Keep windows closed
and external doors firmly shut to prevent dust from entering.
Why get wall insulation?
Home insulation is probably the single most effective upgrade in terms of creating a warmer, more comfortable home and reducing energy bills long term. Who wouldn’t say yes to a warmer house and lower bills?
According to the SEAI, homes lose 20-30% of their heat through the walls if not properly insulated, which makes your house cold, increases your energy bills, and increases your carbon footprint.
When you weigh up the initial cost with the lifespan of insulation, it’s a very cost effective and long lasting option for upgrading your home. The upfront investment is a small price to pay for such a good deal – it’s a no brainer!
What is a cavity wall?
Cavity wall houses are built with two thin walls (usually brick), with a gap between them (the cavity), which is held together by metal wall ties. Cavity walls were originally Just as clothes trap a layer of air to keep you warm, the cavity wall system traps air to keep the house warm.
At the time they were originally invented they were a better alternative to single leaf walls, which consistently caused problems with damp in the house. The cavity was much more effective at preventing damp, however, as awareness has increased about environmental issues, we’ve discovered more effective ways to insulate walls.
What is cavity wall insulation?
Cavity wall insulation is insulating material that goes in between the two layers of a cavity wall to prevent heat being lost through the walls. Most commonly made from small polystyrene balls or foam, the insulation is injected through small, minimally invasive holes in the wall. The insulation improved the insulating capacity of the cavity and, when properly installed, also continues to prevent damp from entering the home.
Please note that cavity wall insulation is not the only option for cavity walls. External wall insulation can also be used on cavity walls and more and more homeowners are choosing this in addition to CWI as it is far more effective than cavity wall insulation alone. Visit our external wall insulation page for more details.
Does my house have cavity walls?
In Ireland, most houses built before the 1950s had solid walls. Cavity walls were introduced from the 1950s onwards. In the 1990/2000s, cavity wall insulation was introduced, so homes built from the 1990s onwards may already have some insulation in the cavity.
Take a look at the walls of your house from the outside. If the bricks all look the same length, most likely you have cavity walls. If some of the bricks appear shorter in length, they have been placed end on, and you likely have solid walls.
If you have cladding or rendering, check the thickness of the wall, if it’s more than 260mm thick, it may well be a cavity wall.
If you don’t have cavity walls
You can still get insulation if you don’t have cavity walls, you just need a different type of insulation. External wall insulation is very popular with our clients, and suitable for most solid wall homes. LINK
Are the walls already insulated?
Even if you’re struggling with cold or damp inside the house, your cavity walls may already be filled with insulation. Poorly installed cavity wall insulation can cause problems inside the house, so don’t assume that it isn’t already there.
Look at the outside walls of your home and look for marks on the walls at 1 inch intervals. If cavity wall insulation was previously installed, there will be signs of tiny holes that were used to install the insulation. Even though the holes will have been filled, you should still be able to see slight marks there.
You can also check your attic – you may see cavity insulation coming out of the top of the wall, although this is not a good sign – contact us to fix it for you.
If you’re in any doubt, this is something we can check in our free consultation.
Benefits of cavity wall insulation
The walls are a major area of heat loss in houses, so cavity wall insulation is effective at reducing this heat loss, resulting in a warmer house through the winter. But don’t worry about getting too hot in the summer – the insulation will help to keep the house cool in hot weather.
If you’ve been spending a fortune on your heating and still struggling to stay warm, you’re definitely going to see a difference in your energy bills. And with cavity bead insulation and foam insulation both having a long lifespan, it’s very cost effective.
You’ll also see an improved BER rating, which increases the value of your property, and reduce your carbon footprint at the same time.
Is it worth it?
According to the Energy Saving Trust, cavity wall insulation usually pays for its full cost in 5 years or less. However, with good grants available from the SEAI, you could knock a year or more off this.
Of course, the actual payback time depends on a number of factors. If you’ve had the heating on non stop to try and keep your home warm, and your bills are high, you’ll see great savings. If you’ve been avoiding putting the heat on to keep costs down, then you won’t see such high savings, but you’ll have a vastly warmer house at a lower cost.
And if you get your insulation installed right before the winter, you’ll start seeing the cost savings instantly, where spring installations will have to wait a few months to see the biggest changes in their bills.
Should I get cavity wall insulation?
Yes if:
- You have unfilled cavities made of brick
- Cavity is at least 50mm wide
- Brickwork is in good condition, no cracks in the walls (minor cracks can be fixed before installation)
- External walls are accessible (if house is semi detached or terraced, you’ll need a cavity barrier which increases costs)
- Be aware that garage, conservatory, or extension may not be suitable for cavity insulation
- Home is less than 12m high
- Internal walls are dry – if you have damp, you should get this remedied before cavity insulation
- There is adequate ventilation
- Walls are not regularly exposed to driving rain as they have difficulty keeping the moisture out which damages the effectiveness of the insulation
- House does not have steel or timber framed construction (you’ll see this in the attic where you’ll see the party or gable walls made of timber)
Book in for a free consultation and we’ll be able to advise you on the best type of insulation for your home.
