What is Cavity Wall Insulation?

Many homes in Ireland and the United Kingdom are built using cavity wall construction, meaning there are two brick or block walls with an air gap in between (an air gap between the inner and outer leaf). While many newer homes are built with adequate levels of insulation, many older homes built using a cavity wall construction may contain no insulation at all. 

Cavity wall insulation completely fills the air gap between the inner and outer leaf while still allowing the walls to breath. A wall cavity completely filled with insulation will reduce the amount of heat lost through the walls, resulting in lower energy bills and an increase in comfort for the home's occupants.

What is Cavity Wall Insulation Made From?

KORE Fill cavity wall insulation is made from expanded polystyrene in bead form. Each bead contains 98% air and 2% carbon and hydrogen and is roughly 3 to 8mm in size.

How is Cavity Wall Insulation Installed?

KORE Fill may only be installed by certified and approved KORE Fill installers. KORE Fill bead is injected along with a bonding agent through the exterior walls of the structure. The bead along with the bonding agent solidifies and forms an insulating mass that significantly reduces the thermal transmittance across the cavity.

Holes approximately the size of a one Euro coin (22mm to 26mm) are drilled in an approved pattern along each of the exterior walls. These holes are normally spaced 600mm to 650mm apart horizontally and 200mm above the highest ceiling level.  Two-storey buildings are also subject to a further series of holes space 2m apart drilled at the middle height to ensure a complete fill. The cavity wall bead is then pumped (with compressed air) in using specialised equipment provided by the installer. The drilling pattern ensures that the cavity of the wall is completely filled with bonded bead. After the walls have been pumped, the holes are filled with mortar and coloured to match the existing appearance of the home. 

How Long Does it Take to Install?

Depending on the size of the home cavity wall insulation can usually be installed in one day. Larger homes or inclement weather may cause delays. All equipment and material is removed from the job site at the end of each working day. Since installation occurs from outside the home there will be minimal disruption to occupants. Any leftover material is cleaned up and removed from the site at the end of each day and once works are complete.

Are All Homes Suitable for Cavity Wall Insulation?

There are a number of home insulation systems available on the market. Cavity wall insulation is only suitable for houses constructed with a wall cavity made from block or brick. Timber or steel framed houses, hollow block, cavity block and solid block walls are not suitable for bonded bead cavity wall insulation. The wall cavity must be at least 40mm wide and free from defects and debris. There must be no signs of dampness on the inner leaf and mortar joints must be in good condition and free from defects which may allow water ingress.

The home's exposure is also taken into consideration (wind-driven rain). Normal exposure is considered 5m2/sec/year, while severe exposure is classified as above. Building sites may need to be assessed individually for classification as normal or severe exposure. Unrendered brickwork is not suitable for full fill cavity wall insulation in severe exposure zones.

An on-site survey is performed on every structure before the installation of KORE Fill Bonded Bead. This survey includes the use of a borescope to examine the internal wall structure. Every assessment will include:

  • Form of construction and site conditions
  • Age of the building
  • The structural condition of the building
  • The size of the wall cavity
  • The structure's exposure to wind-driven rain 

Existing home ventilation must also be assessed. This includes ventilation openings that provide combustion air, underfloor ventilation and flues in the cavity wall. Adequate sleeving must be present on all ventilation to ensure that these openings do not become blocked by the insulation. Structures with inadequate ventilation will need remedial works to meet the requirements of Part F of the Building Regulations before works begin.

Are All Insulation Installers Approved to Install Bonded Bead?

No. KORE has a nationwide network of approved and certified KORE Fill Bonded Bead installers which can be found on the Official KORE Fill Installers Register. All our installers are:

  • Registered with the NSAI Agrement CWI Scheme
  • Approved by KORE and NSAI to install KORE Fill Bonded Bead
  • Trained and registered with KORE to survey and install the product
  • Required to carry ID cards certifying the above
  • Supervised by KORE and subject to unannounced quality audits

While our network of installers are approved to install KORE Fill cavity wall insulation, many offer additional products and services in home insulation and energy efficiency. Check directly with your local installer for a full list of products and areas covered. Some installers may offer a nationwide service area.

What Other Measures Should be Installed with Cavity Wall Insulation?

Cavity wall insulation is just one product designed to help increase a home's energy efficiency, reduce heat loss and running costs. Other measures should be installed alongside CWI to complement these benefits:

  • Attic insulation or loft insulation to a depth of at least 300mm or the use of an insulated attic flooring system
  • Proper roof and wall ventilation to increase the availability of fresh air and reduce moisture and condensation (e.g. tile vents, slate vents, soffit vents, mechanical vents etc.)
  • Draught proofing measures around windows, doors and letterboxes
  • Low energy light bulbs to reduce electricity consumption
  • Servicing on oil or gas-fired boilers, including power flushing of the existing heating system
  • The implementation of renewable energy sources like solar water heating systems, heat pumps and biomass boilers whenever possible 

Homeowners may have a Building Energy Rating assessment performed after new home insulation and energy efficiency measures are installed. A home with a good BER rating can increase property value by as much as 10%.

