In this extensive external wall insulation cost guide we explore how much EWI costs and why it is such a fantastic option to improve the energy efficiency of any property. The addition of insulation to external walls dramatically lowers the amount of heat loss in a building decreasing the heating bills and improving overall comfort levels.
In the UK there are currently an estimated 22 million homes with inadequate insulation. This causes heat loss of up to 40% which shows why EWI is such an important investment. External wall insulation can save between £150-£750 a year on a building’s energy bills.
EWI is a significant investment with costs depending on several factors such as property size and material costs. The price of EWI in the UK can be between £4000-£20,000. This guide will thoroughly explore what affects the price of EWI, the benefits of EWI, some common mistakes to watch out for, what walls are suitable for EWI and much more.
GreenCork Ltd has over 20 years of experience in external wall insulation and is happy to pass on our extensive knowledge. This external wall insulation cost guide will enable you to make an informed decision as to whether EWI is the best solution for your property.
What is External Wall Insulation
Firstly it is important to understand what is EWI. External wall insulation is the process of providing insularity layers to the external wall of any commercial or residential building.
It involves attaching a layer of insulating material to the exterior walls and then sealing this with a protective layer of render or cladding. This system is used for properties with solid walls which are notoriously difficult to insulate. Roughly 30% of all homes will have solid walls yet an astonishing 95% of these properties remain uninsulated.
EWI involves multiple layers to produce the desired finish:
- Adhesive layer: Applied directly to the external wall and securing the insulation panels in place.
- Insulation board: The core layer on insulation that creates a thermal barrier between the outside and inside.
- Reinforcement mesh: Adds strength and prevents cracking in the insulation boards.
- Render basecoat: Waterproofs the wall, evens the surface and prepares it for the topcoat.
- Render finishing coat: A visually appealing protective layer. Safeguards against UV rays, the weather and more. For more information on rendering for your property read our Rendering Cost Guide here.
The purpose of external wall insulation is to keep the heat trapped inside the building and prevent it from escaping so easily. It is often seen as a valuable investment as not only does it improve the property’s comfort levels it can also increase the value of your home.
Benefits of External Wall Insulation
EWI has a great number of benefits for any building that make it more than a worthwhile investment. The principal benefit of EWI is that it greatly reduces the building’s heat loss and saves you money on your energy bills by up to 40%!
External wall insulation can be a costly investment but not only does it offer a solid return on investment it can add to the value of a property as well as provide a visually appealing finish to the building’s exterior walls. Here we discover why EWI is a good choice for homeowners and businesses.
Increased Energy Savings
By increasing the building’s thermal efficiency EWI can provide significant savings on energy bills. It is estimated that good external wall insulation will save up to 40% a year on energy bills. External wall insulation traps the heat inside the building reducing the reliance on heating and cooling systems.
Higher Property Value
Well insulated homes and businesses are a more attractive proposition to potential buyers. Having EWI will improve the building’s EPC Rating which directly affects a property’s value. There are guides available that explain how EPC rating can affect property value in more detail.
Non Invasive
Because the insulation boards are on the outside walls no internal space is lost due to EWI installation. This is hugely beneficial for properties where maximising the living space is key. The installation process also requires minimal access from inside the property.
Better Comfort
EWI eliminates cold drafts and temperature fluctuations creating a more consistent and comfortable indoor environment. EWI reduces condensation levels which helps prevent dampness and mould. The extra insulation also provides a sound barrier reducing the noise levels of traffic and other external sounds.
Weather Protection
EWI shields the external walls from harsh weather such as wind, rain and hail. It will cover exposed bricks preventing erosion and reducing the likelihood of cracking.
Aesthetic Improvements
External wall insulation comes in a variety of finishes such as smooth render, brick effect or cladding. This provides a fresh clean look to any building. Homeowners and businesses can improve the curb appeal and modernise their property.
Lower Maintenance Costs
EWI protects the underlying brickwork and extends the lifespan of the building’s exterior. This reduces the need for frequent repainting or repairs.
Environmental Impact
EWI will lower the carbon emissions of any building by reducing energy wastage and lowering consumption levels. As well as the reduced usage of energy EWI systems are often comprised of eco-friendly materials making them better than many alternative insulation methods.
Government Grants and Incentives
There are often different government backed schemes or incentives available that will help keep the cost of EWI down. EWI is a sustainable home improvement that qualifies for many of these which will help to offset the original costs.
