Cavity Wall Insulation

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Cavity wall insulation is a method used to improve the thermal efficiency of buildings with cavity walls. Cavity walls are constructed with two layers (or "skins") of brick or concrete block, separated by a hollow space (or "cavity") between them. This cavity can be filled with insulating material to reduce heat loss, thereby enhancing energy efficiency and reducing heating and cooling costs. We stock a range of boards and slabs (both partial fill and full fill) from industry-leading manufacturers like Celotex, Knauf Insulation, and EcoTherm

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What Is Cavity Insulation? 

Cavity insulation refers to insulation material that is placed within the inner and outer leaves of unfilled cavity walls. If uninsulated, masonry cavity wall construction can be a major culprit of heat loss, compromising the thermal envelope of a building structure. 

Having cavity wall insulation installed is a smart, energy-conscious choice which will ultimately benefit the thermal performance of your masonry cavity walls. 

Please note: Installing cavity wall insulation is a technical procedure that requires the help of a professional. It's important to choose a reputable installer who is registered with a recognised body, such as the Cavity Insulation Guarantee Agency (CIGA). This ensures that your installation is covered by a guarantee, providing peace of mind and protection against any potential issues.

What is a Cavity Wall?

A cavity wall consists of two layers of brick or concrete blocks separated by a gap (or cavity). These walls were commonly built in houses constructed from the 1920s onwards. The cavity is designed to prevent rainwater from penetrating the interior walls and to improve thermal insulation.

Identifying Cavity Walls in Your Home

A cavity wall is made up of two slender walls that are connected by wall ties, leaving a space in between them.

To find out if you have cavity walls, inspect a window or door along an external wall: If the brick wall measures over 260mm in thickness, it likely features a cavity. A narrower wall is more likely to be solid.

If your house is constructed with stone walls, it's probable that they are solid, without any cavities that can be insulated. In such instances, you may want to go down the route of external insulation.

We stock a wide range of External Wall Insulation (solid wall insulation) solutions for projects that are not suitable for cavity wall insulation. 


Why Insulate Cavity Walls? 

  • Energy Efficiency: Proper insulation significantly reduces heat loss, which can lower your energy bills by up to 35%.
  • Comfort: Insulated walls help maintain a consistent indoor temperature, enhancing the overall comfort of your home.
  • Environmental Impact: Reducing energy consumption decreases your carbon footprint, contributing to environmental conservation.
  • Preventing Dampness: Insulation can help reduce the risk of condensation and dampness within the walls, protecting the structural integrity of your home.


Signs Your Home Needs Cavity Wall Insulation

  • High Energy Bills: If your energy bills are unusually high, it could be a sign that your home is losing heat through uninsulated walls.
  • Cold Walls: If the interior walls of your home feel cold to the touch, it may indicate poor insulation.
  • Damp and Condensation: Uninsulated walls are more prone to damp and condensation issues, which can lead to mould growth and structural damage.


Types of Cavity Insulation

There are various methods of insulating cavity walls. However, we specialise solely in stocking cavity wall insulation slab and board solutions. These materials are designed to fit perfectly within the wall cavity, providing an effective barrier against heat loss. Here are the common types we offer:

  • Insulation Slabs: Insulation slabs are rigid slabs manufactured from either glass wool, rock mineral wool or sheep’s wool. They provide excellent thermal performance and are easy to install.
  • Insulation Boards: Similar to slabs, insulation boards can be made from various insulating materials and are cut to fit snugly within wall cavities.

Cavity Barriers

In addition to insulating cavity walls, it is important to consider the use of cavity barriers. A cavity barrier is an essential component in construction that helps prevent the spread of fire and smoke through the cavities of a building. 


Cavity barriers are typically installed in the cavities between the external and internal walls, providing an extra layer of safety and ensuring that the insulation not only improves energy efficiency but also contributes to the overall fire safety of the building.


Frequently Asked Cavity Wall Insulation Questions

How Much Does Cavity Insulation Cost?

Cavity wall insulation can be quite a costly procedure as you not only have to buy thermal insulation but you also have to pay an installation cost. The overall cost depends on several factors, including the size of your home, the type of insulation used, and the complexity of the installation process. 

How Long Does It Take to Install Cavity Insulation?

The installation process typically takes between 2 to 4 hours for an average-sized home. Larger properties or those with complex wall structures may take longer.

Can I Install Cavity Insulation Myself?

Installing cavity wall insulation is not recommended as a DIY project. It requires specialised equipment and expertise to ensure the insulation is installed correctly and safely. It’s best to hire a professional installer who is experienced in handling cavity wall insulation.


Is Your Home Suitable for Cavity Insulation?

Not all homes are suitable for cavity wall insulation. It's essential to determine if your property meets the necessary criteria. Generally, cavity wall insulation is suitable for:

  • Homes with unfilled cavity walls.
  • Homes with easily accessible walls where insulation can be installed.
  • Properties with brick or stone walls that have cavities.


Is Cavity Wall Insulation Fire Resistant?

The fire resistance of insulation materials is measured on the Euroclass scale. This scale was created to regulate the classification of insulation materials in Europe. The scale starts at A1 (non-combustible) and ends at F (combustible).

Different types of cavity wall insulation have different Euroclass ratings.

●     Celotex CW4000 - rated E, partially combustible
●     EcoTherm Eco-Cavity - rated F, combustible
●     Kingspan KoolTherm K108 - rated F, combustible
●     Knauf DriTherm - rated A1, non-combustible

An F rating on the Euroclass scale does not mean that you cannot use these products. All these slabs and boards still provide premium protection against heat transmission. 

If you are concerned about the fire rating of these products, you can simply use a build-up of materials that have better heat protection.

For optimal fire protection, we recommend using a cavity barrier in concealed cavities. Cavity barriers block the passage of fire between cavities, containing the spread of fire to a confined area.

What Are the Different Methods of Filling Cavity Walls? 

Filling cavity walls involves inserting insulating material into the space between the outer and inner walls of a building. This can be done through various methods such as:

  • Blown-in Insulation: Small holes are drilled into the exterior wall, and insulating material is blown into the cavity using specialised equipment.
  • Foam Insulation: Expanding foam is injected into the wall cavity, which then hardens to form an effective insulating barrier.


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