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External Wall Insulation Ireland (2026 Guide)
External Wall Insulation is one of the most comprehensive ways to improve the performance of your home in terms of heat loss and energy efficiency. External Insulation can be the most expensive way to insulate your home in Ireland, but the potential benefits are huge.
Key Takeaways
- 1External Insulation costs and average of €10,000 – €35,000
- 2A maximum SEAI grant of €8,000 is available for EWI
- 3External Insulation may require planning permission depending on your home and locality.
- 4Up to 30% of a home’s heat is lost through its exterior walls.
What is External Wall Insulation (EWI)?
External Wall Insulation is a layer of solid insulation applied to the outside of your home’s external walls. A complete EWI system consists of multiple layers that are meant to combine to form an airtight seal, reduce heat loss through the walls, and also provide additional structural support and weather protection.
This is typically done as a complete project for all exterior walls of your home in order to achieve the best results.
External Wall Insulation Components
A complete EWI system consists of multiple layers of material that provide heat retention, stability, and protection from the weather. There is also the glue and mechanical elements that hold it all together.
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Insulation Material: The actual insulation, usually mineral wool, sheep’s wool, or expanded polystyrene boards.
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Adhesive Layer: A layer of adhesive material that is used to attach the insulation to the wall.
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Mechanical Fixings: The fixings used to attach the insulation to the wall.
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Mesh: A steel or fibreglass mesh will be embedded in the render to add strength to the entire construction.
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Render: A render is applied to the outside of the wrap with your chosen colour and texture. This protects the insulation from rain.
Cost of External Wall Insulation
External Insulation is one of the more expensive ways to insulate your home in Ireland. This is due to the size of the project and how time-consuming it can be to have an EWI system installed.
The median cost of external insulation is between €15,000 and €25,000 for Irish homes, with the average semi-detached house paying just over €23,000. This will depend mostly on the scale of the project.
Source: SEAI data on costs submitted for Better Energy Homes scheme from Jan – June 2025
Grants for External Wall Insulation
Among the SEAI insulation grants is an external wall insulation grant, which is available for the majority of homes in Ireland. The value of the grant you will receive is based on the type of home you live in. The maximum grant for EWI systems is currently €8,000.
Expert Tip: The grant value is fixed to the type of home you live in. That means that if you get a cheaper quote, it can cover a greater portion of the total costs.
Read more in our guide to Home Insulation Grants.
Factors Affecting the Cost of External Wall Insulation
Insulation Material Used: Materials such as mineral wool have a higher material cost per square meter than rigid board insulation. Among solid board insulation, some variants, such as PIR, are more expensive than others.
Property Size: The larger the surface area of your walls that needed to be insulated, the higher the price of the project will be.
Render Type: Some renders, like those mimicking the appearance of brick, are more expensive than simple lime renders.
Types of External Wall Insulation
There are multiple different materials that can be used in external wall insulation, including different types of natural or synthetic ‘wools’, and varieties of solid board insulation. Choosing between them depends on your preference for sustainability, thermal conductivity (K-value), aesthetics, and pricing.
Sheep’s wool is a popular insulation material for being both eco-friendly and very easy to install, coming in large rolls or batts. An all natural material, sheep’s wool is also very breathable, a plus for homes where condensation is an issue.
The major downside of sheep’s wool is that it can be an expensive choice, and it doesn’t have as strong a thermal performance as some synthetic alternatives.
- Thermal Conductivity: 0.0359 – 0.042 W/mK
Mineral wool insulation, made from melted glass or stone that is spun into fibres, combines strong thermal performance with good acoustic insulation and excellent fire resistance. All of this at a moderate price. It is also completely recyclable and non toxic for the environmentally conscious.
It may need to be laid thicker than solid board insulation in order to achieve the same thermal performance. This could be an issue if you are in a home where substantially increasing the wall thickness is an issue.
- Thermal Conductivity: 0.035 – 0.040 W/mK
PIR boards are a closed-cell solid foam insulation that has some of the best thermal performance of insulation on the market. This means that you can achieve very good results with thin boards, ideal for an external wrap.
Along with other solid board insulation, it is lightweight and can be cut and shaped easily. It is also somewhat fire resistant, but not to the same extent as mineral wool.
Thermal Conductivity: 0.022 – 0.028 W/mK
XPS is a closed-cell extruded polystyrene insulation that offers a good balance between the high performance of PIR boards and the affordability of EPS solutions. It has good thermal resistance properties with relatively thin boards.
Thermal Conductivity: 0.028 – 0.038 W/mK
Expanded Polystyrene (EPS) is a lightweight insulation material that is 98% air, making it easy to handle and cut. This also means that it’s thermal performance should remain largely the same across it lifespan, compared to other insulations that may degrade over time.
Thermal Conductivity: 0.030 – 0.040 W/mK
Wood fibre insulation is made from compressed wood chippings for a material that is easy to source, and completely environmentally friendly. It is also vapour permeable and hygroscopic, reducing the need for vapour control.
It is also a compressible material, unlike synthetic boards, which can help in getting a tight fit. However, wood fibre does have a lower thermal performance than other materials.
Thermal Conductivity: 0.040 – 0.060 W/mK
Benefits of External Wall Insulation
A Warmer Home
External Insulation provides a complete wrap of your home’s wall to trap heat, making it easier to keep your home warm.
Reduced Energy Bills
Insulated walls can reduce heat loss in your home by up to 30%, saving hundreds of euro a year on energy costs.
