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Cavity wall insulation costs roughly between €7.50 - €10.50 per m2, and for a standard three-bedroom house, the cost is about €1,900 - €2,200. There are SEAI grants available for cavity wall insulation up to €1,700 depending on the size of your home. Cavity wall insulation involves filling the cavity between your inner and outer walls with an insulating material that will help your home to become more energy efficient, reducing the amount of heat that is lost through your exterior walls.
Cavity wall insulation is when a material is used to fill the space in between the two “skins”.
The material inserted can be, but is not limited to:
Most modern buildings are already built with insulated cavity walls, but older buildings do not. Almost a third of heat lost in uninsulated homes escapes through the walls.
Small holes are drilled at gaps of about 1 metre in the wall, and the insulation is injected through the holes. The holes are then sealed with cement or white putty.
Installers are normally careful in their placement so as not to destroy the aesthetic of your house, but you can always touch up the filled-in holes with paint to match the surrounding walls.
The main aim of this type of insulation is to reduce heat loss that may occur when the cavity between the skins is empty. Filling the space in a cavity is done to reduce the possibility of convection.
By removing the possibility of air moving around between the two leaves of a wall, convection can be greatly reduced or even eliminated. To what degree depends on the quality of material used. The less air that is able to circulate, the less heat that can be lost.
It is a simple process which will only take around two hours. We do not recommend doing it yourself, due to the potential to cause structural or cosmetic damage to your outer walls.
There are two main varieties of cavity wall insulation:
The type of insulation material best suited to your house will depend on whether it is a new build or retrofit project.
Pumped insulation is typically more suited to retrofit project, as there is minimal interference with the fabric of cavity wall.
The main varieties of insulation materials used on cavity walls are:
For insulating existing cavity walls, a common method is 'pumped' insulation. This involves injecting insulation material through small holes drilled in the outer wall.
It's generally preferred for retrofits because it's less invasive, making it a faster, more affordable, and less disruptive option for homeowners.
There are different types of pumped insulation available:
For solid cavity wall insulation, the common materials are usually rolls or batts of mineral wool, or rigid boards of polystyrene. These can offer excellent thermal performance, particularly in new construction.
However, when it comes to insulating an existing house, these methods are less frequently used because they typically require more construction work around the cavity walls.
The cost of cavity wall insulation varies widely depending on several factors, but you can generally expect to pay between €7.50 and €10.50 per square meter.
For an average three-bedroom semi-detached house, the total cost typically ranges from €1,900 to €2,200. The final price is determined by the specific characteristics of your home and the chosen insulation material.
Several key factors will influence the final cost of your cavity wall insulation project:
The table below provides a more detailed estimate of the cost for different types of properties. These are average prices and should be used as a guide only.
| Property | Estimated Wall Area (m²) | Average Cost per m² | Estimated Total Cost |
|---|---|---|---|
| Apartment | 70-100 | €8.50–€10.50 | €600–€1,050 |
| Two-Bed Semi-Detached House | 120-150 | €1,020–€1,575 | |
| Three-Bed Semi-Detached House | 180-220 | €1,530–€2,310 | |
| Four-Bed Semi-Detached House | 250-300 | €2,125–€3,150 |
The prices above are estimates and do not include any SEAI grants. You should always get multiple quotes from different contractors before making a final decision.Source: Energyefficiency.ie
Do I Need Planning Permission for Cavity Wall Insulation?
No. Planning permission is not required for cavity wall insulation however if your home is a protected structure or in a conservation area, you should inquire with your local council before commencing with your insulation work.
The SEAI is offering grants for cavity wall insulation to all homeowners. The grant amount is dependent on the size of your property but range from €700 for apartments, to €1,700 for detached homes.
The grant is only available for homes that were built and occupied before 2011.
To apply for a wall insulation grant, you can apply online via the Individual Home Energy Upgrade application portal.
| Property Size | Grant Value |
|---|---|
| Apartment (Any) | €700 |
| Mid-Terrace House | €800 |
| Semi-Detached/End-Terrace | €1,200 |
| Detached House | €1,700 |
How Much Money Can Cavity Wall Insulation Save You?
Keep in mind that by installing insulation you should also be able to save up to €300 a year off your heating bills, so view cavity insulation as an investment that will pay off after just a couple of years.
There are several benefits to having your wall cavities insulated, from saving on energy costs to improving the value of your property.
Some benefits include:
In order to find a contractor that both suits your needs and budget for your home cavity wall insulation project, we recommend following these steps:
While cavity wall insulation offers significant benefits, it's important to be aware of potential issues that can arise from poor installation.
We do not recommend carrying out the insulation process by yourself, Cavity wall insulation requires specialist equipment and trained personal to make sure it is done correctly to avoid any long term issues.
Most houses built after the 1940s in Ireland have cavity walls.
You can check the thickness of your external walls (if they are more than 260mm thick, it is likely a cavity wall) or look at the pattern of the bricks (if they are laid lengthways in a simple alternating pattern, it is likely a cavity wall).
Dampness can occur, but this is generally due to poor installation as opposed to a downside of the insulation itself.
Walls that are in an area of the house that have wind driven rain should be insulated with bonded beat insulation to allow any water that permeates to trickle down.
Done properly, cavity wall insulation should last the entirety of the lifetime of the building.
Read More of Our Home Heating Articles
The services and products mentioned on this website may only represent a small selection of the options available to you. Selectra encourages you to carry out your own research and seek advice if necessary before making any decisions. We may receive commission from selected partner providers on sales of some products and/or services mentioned within this website. Our website is free to use, and the commission we receive does not affect our opinion or the information we provide.
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