Cavity Wall Insulation

Uninsulated walls are the biggest cause of heat loss in any building. With the correct insulation, you can stop 35-40% of heat loss, keep your home warm and reduce your energy bills.

Cavity Walls

Most homes built after 1920 have cavity walls. This means there are two layers of wall – the outer and the inner – with a gap between them. This gap is called the cavity. The cavity is responsible for heat loss. The air in the cavity allows heat to travel through the walls and out of the house.

A diagram showing the structure of a cavity wall. The inner and outer wall are separated by the cavity

What is cavity wall insulation?

To stop the heat from escaping through the walls, the cavity is filled in with insulation beads, foam, or mineral wool. You can think of it like a thermal vest between your skin and a jumper – an extra layer which helps keep the heat in.
To access the cavity, the installer drills small holes into the outer wall. The insulation is then pumped in. Once the cavity has been insulated, the installer will re-fill the holes that were drilled.

Is my home right for cavity wall insulation?

Firstly, you’ll need to check that your home has cavity walls. If your home is less than 100 years old, it’s likely to be the right type of construction.
If you have an Energy Performance Certificate, then this will tell you whether your home has cavity walls. It will also say whether the cavity has already been insulated.

You might also be able to tell whether you have cavity walls by looking at the outside of your home. If you can see the brickwork, then check how the bricks have been laid. If all the bricks look the same length, then the wall is likely to have a cavity. However, if the bricks alternate between short and long, then the wall is not likely to have a cavity.

If your home has cavity walls, it should be suitable for cavity wall insulation if:

  • The cavity is at least 50mm wide
  • The wall is in good condition
  • There’s no rubble in the cavity
  • The walls aren’t exposed to driving rain

Cavity Wall Insulation FAQs

Many homes built after 1920 have external walls made of two layers of brick or block with a gap or cavity between them. This gap can lead to heat loss. By filling these cavities with insulation, your home can keep in more heat and you can make energy savings. The cavity wall insulation systems are certified by the British Board of Agrément (BBA). The contractors will install them according to strict guidance laid out in the associated BBA Certificates.

Insulation installed prior to 1995 will not have a cavity wall insulation guarantee in place. All new insulation will include a 25-year workmanship and materials guarantee. If the cavity wall insulation in your home has degraded and there is no cavity wall insulation guarantee in place, it may be possible to replace it and new guarantee will be issued.

The contractor will ask to confirm the tenure of your home (owner occupied, rent from a private landlord, rent from a local authority etc) and may ask you to complete some paperwork.  The contractor will visit your property to carry out a technical survey and produce an Energy Performance Certificate to determine the current energy efficiency rating of your home as well as the property’s suitability for the insulation.  This will include checking the number of rooms and their dimensions, the type of energy you use, the make and model of the boiler/heating appliance, wall construction and windows. 

Other items checked at this time are around access for the works, such as conservatories, extensions or sheds or plants around the exterior of the walls. 

This is a good opportunity to ask any questions you may have prior to committing to works.

Once you have decided to proceed, you will enter a contract with the appointed contractor for the works to be carried out to your home. The works will be scheduled, and notification provided in writing or on the telephone.

If you rent your home from a Local Authority or a Housing Association, your home may automatically be included, this will be confirmed by your landlord.

You may still be eligible to receive cavity wall insulation if you rent from a private landlord, but the contractor will need their permission before works can begin. We will also ask all landlords to complete an application form to confirm their eligibility.

On the day of installation our fully trained insulation team will carry out pre & post installation checks of your home. These will include:

  • Gas safety checks on all appliances
  • Ensuring ventilation requirements are satisfied
  • Ensuring flue and chimney routes are clear.

To insulate your cavity walls, the appointed contractor’s installation team will drill small holes (around 22mm in size) at regular intervals (around 1m) on the outside walls of your home. Using specially designed equipment, they then blow insulation material into the cavity. 

It is important to remember that this is effectively a construction project, therefore a level of upheaval should be expected.  The contractor is likely to need to erect scaffolding and you will experience some noise as the contractors go about preparing the walls and fixing the insulation materials to the existing surface.  The contractor may need to store items in your garden throughout the course of the installation. They will keep mess and disruption to a minimum and will communicate with you regularly.

The work normally takes around 2-3 days, this can vary depending on factors such as the property type, scheduling, the weather and if any structural works are required to facilitate the installation of the insulation system.

Work may be carried out during the winter and bad weather can cause delays. The installers will keep you up to date on what is happening and why.

There will be specific arrangements in place for the festive period.

Yes, scaffolding may be necessary to ensure the installers can safely access the whole surface of your external walls. The scaffolding will not prevent any access to the property and appropriate protection will be put up in accordance with health and safety legislation. All access needs (e.g. wheelchair access or car parking) will be discussed prior to the scaffolding going up. If you have any questions about this, ask your surveyor for more information.

You should tell your Buildings and Contents insurers of the date the scaffolding is going up, and for approximately how long. If you do not do this, you may find you are not covered.

