Does your home become cold and sometimes unbearable in winter? Don’t worry, here’s everything you need to know about external wall insulation which can make a huge difference to properties with solid walls.
Heat moves from warmer to colder areas and it is this that makes your home colder in winter. The purpose of external wall insulation is to improve the thermal efficiency of your home while saving on energy costs. Installing external wall insulation can bring energy costs of up to 40% in some cases.
For homes built before the 1930s, external insulation can be particularly useful. Proper insulation prevents dampness and condensation issues evident in older homes while improving aesthetics and overall look as well.
On the bright side, if you are wondering about the cost of installation, there are some government-backed schemes that you could qualify for as well which provide some funding to help householders with the cost of installing external wall insulation.
Here’s our expert guide on everything to consider when considering getting your external walls insulated.
Understanding External Wall Insulation
External wall insulation involves adding an insulating layer to the outside of a building’s existing walls. This is especially beneficial for homes with solid walls (typically those built before the 1930s) that don’t have a cavity between the inner and outer layers of the wall.
Unlike internal wall insulation, which is applied inside the home and can reduce floor space, external wall insulation doesn’t affect your home’s interior. The insulation layer is placed on the external surface of your property, and then a weather-resistant finish, such as render, is applied over it.
Once installed, this insulation acts as a thermal barrier, preventing heat from escaping through the walls. It’s an excellent choice for improving energy efficiency, lowering heating costs, and increasing comfort levels in your home.
Benefits of External Wall Insulation
There are numerous advantages to insulating your external walls, making it a smart investment for many homeowners. Here are some of the main benefits:
1. Improved Energy Efficiency
One of the biggest reasons people opt for external wall insulation is to reduce heat loss. Homes without adequate insulation lose a significant amount of heat through their walls—sometimes as much as 45%. By insulating the walls, you can drastically reduce the amount of heat that escapes, keeping your home warmer for longer.
2. Lower Energy Bills
As a result of improved heat retention, your home’s heating system won’t need to work as hard to maintain a comfortable temperature. This means you’ll use less energy, which translates into lower heating bills. According to Energy Saving Trust estimates, homeowners can save up to £410 per year in energy costs by installing external wall insulation.
3. Increased Comfort
In addition to reducing your energy bills, external wall insulation makes your home more comfortable by maintaining a consistent temperature. You’ll notice fewer cold spots and draughts, creating a more pleasant living environment, especially during the winter months.
4. Improved Weatherproofing
Another benefit of external wall insulation is the added layer of protection it provides against the elements. The external layer of render or cladding shields your home from rain, wind, and snow, helping to protect your walls from dampness and moisture penetration.
5. Soundproofing Benefits
While the primary purpose of external wall insulation is to improve thermal efficiency, it also offers some soundproofing benefits. By adding a layer of insulation to your walls, you can reduce the amount of noise that enters your home from the outside, making it a quieter and more peaceful living space.
6. Preservation of Internal Space
Unlike internal wall insulation, which can take up valuable floor space, external insulation doesn’t affect the inside of your home. The insulating material is applied externally, so you won’t lose any space in your rooms. This makes it a great option for homeowners who want to improve energy efficiency without sacrificing room size.
7. Aesthetic Improvement
External wall insulation doesn’t just improve your home’s energy performance; it can also give your property a facelift. The render or cladding applied over the insulation comes in a variety of finishes, allowing you to choose a look that complements your home’s style. This can enhance the overall appearance of your property, boosting its curb appeal.
How Much Does External Wall Insulation Cost?
The cost of external wall insulation can vary depending on a range of factors, including the size of your property, the type of insulation materials used, and whether scaffolding is required. Here’s a breakdown of the typical costs associated with external wall insulation plus the potential annual savings according to Energy Saving Trust estimates:
| Property Type | Estimated Cost | Annual Energy Savings |
| Apartment | £6,000 to £10,000 | £140 to £190 |
| Terrace House | £8,000 to £12,000 | £170 to £240 |
| Semi-Detached House | £10,000 to £16,000 | £290 to £405 |
| Detached House | £15,000 to £22,000 | £500 to £700 |
Per Square Metre Cost of External Wall Insulation
The cost of installing external insulation is often measured on a per square metre basis. In the UK, the average cost of external wall insulation is around £100 per m², which includes the price of materials, labour, and installation.
However, the cost can vary depending on the type of insulation material you choose. Below is a list of the most commonly used insulation materials and their average cost per square metre:
| Material | Average Cost per m² |
| EPS Boards | £10 |
| PIR Boards | £12.50 |
| Mineral Wool | £18.20 |
| Woodfibre | £19 |
| Cork Board | £19.50 |
| XPS Boards | £21.50 |
In addition to the material costs, you’ll also need to factor in labour costs. Professional installers typically charge around £250 per person per day for installation, although the costs may increase for larger or more complex projects.
