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Meet the Expert: Cavity Wall Insulation Process & Costs - GAR Insulation LTD

Reducing the amount of heat escaping from your home is paramount to reducing energy consumption and energy bills savings.

This month, Ger Reade from GAR Insulation Ltd shares cavity wall and attic insulation processes and cost to reduce heat loss using specialist insulation techniques such as spray foam and polystyrene bead insulation.


OLT: What are the different types of insulation available to homeowners.

Ger: There are three distinct types of insulation solutions currently available.

These are:

  • External Wall insulation
  • Internal Wall Insulation
  • Cavity Wall insulation

External wall insulation is generally applied to single block profile houses where polystyrene slabs are attached to the outer surface of the wall, followed by a special weather-resistant render reinforced with fibreglass mesh. Single-block constructed homes are mostly found in the greater Dublin area.

Internal wall insulation, also known as dry lining, is the process of fixing insulation to the inner walls of a house, followed by a vapour layer and plasterboard. This process of insulation generally results in a property losing internal floor space and is less costly than external.

Cavity Wall insulation is the injection of insulating bead product between the cavity of a double-wall constructed home. Of the three options available, cavity wall insulation is the easiest and the most cost-effective way to insulate your home. However, cavity wall insulation can only be applied to a double-wall build with a gap.


OLT: How can I know if my home is suitable for Cavity Wall Insulation?

Ger: Here are 3 ways a homeowner can investigate if there is a cavity between the internal and external skin of brickwork, known as a double-wall construction.

  1. Measure the distance between the outside and inside wall via a door or window. If the distance is greater than 300mm, then most likely the home has a cavity wall. If it's thinner than 300mm, you are probably dealing with a single block-built home.
  2. If the home's meter box is placed on the outside wall, there may be a gap to look into.
  3. Remove a vent in the wall.


OLT: What is the cavity wall insulation process?

Ger: Before embarking on cavity wall insulation, we carry out a house inspection. An inspection helps us establish if there are any existing insulation boards.

Our first step is to inspect the cavity wall condition using a Borescope and Inspection Camera. This will determine your wall construction.

Cavity walls with partial fill insulation board can still be considered for pumping with bead insulation, with a 30% improvement in heat retention.

Once the cavity walls are deemed suitable, we will schedule a day to start the insulation process, drilling a series of holes on the outside walls and injecting the polystyrene beads, with a pva glue and refill the holes with a sand and cement mix.

The injected product is NSAI approved and bonded with a water-based PVA glue. The bonded product forms a tight seal and stays in place once injected. For example, the beads won't fall out when windows are replaced or rewiring work is done.

Part of the insulation process is installing extra ventilation, particularly in rooms that have solid fuel appliances.

The whole process takes about 6 hours for a semi detached house. There is some noise in the drilling process. The overall benefit is that Cavity Wall Insulation will improve the heat retention considerably in the home.


OLT: Which type of insulation is best for attics?

Ger: GAR Insulation Ltd offers a spray foam insulation service. This form of insulation is not only a cost-effective but is excellent at reducing heat loss through the roof.

Before applying spray foam, a breathable vent card is fitted between the felt and foam, providing a 24/7 airflow for the timbers to breath, and avoid any moisture build-up. The entire process takes approximate 6 hours to install in a semi detached home.

Before we spray foam, we request all items be removed from the attic. We then proceed to cover carpets and floors. While installing the foam ,there maybe a slight vapour build up in the air.


OLT: Is there an SEAI grant for cavity wall and attic spray foam insulation?

Ger: Yes. As of February 8th, 2022, the grants increased to the following values:

Grant Measure

 Grant Value 

Attic Insulation  
Apartment €800
Mid-terrace house €1200
Semi-detached or end of terrace house €1300
Detached house €1500
Cavity Wall Insulation  
Apartment  €700
Mid-terrace house €800 
Semi-detached or end of terrace house €1200
Detached house €1700
BER Assessment  
Max one assessment per home €50


If the homeowner wants to claim the SEAI Grants, they must first apply online before any work is installed.

The cost of a BER assessment is between €200-€350, but by using a registered SEAI contractor, a homeowner can claim back €50 of this expense.

Once the grant is approved, the homeowner has 8-months to get the work done. Post-insulation, a BER assessment will be required to certified the work, after which time the SEAI payment will be deposited directly to their bank account.


OLT: How much does cavity wall insulation cost with the SEAI grant?

Ger: Before the grant, a semi-detach cavity wall insulation service costs approximately €2600 including VAT. Therefore, the net cost to the homeowner is circa €1,400.

Cost for a semi-detach spray foam attic insulation is approximately €3200 including VAT. After receiving the grant, the homeowner will have paid approximately €1,900.

Any homeowner with cavity walls seeking to improve their home energy efficiency rating will be delighted with the results of cavity wall insulation.



GAR Insulation LTD is a SEAI registered, offering expert Cavity Wall and Attic Spray Foam Insulation as well as sound proofing services for domestic and commercial properties.

All customers receive a free consultation with a house or site visit to examine and discuss their individual needs to achieve the maximum return on investment. 

Contact Ger Reade direct on 086-248-9447 or post a job with Onlinetradesmen to find qualified and SEAI registered insulation trade professionals near you.




About the Author


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