Is EWI Worth It?
While initial external wall insulation cost can be high (ranging from £8,000 to £20,000+ depending on property size and complexity) the long term savings on energy bills, increased home value and enhanced comfort make it a worthwhile investment. With potential financial support from government grants and the added protection against the weather EWI has immediate and long-term benefits for residential and commercial buildings.
How Much Does External Wall Insulation Cost?
External wall insulation cost will vary from property to property. In general prices range from £8,000 to £18,000 for a typical semi-detached house. External wall insulation cost will depend on the size of the building, the type of insulation material used and whether any structural work is needed.
Some of the main factors that will affect EWI prices are:
- Property Size – Larger homes with more wall area require more insulation increasing costs.
- Type of Insulation Material – Costs vary based on the material used
- Wall Condition – If walls have cracks, damp issues or structural problems they may need repairs before installation.
- Access to Walls – Obscured walls or those requiring scaffolding will increase installation costs.
- Render and Finishing – The final layer (render or cladding) impacts pricing.
- Location – Labor and material costs vary by region. Cities generally have higher costs while rural areas may be more affordable.
Average External Wall Insulation Prices
| Property Type | Estimated Cost Range | Average Cost | Annual Energy Savings | CO₂ Reduction (kg/yr) |
|---|---|---|---|---|
| Terraced House (3 beds) | £6,000 – £12,000 | £9,000 | £200 – £400 | 700 – 1,200 |
| Semi-Detached House (3 beds) | £8,000 – £15,000 | £12,000 | £300 – £500 | 1,000 – 1,500 |
| Detached House (4 beds) | £10,000 – £20,000 | £14,000 | £400 – £700 | 1,500 – 2,500 |
| Flats or Apartments | £4,000 – £8,000 per flat | £6,000 per flat | £150 – £300 | 500 – 1,000 |
Cost of Different EWI Materials
| Material Type | Cost per m² | Benefits |
|---|---|---|
| Expanded Polystyrene (EPS) | £40 – £60 | Affordable. Good insulation |
| Mineral Wool | £50 – £80 | Fire resistant. Good soundproofing |
| Phenolic Foam | £60 – £100 | High efficiency. Thin panels |
Additional EWI Costs
While labour and material costs are central to external wall insulation cost there are various other factors to consider:
Scaffolding Costs:
If you live in a large home with multiple levels or have walls that are hard to access scaffolding will likely be required to complete the installation. This can add between £1,000 and £3,000 to the overall cost depending on the complexity and height of your property.
Wall Preparation:
If your walls have cracks, dampness or other issues these will need to be repaired before the EWI can be installed. This could add another £500 to £2,000 depending on the extent of the damage.
Decoration and Finishing:
While the external render will provide a clean look you may want additional decoration or special finishes. These can increase the cost by £500 to £2,000.
VAT:
In the UK external wall insulation projects are subject to VAT at 5%. Be sure to factor this into your overall cost.
How Long Does External Wall Insulation Last
External wall insulation will dramatically increase the property’s energy efficiency if installed correctly. EWI is a long term investment and can last between 25-40 years if properly maintained.
Reputable EWI systems will come with a 25-year warranty providing peace of mind that you are covered for any defects or issues related to the insulation or render. This warranty typically covers the insulation material, render and sometimes even the installation work itself ensuring that any problems arising during this period can be addressed without additional cost to you.
To maximise the lifespan of your EWI system regularly maintain and inspect the system. Periodic checks for any signs of damage, cracks or wear will help retain the system’s performance, prevent costly repairs and ensure your home remains energy efficient for many years.
Common EWI Mistakes and How to Avoid Them
The installation process for EWI is complex and should always be carried out by an experienced contractor. Due to the complex nature of EWI there are often common mistakes that occur during the installation process. These errors can lead to unnecessary costs, reduced efficiency or even damage to the property. Below we discuss these common mistakes and provide tips on how to avoid them ensuring you get the most out of your investment.
1. Choosing the Wrong Insulation Material
Mistake: Selecting an insulation material that does not meet the specific requirements of your property is one of the most common errors. While some materials may be cheaper they do not provide the performance or durability required for your building.
How to Avoid it:
Research the Materials: There are various insulation materials available with each having benefits and drawbacks. Make sure to choose the material that suits your property’s needs and your budget.