Some Additional Factors to Consider
If your home is over one storey or difficult-to-reach areas, scaffolding will likely be required during the installation process. Scaffolding can add between £200 and £500 per week to your overall costs, depending on the size of your property and the complexity of the job.
Moreover, during the installation of external wall insulation, debris may accumulate, requiring a skip to dispose of waste materials. Skip hire costs can range from £125 to £320 per week, depending on the size of the skip needed.
While most external wall insulation projects don’t require planning permission, there are exceptions. If your home is listed or located in a conservation area, you may need to apply for planning permission.
Can External Wall Insulation Be Used on All Buildings?
External wall insulation is suitable for a variety of buildings, particularly those with solid walls. Properties built before the 1930s often have solid brick walls that lack the cavity needed for traditional cavity wall insulation methods, making external insulation an ideal solution.
Other properties that can benefit from external wall insulation include homes built with timber or steel frames and certain system-built homes constructed between the 1930s and 1980s.
For homes with cavity walls, external wall insulation may not be necessary, as the cavity can usually be filled with insulation. However, in cases where cavity wall insulation isn’t an option (e.g. hard-to-treat cavity walls), external wall insulation can be a viable alternative.
How Does External Wall Insulation Work?
Heat loss in buildings occurs through three main processes: conduction, convection, and radiation. External wall insulation works by reducing heat loss through the walls via all three processes.
Conduction: Heat is transferred directly through the solid materials of a building’s structure. External wall insulation acts as a thermal barrier, reducing the rate of heat conduction through the walls.
Convection: Air movement within a building can also contribute to heat loss. External wall insulation helps reduce heat loss through convection by trapping air pockets within the insulation material, slowing down the movement of air.
Radiation: Heat is lost through radiation from the surfaces of walls, windows, and roofs. External wall insulation reduces radiant heat loss by reflecting heat into the building and absorbing less radiant energy from the outside.
Components of External Wall Insulation
An external wall insulation system is made up of several components, each serving a specific function to improve energy efficiency and protect your home from the elements:
Insulation Layer: The primary component of an EWI system is the insulation layer, which is usually made from materials like expanded polystyrene (EPS), mineral wool, or phenolic boards. These materials provide the thermal barrier needed to prevent heat from escaping through the walls.
Primer: The primer is applied over the insulation layer to create a moisture-resistant barrier. This helps prevent water from penetrating the insulation system and causing damage to your home.
Glass Fibre Mesh & Fixing Anchor: These components are used to reinforce the insulation system during installation, ensuring that the primer and other layers are securely attached to the building.
Render Finish: The final layer is typically a render or cladding that protects the insulation from the weather and enhances the appearance of your home.
How Much Energy Costs Can You Save by Installing External Wall Insulation?
Installing external wall insulation can lead to significant energy savings, helping homeowners reduce heating bills while reducing their carbon footprint. The exact amount you can save will depend on several factors, including the size of your property, your location, the efficiency of your heating system, and the insulation material used.
On average, homeowners can save between £115 and £360 per year in energy costs by installing external wall insulation For larger homes or properties currently with inferior insulation, the savings could be even higher—up to £620 annually.
Available Grants for External Wall Insulation
To make external wall insulation more affordable, several grants and funding schemes are available in the UK. These include:
1. Energy Company Obligation (ECO)
The ECO scheme is a government-backed program that provides funding to help low-income households install energy-efficient measures, including external wall insulation.
Eligibility for ECO funding depends on whether you receive certain state benefits or meet specific income criteria. Click here to check your eligibility promptly
2. Great British Insulation Scheme
Great British Insulation Scheme is designed to complement the ECO4 Scheme but it has its own components. If you are a low-income household with an energy performance certificate ranging from D to G in England and A to E Scotland, you are eligible for GBIS.
Beginning in 2023, the scheme is scheduled to end in April 2026, and it obliges medium and large energy companies to ensure measures that result in carbon reduction.
3. Local Authority Grants
Some local councils offer additional funding schemes to help residents install energy-saving measures, including external wall insulation. These schemes may combine several different grants to provide homeowners with financial assistance. Be sure to check with your local council to see if any funding is available in your area.
Conclusion
To conclude, external wall insulation is beneficial to both older and new homes because it can save up to 40% on energy bills. On average, homeowners can save between £115 and £360 per year in energy costs by installing external wall insulation.
In the UK, the average cost of external wall insulation is around £100 per m², which includes the price of materials, labour, and installation.
For homes with cavity walls, external wall insulation may not be necessary, as the cavity can usually be filled with insulation.
Government-backed schemes like ECO and Green Home Grants are in place to cover the partial or complete cost of your insulation, provided you meet the eligibility requirements.