: If you plan on converting your attic, you should install rafter insulation first. It will be much harder to try and do afterwards, if its even possible.
Comfortable Temperature: Without rafter insulation, any living space at the attic level will get very cold in winter, and extremely hot in summer. This is because it cannot regulate the transfer of heat.
Warm Roof vs Cold Roof
There are two ways to apply rafter insulation that will result in either a warm roof or a cold roof. This depends on whether the insulation is placed either between the rafter joists or above them.
Warm Roof
Insulation Location: The insulation is placed above and on top of the rafters.
Thermal Performance: This typically has a better thermal performance and energy efficiency than a cold roof due to the continuous layer of insulation.
More Expensive: This is the more expensive method for installing rafter insulation.
Higher Roof Profile: Installing insulation above the rafters can raise the profile of your roof.
Lower Condensation Risk: With a vapour barrier between the insulation and the rafters there is a lower risk of condensation and damp developing.
Cold Roof
Insulation Location: The insulation is placed between or directly below the rafter joists.
Ventilation Required: With a cold roof, you need to leave an air gap between the insulation and the roof to prevent damp.
Less Expensive: Getting a cold roof installed is less expensive when considering attic insulation.
Lower Roof Profile: A cold roof setup will not affect the profile or appearance of your roof in any way.
Benefits of Attic Insulation
There are many benefits to having better attic insulation. Primarily, it will save you money while also making your home more comfortable and environmentally friendly.
Enjoy a Warmer Home
Prevent Heat Loss: You can reduce the amount of heat escaping your home by up to 25% with a properly insulated attic.
Easier to Warm: With a good insulation seal around a smaller area of your home, your heating system won’t struggle as much to heat the place up. It will also stay warm for far longer.
Save on Energy Usage: With attic insulation installed it takes far less fuel to get your home warm, and keep it warm during winter.
Reduce Your Energy Bills
Slashing your heating bills by 25% could save Irish households €300 a year or more on their heating bills by reducing gas, oil, or electricity consumption.
Increase Property Value
Improved BER: Adding insulation is one of the easiest ways to improve the BER of your home. This is becoming an increasingly important factor in property prices.
Lower Bills: Advertising lower energy bills is a key selling point for property owners.
Installation Process
The process for installing attic insulation varies depending on where the work is being done and the type of insulation that you’re getting.
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Prepare Tanks & Pipes: if you have a water tank or pipes in the attic, then they should be insulated first, before laying down loft insulation.
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Remove Obstacles: Make sure that any high load electrical cables are lifted out of the way so that they can be laid on top of the insulation, not beneath it.
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Check Existing Insulation: If there is any existing insulation in place, such as fibreglass rolls or loose fill, check it for any damage from damp or mould. If the insulation is undamaged, leave it in place.
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Ensure Ventilation Gaps: Check to make sure the attic has ventilation at the eaves or elsewhere to prevent damp issues.
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Lay Down Mineral Wool: Rolls or batts of mineral wool insulation should be placed between the joists of the attic loft, reaching to the top of the joists.
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Add Second Layer: Add another layer of mineral wool on top of the first at right angles to it. This should bring you to the total desired depth of 300mm of insulation.
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Insulate Hatch: If you have an attic hatch, insulation should be added to it once the rest of the loft is complete.
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Clear the Space: Ensure that the space in your attic and around the rafter is completely clear of obstacles.
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Applying Solid Insulation: With mineral wool or rigid board insulation, these sections are cut to measure and fitted between or below the rafter joists. Depending on the circumstances, battens or netting may be needed to hold them in place.
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Leave Ventilation Gap: With solid insulation, a gap of 50mm needs to be left between the insulation and the roof to provide ventilation.
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Applying Spray Foam Insulation: Spray Foam Insulation is applied directly to the underside of the roof membrane.
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Leave Rafters Exposed: If applying spray foam insulation, the underside of the rafters must be left exposed in order to prevent excessive condensation.
Attic Insulation FAQs
Attic insulation should last for at least 40 years. But can be fine for far longer, or degrade quicker, depending on the materials used and the condition that it is in. Fibreglass and blown cellulose insulation have shorter lifespans, while mineral wool insulation can last for up to 100 years.
It depends. If any existing loft roll insulation has been damaged by damp or mould, then it should be removed to stop it from spreading. If the old insulation is still in good condition, then you should leave it in place.
Yes, if spray foam insulation is not properly applied, it can damage your roof. The most common problem with spray foam is that someone covers up the rafters entirely. The foam should be applied between the rafters, but they must be left exposed to prevent damp.
If adding attic insulation to a protected home, you must choose the material carefully. Older buildings have different materials and construction methods. The best bet is to use non-invasive methods and materials such as Sheep’s Wool, which is also very breathable.