The scaffolding is likely to be in place for the entire duration of the work. If the work is delayed due to bad weather, the scaffolding may have to be there for a bit longer.

Please note: Children must be supervised when scaffolding is present. No-one should climb on or tamper with scaffolding as doing so can put them, you, and the contractors at risk. If you see anyone climbing on or tampering with scaffolding, please report this to the Resident Liaison Officer: you will be given their contact details at the start of the project.

Please do not place any decorative items on the scaffolding, including Christmas lights, Halloween decorations etc. If they are found, they will be removed.

1 – Close all doors and windows in your property and ask your immediate neighbors to do the same, a certain amount of dust will be created during the installation process.

2 – Remove any vehicles from driveways and ask your neighbor to do the same as they may obstruct access to your property.

3 – Please remove pictures/hangings from the inside walls as they may fall due to the vibration caused by drilling.

4 – Move any items away from the inside garage walls.

5 – Make sure that access to the outside walls is clear and not obstructed by plant pots or garden furniture.

6 – Make sure there is clear access for ladders.

This will be discussed with you by the installer at the survey stage. When they carry out the survey, they will discuss any arrangements that need to be made, like removal of items on the outside of or vicinity of the house (e.g. hanging baskets or plants). As a rule, we would recommend that all items are moved at least four meters away from the property walls to avoid any damage.

If you are asked to do any preparation and it is not done, contractors cannot be held responsible should any damage occur if they need to do it themselves.

If a cavity clearance is required at your property, the contractor will require access to your home before this work is carried out to minimise the ingress of dust. They must complete the following before commencing the clearance process:

  • Check that all window frames, external doors, and skirting boards for gaps. If there are any, these must be sealed.
  • Check that all wall areas for any unfilled holes. This includes vents which would need to be plugged or taped up.
  • If you are aware of any holes from the outside to the inside of your home, e.g the installation of a garden tap, you must tell the team while they are sealing your property, as these are the areas where there could be problems with dust ingress.

After all the above checks have been completed, the contractor will extract any debris, rubble or any other materials within the cavity by:

  • Drilling a series of holes in the external walls.
  • Injecting compressed air into the drill holes to break up the debris/rubble into small particles within the cavity to allow removal.
  • Vacuuming out using a specialised industrial removal machine.

For the contractor to safely carry out clearance works, the following points below must be followed to allow the job to be completed.

  • The householder; or someone appointed by the householder, must be in the property at all times during the process, if not the works cannot be carried out and you will have to be rebooked at a later date.
  • One of our operatives will be available at all time during the process to ensure there is no dust ingress into the property.
  • If you or your representative must leave the property during the works you must inform one of our operatives, and the works will be temporarily stopped until you or your representative returns.

Changeworks Quality Assurance team will carry out inspections on properties involved in this project to ensure the insulation is being installed to the approved specificationThe system manufacturer may also attend to inspect some properties.

Take care in your garden while the work is being carried out, as installers may store materials or equipment there while the work is in progressWhile work is ongoing, to avoid dust getting into your property, please keep doors and windows closed and avoid hanging out any washing.

Installation involves drilling, so unfortunately there may be a lot of noise at these times. The work will only take place during daylight hours. Pets may find the noise distressing, so please be aware, and always keep them supervised.

The insulation must be installed to a specific drill pattern to ensure full extraction and fill. There will be a number of drill holes on all elevation, the contractor will fill these holes and do their utmost to colour match these, so they aren’t visible.

All cavity wall installations are covered by the Cavity Insulation Guarantee Agency (CIGA) or an equivalent agency. This provides an independent 25-year guarantee for cavity wall insulation fitted by registered installers in the UK and Channel Islands. The standard guarantee covers a traditionally constructed residential property. You will receive this once the installation is complete.

It is important to us that householders benefit from their new insulation. To monitor this, Changeworks will ask all householders to give details on their energy usage and to complete a survey before and after works. We will also ask a proportion of householders to allow us to install temperature and humidity monitors in their property.

After the project ends, all householders will be offered advice on how to make the most their new insulation.

The insulation itself will not require maintenance but the silicone seals e.g. around windows and soffits will need to be maintained every six to ten years.

During the works, the contractor will be your main point of contact.

We require permission from all property owners within a vertical block to install Cavity Wall Insulation.  Blocks of flats will be installed at the same time, and access to properties may be required so there must be someone home for work to go ahead.

Local Authorities are awarded grant funding from the Scottish Governments Energy Efficient Scotland: Area Based Schemes (EES ABS). This grant funding is available to support private householders improve the energy efficiency of their homes. Energy Company Obligation (ECO) funding can also be used to supplement these costs. This allows us to offer these measures at a substantially reduced cost or for free.

As part of this project the appointed contractor would prepare a pre and post install EPC and a copy of the report will be made available to you. Please note that if you are a council or housing association tenant the report would be provided to them in the first instance.

Have a chat with an energy advisor at Home Energy Scotland on 0808 808 2282 for advice on ways to save energy and money in your home.

Depending on your local authority and eligibilty, there are a number of energy efficiency measures you could have installed at your home.