Reduced Noise
Insulation such as mineral wool provides excellent acoustic insulation, reducing the amount of outside noise getting in.
Lower Carbon Emissions
Reducing the energy needed for heating can significantly reduce your carbon footprint by using less gas, oil, or electricity.
Improved Appearance
If your home has a weathered and ageing appearance, then external insulation and its render can give it a facelift.
Higher Property Value
Insulating your home will significantly increase the value of the property, with a better BER and lower bills for buyers.
Weather & Draughts
An airtight insulation wrap will reduce draughts and also protect your home from potential rain ingress.
Planning Permission for External Wall Insulation
External Wall Insulation is more likely than other forms of home insulation to require planning permission. This is due to the fact that the work takes place on the outside of the building and is more visible. Whether planning is required will depend on the following factors:
Material Alteration: How much has the appearance of the building been changed by having the external insulation installed?
Neighbourhood Appearance: Does your home match the appearance of other homes in the area, or does it appear different to them afterwards?
Protection of the Building: Is your home a protected structure or located in an Architectural Conservation Area? These have extra statutory requirements for any work done.
Local Authority Rules: Different local authorities will have differing requirements for building designs. These can also vary within a county based on Local Area Plans.
The simplest way to tell if you need planning permission for external wall insulation, or if it is allowed at all, is to ask your local authority.
How External Wall Insulation is Installed
External Insulation is a larger project than most other forms of insulation work, and can take several weeks to complete in total. There are complicated elements that come from working on the outside of a home, and the different layers can take time to dry. There is also the sheer scale of the project, which typically covers a larger area than other insulation work.
- 1Assess the Condition of the Wall: First, the walls that are being insulated must be assessed to see of there are any serious issues with cracking, damp, mould, mildew, or structural damage that needs to be prepared first.
- 2Test the Wall Integrity: Test the integrity of the existing render or wall structure to ensure that it is capable of supporting the weight of the insulation once it is in place.
- 3Ensure the Wall is Level: Test the line of the wall to see that it is level enough to fix the insulation to without leaving any air gaps. Apply a leveling coat anywhere it is needed.
- 4Remove External Features: Remove or reposition any external features such as drainpipes, electrical wiring, broadband and telephone lines, baskets, or lighting that will get in the way of applying the insulation. Live power lines should not be repositioned by anyone except the power company, or at their specific direction.
- 5Protect Windows: Ensure that your windows are protected from any potential damage during the installation phase of the work.
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Fixing Insulation to the Wall: Your chosen insulation will be fixed to the wall with two methods. First, adhesive should be applied to the rear of the insulation boards of batts to ensure that it sticks. Once the insulation is in place, mechanical fixings are applied to ensure that it will remain securely in place.
- 2Ensure Insulation is Level & Sealed: After the insulation has been applied you must ensure that it forms a level surface for the best results. Adhesive or dubbing out redners can be used to correct any leveling. Any gaps between the insulation boards should be filled with expanding foam to create a full seal.
- 3Apply Base Coat: A base coat of render is applied to the outside of the insulation. This is typically a polymer-modified cement 3mm – 6mm thick, or a traditional render 20mm – 30mm thick. The base coat should only be applied when the weather is expected to remain dry for 48 hours.
- 4Add Reinforcing Mesh: The reinforcing mesh should be applied at the same time as the base coat layer. The mesh should be pushed into the base coat to keep it in place. A second layer of base coat will then be applied on top of it until the mesh is no longer visible.
- 5Final Finishes: Once this is done, your selected final render should be applied on top of the base coat to provide further weatherproofing and the desired appearance of your walls afterwards. This will be 1mm – 10mm thick, depending on the material used and the selected appearance.
- 6Beads, Trims, and Flashings: Any beads and trims required for the junctions and closers of the external wall insulation system should be installed as per the manufacturer’s recommendations.
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Windows and Roofs: After having the insulation installed, your windows will need new sills installed, and the overhang of the roof may also need to be extended. This is due to the greater thickness of the wall with insulation added. These need to be of a depth great enough to ensure that any water runoff does not fall onto the insulation.
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Reinstall Fittings: Any pipes, wiring, or other external fittings removed during the process should be reinstalled, with extensions as needed to match the new wall thicknesses.
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Inspecting & Surveying: An inspection of the work will be carried out to ensure that the installation has been done to acceptable standards, and that the final appearance of the EWI matches what the homeowner wanted.
Fully Insulate Your Home
Alongside external wall insulation, the other areas in your home that need to be addressed for it to be fully insulated are the attic and the floor. With the walls, roof, and floor insulated, you should have a full seal against heat loss.
FAQs
External wall insulation can have a lifespan of more than 30 years if it is installed and maintained properly. It is meant to last for the entire life of a property.
Yes, you can still get mechanical fittings for baskets, satellite dishes, etc., on the outside of your house after getting external insulation. However, you will likely have to drill through to the wall proper to ensure that the fitting can take the required weight.
Yes, your external wall insulation should be inspected annually to ensure that it is in good condition, that all sealants remain, and to look for any damage that should be repaired to prevent water ingress.
Yes, your walls will become thicker after installing EWI. The exact increase in thickness will depend on how much insulation is used and the render finish.
No, external insulation (EWI) must be done on the entire building as it is classified as a ‘major renovation’ and subject to specific requirements under the Building Regulations.