Will the Insulation's Performance Decrease Over Time?

KORE Expanded Polystyrene is made from a sustainable, durable and long-lasting material. In fact, EPS insulation should outlast the life of the building. It is water resistant and will still allow the wall cavity to breath as originally intended. Any water that does penetrate the outer leaf of the structure will drain through the bottom of the cavity without affecting the insulation, unlike mineral wool or rockwool. Any interstitial condensation (condensation that forms within the interior of the wall) will evaporate during the summer months. Typical construction details and condensation risk analysis are available by contacting our technical team.

What if the Wall Cavity Already Contains Insulation?

Partially filled cavity walls may still be suitable for KORE Fill Bonded Bead. Some cavity walls may already contain rigid expanded polystyrene, foil faced Polyisocyanurate (PIR) or Phenolic board that partially fills the cavity. A minimum cavity width of 40mm is still required to ensure the bead installs correctly. Bonded bead should not be installed in cavities with poorly installed partial fill insulation (e.g. installations that are prone to thermal looping) or cavity walls that contain mineral (glass/wool) boards. KORE Key may also be considered for partial fill applications (combination of partial fill cavity wall insulation and internal wall dry lining).

What U-Values Can I Expect to Achieve?

The U-value is only limited by the width of the existing cavity. For new buildings, the wider the cavity the lower the U-values you can expect to achieve. More information on U-values and technical information can be found in our KORE Fill Wall Insulation Design Guide and Declaration of Performance for KORE Fill Bonded Bead.

Is CWI Suitable for a Semi-Detached Home?

Yes. Cavity wall insulation can be installed in a semi-detached home. A brush is put in place during installation to prevent bead from entering the neighbouring wall. When the bead solidifies the brush can be removed.

Is KORE Fill CWI Expensive?

Any type of insulation upgrade is an investment, but cavity wall insulation tends to be more affordable over external wall insulation or internal wall dry lining. There are several grants available to help reduce the cost: SEAI's Better Energy Homes Scheme and KORE's Energy Efficiency Incentive. The cost of installing cavity wall insulation mainly depends on the size of the structure. You'll usually pay less in labour costs as the installation of bonded bead can be installed over the course of a day or two. External wall insulation and internal wall dry lining typically take 7 to 10 days, again depending on the size of the structure and environmental and site factors.

Are There Grants for Cavity Wall Insulation?

Yes. The Sustainable Energy Authority of Ireland (SEAI) offers grants under the Better Energy Homes Scheme for homes built before 2006. The grant offers €300 towards cavity wall insulation and €300 towards attic insulation or loft insulation. You may also qualify for an electricity bill or gas bill discount depending on your provider. Learn more about the grants available for home insulation works.   

Is Moisture or Condensation a Problem with CWI?

You may have heard about moisture, damp or mould problems with cavity wall insulation. These problems will not occur with properly installed KORE Fill Bonded Bead. Ensure you only use a certified and approved KORE Fill installer for any works. The house will be surveyed to ensure it is suitable for cavity wall insulation before any works begin. The home will also need to be properly ventilated in accordance with Part F of the Building Regulations. This includes roof ventilation, wall ventilation and mechanical ventilation. Ventilation will need to be installed or upgraded before the installation of bonded bead. The exposure zone of the home will also be taken into consideration during the initial on site survey.

KORE Fill does not degrade over time. The product is water resistant and will not affect the cavity's ability to breath. You can verify if a company is approved to install KORE Fill by visiting our Official KORE Fill Register or by contacting us directly. 

How Long Does it Take to Start Working?

KORE Fill Bonded Bead will start working immediately. You should notice your house is warmer and retains heat for longer periods of time from the day it is installed. Our installers will verify your heating system is working correctly and that the cavity wall insulation has not blocked any ventilation before they leave the job site.

Does Cavity Wall Insulation Require Maintenance?

No. Cavity wall insulation does not require any maintenance once the product is installed in your home. You should continue with your normal home maintenance routine, however. Cavity wall insulation will never have to be removed or 'topped up' once it's installed. 

Can I Obtain a Quotation Over the Phone?

No. You'll have to schedule an on site visit to your home for an accurate quotation and to ensure your home is suitable for cavity wall insulation. If not, you may choose to have your home insulated with another system. 

KORE does not install bonded bead. We have a nationwide network of installers who would be glad to offer you a quotation directly. You can view a list of KORE Fill installers by region here.

Is KORE Fill Suitable for New Builds?

Of course! Bonded bead is perfect for new build applications that have been constructed with a wall cavity. You can learn more about KORE Fill for new build applications by downloading our Cavity Wall Insulation Design Guide, including example U-values dependent on construction type and cavity width. You can contact our technical team directly for condensation risk analysis and typical construction details. 


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