Types of cavity insulation
The most popular type of cavity wall insulation is polystyrene beads. This is a very efficient type of insulation and the most easy to install, especially with hard to reach areas. You may have heard about issues of leakage with this type of insulation, but in recent years these have been overcome by the use of a special adhesive. Performance is not as good as foam and not as environmentally friendly as mineral wool.
Polyurethane foam is also popular as it is a very effective insulator, very fast to install, creates an airtight seal, and has the additional benefit of extra soundproofing. This is the most expensive option, best for cavity walls with hard to reach areas or uneven cavities, or if the property is in a flood risk area.
Mineral fibre wool is less commonly used. It is a loose wool that is blown into the wall. It is cheaper, but can settle over time, becoming inefficient, and if it gets wet, it loses its insulating properties. It is the most environmentally friendly, with little environmental impact and can be recycled afterwards if you need to get it replaced.
The best type of cavity wall insulation for your home depends on your house and your budget. We can advise you as to which is the best choice for your house at your free consultation.
How to choose cavity wall insulation
It’s best to get an insulation specialist to visit and inspect your home. They can advise you on whether your house is suitable for cavity wall insulation, and if so, which type.
Ensure that your insulation contractor uses materials that reach the required performance standards. Insulation performance is measured by U-value, which measures how much heat is conducted through the insulation. A low U-value means little heat passes through the material, so your house will stay warm longer. To qualify for an SEAI grant, wall insulation must achieve a U-value of 0.27W/m²K or lower.
You should also check that your service provider is registered with the NSAI and that the insulation itself is NSAI Agrément certified.
What to Expect During Installation
Getting Ready
Before installation begins, we recommend taking a few simple steps to prepare your home:
Cavity wall insulation can usually go ahead in most weather conditions. Only very heavy rain or extreme cold may delay the job — we’ll keep you informed if rescheduling is needed.
On the Day: The Installation Process
Every installation starts with a final check by our technicians. Depending on the insulation system being installed — bonded bead or spray foam — the process will vary slightly, but always follows rigorous technical and safety standards.
Here’s what typically happens:
- Cavity inspection: We confirm cavity width, wall condition, and suitability before beginning. Any issues with damp or wall structure are flagged and addressed first.
- Ventilation check: We inspect existing vents. If any underfloor vents aren’t sleeved, we’ll remove them, install proper sleeves, and replace the covers to maintain airflow.
- Boundary protection: Where your home shares a wall with another property, we install a vertical cavity barrier to contain the insulation material within your boundaries.
- Precise application:
- For bonded bead, we follow an IAB-approved drilling pattern and inject high-performance polystyrene beads mixed with adhesive to form a stable, solid fill.
- For spray foam, we access the cavity via fewer, wider entry points and apply the foam in expanding layers to achieve a full, continuous insulation seal.
- Finishing work: Once filled, all drill holes are carefully sealed with colour-matched mortar. Any access points are sealed, and chimney flues (if present) are tested to ensure they remain clear.
Clean, Quick and Low-Disruption
Most cavity wall insulation jobs are completed in a single day. Work is carried out externally, so there’s very little disturbance inside your home — apart from occasional attic or smoke tests, if needed.
There may be a small amount of dust during drilling, and with bonded bead, a few loose beads may escape — this is completely normal and quickly cleaned up. We always power wash and tidy the area before we leave, leaving your home as clean as we found it.
How to find a good service provider
Check that your service provider is on the SEAI register, certified by NSAI, registered with NIAI, that products are IAB, NSAI, or BBA certified, and that they have full liability insurance.
Your insulation will only be guaranteed if installed by a fully qualified professional.
Give more detail on how grants work
We discount grants up front!
The SEAI offers grants towards the cost of your home insulation. This is part of Ireland’s efforts as a nation and a member of the EU to reduce emissions and combat climate change.
You apply to the SEAI for your grant, and once the work has been completed, and your application has been approved, the grant will be paid. But we’re so confident in the quality of our work that we discount the value of the grant off your bill in advance! Win win.
If you have a heat pump you might be better with EWI
Heat pumps require a well insulated house in order to reach maximum efficiency. Cavity wall insulation often does not reach the same level of effectiveness as external wall insulation (EWI), so EWI is a much better choice for use with a heat pump. When your house is well insulated with EWI, your heat pump will work at maximum efficiency, and often you’ll only need to switch it on in the coldest months of winter.
Contact us today to find out if your home is suitable for EWI.
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