Cavity Wall Insulation: Guide and Price
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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 costs roughly €7.50 - €10.50 per m2 and for a standard, three-bedroom house, 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.
What Is a Cavity Wall?
A cavity wall is a type of wall that is hollow in the centre. The wall material on either side of the cavity is often referred to as “skins”, or “leaves” and is usually made of bricks or blocks. You can normally tell if your home has cavity walls or not by looking at any section of exposed brickwork on the outside walls.
If all the bricks are laid evenly lengthways in a simple alternating pattern, you have a cavity wall. If, however, you can see the ends of some bricks as they have been laid widthways, then you have a solid wall. Solid walls are rare nowadays and are usually only found with pre-1920’s properties.
If you cannot see any exposed brickwork then measure how wide your external walls are. Walls more than 26cm thick are most likely to be cavity walls.
What Is Cavity Wall Insulation?
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:
- Glass wool
- Rock wool
- Cellulose
- Foam
- Polystyrene beads
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.
How Does Cavity Wall Insulation Work?
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.
How Much Does Cavity Wall Insulation Cost?
The exact cost of your cavity wall insulation will depend on various factors including:
- The size of your home
- The width of the cavity
- The type of insulation material
- Accessibility
- Labour costs
Simply put, the more space that needs to be filled, the more the insulation will cost, but you can expect to pay between €7.50 - €10.50 per m2.
The table below provides a rough estimate of the cost of cavity wall insulation for different sized properties:
| Property | Estimated Cost |
|---|---|
| Two-Bed Semi-Detached House | €1,500–€1,900 |
| Three-Bed Semi-Detached House | €1,900–€2,200 |
| Four-Bed Semi-Detached House | €2,200–€2,600 |
Source: Energyefficiency.ie
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Are There Grants For Cavity Wall Insulation?
The SEAI are 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.
| Insulation Type | Property Size | Grant Value |
|---|---|---|
| Cavity Wall Insulation | 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.
What Are The Benefits of Cavity Wall Insulation?
There are several benefits to having your wall cavities insulated from saving on energy costs to improving the value of your property.
Some of the benefits include:
- Cavity Wall Insulation Benefits
- Heating Bills - Proper wall insulation can significantly reduce the heating bill for a home.
- Environmentally Friendly - Reduces the amount of energy you need to heat your home.
- Noise Reduction - Lowers the amount of noise you hear from inside your home while working.
- Heat Retention - Makes your home more comfortable especially during colder months.
- Higher Property Value - Well insulated walls help increase the BER rating of your home.
- Energy Neutrality - Can help as part of a passive house.
- Combine with a heat pump - together with a heat pump and other energy saving appliances you can further lower your bills
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 enquire with your local council before commencing with your insulation work
Are There Any Drawbacks to Cavity Wall Insulation?
Overall, we can say that there are no negatives to having your cavity walls insulated. It offers a relatively cheap means of insulating your home to improve its heating efficiency and lower your energy bills.
Potential damp problems can arise from bad installation or poor understanding of your property.
If a house has a brick wall in an area with wind driven rain there is a possibility of moisture permeating through solid insulation. Bonded bead insulation solves this by allowing water to trickle down through the honeycomb. Properly installed cavity wall insulation should help to prevent damp in most environments.
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