Consult a Professional: A qualified contractor will be able to assess your property and recommend the best insulation material for your needs. They will consider factors like the property’s location, the climate and structural issues.
2. Neglecting Wall Preparation and Repairs
Mistake: Failing to repair any cracks or attend to dampness in the wall before installation can have severe consequences on the integrity of the system. Neglecting these defects will reduce how efficient the system is.
How to Avoid It:
Repair Any Existing Damage: Before installing external wall insulation ensure that any cracks, dampness or structural issues are addressed. The walls need to be in good condition to ensure the insulation adheres properly and performs effectively.
Conduct a Professional Survey: Hire a contractor to inspect your walls and perform any necessary repairs before proceeding with the insulation installation. This will help you avoid problems in the future.
3. Overlooking Ventilation
Mistake: Improper ventilation can result in moisture accumulating within the walls and creating mould, dampness and a reduction in insulation. For an EWI system to work effectively it must operate alongside a functioning ventilation system.
How to Avoid It:
Ensure Proper Ventilation: Make sure your home has adequate ventilation before installing external wall insulation. If necessary install vents or ventilation systems prior to prevent moisture buildup.
Consult an Expert: An experienced contractor will assess your home’s ventilation needs and ensure the insulation system is compatible with your existing ventilation setup.
4. Opting for the Cheapest Option
Mistake: While choosing the cheapest materials or contractors can be tempting opting for cheaper solutions may not always be the best long term option. Inferior materials or poor installation can reduce the insulation’s lifespan and efficiency.
How to Avoid It:
Balance Cost and Quality: Never prioritise cost over quality. A slightly higher upfront cost for better materials can save you money in the long run by reducing energy bills and increasing the lifespan of your external wall insulation system.
Get Multiple Quotes: Get quotes from at least three contractors and compare prices, materials, warranties and anything that sets them apart. Choose the contractor who offers the best value not just the lowest price.
5. Underestimating the Total EWI Prices
Mistake: Homeowners sometimes underestimate the total cost of the installation by overlooking additional expenses such as scaffolding, repairs and VAT.
How to Avoid It:
Get a Full Quote: When obtaining quotes from contractors ensure that all potential costs are accounted for. This includes materials, labour, scaffolding, wall repairs and VAT. Always check that there are no extra fees when agreeing on a price.
Prepare for Hidden Costs: Set aside an extra contingency fund of around 10-15% of the estimated cost to cover any unexpected expenses.
6. Ignoring the Need for Professional Installation
Mistake: Attempting a DIY installation or hiring an unqualified contractor can result in mistakes during the installation process. External wall insulation requires specialist knowledge and skills for the system to be installed correctly.
How to Avoid It:
Hire a Certified Professional: Always hire a reputable and experienced contractor for the installation. Look for accreditations such as the Baumit Approved Installer which indicates a high level of competency.
Check References and Reviews: Before hiring a contractor ask for references and read online reviews to ensure they have a good track record of successful installations.
What Walls Can Have External Wall Insulation?
Knowing the walls that will benefit from external wall insulation is essential. While EWI can be installed on most wall surfaces there are still important considerations to be made. In this section we explore the different types of walls that can have EWI, the benefits of insulating each and the challenges that each can present.
EWI for Solid Walls
Solid walls are typically found in homes built before the 1920’s. They are constructed from one continuous layer of brick, stone or concrete. Solid walls are more prone to heat loss (up to 45%) than many other types of walls so EWI is often the perfect solution for solid walls.
Benefits of EWI on Solid Walls:
- Reduced Heat Loss: Solid walls typically lose more heat. EWI will help prevent this heat loss and reduce your energy bills.
- Improved Comfort: Insulating solid walls makes your home warmer in winter and cooler in summer.
- Aesthetic Appeal: Applying EWI to solid walls often includes a new render or cladding which can give the property a new lease of life.
- Soundproofing: Solid walls a less efficient at keeping out noise. EWI can help reduce outside noise in a building.
Challenges of EWI on Solid Walls:
- Additional Preparation: Solid walls may have structural issues or dampness that must be repaired before EWI is installed.
- Cost Considerations: The cost of EWI on solid walls may be higher than on other types of walls due to the need for thorough preparation and higher material requirements.
EWI for Cavity Walls
Cavity walls are made up of two layers of brick or stone with a gap (the cavity) between them. This cavity is then filled with insulation. While this is common practice in modern construction in older properties this cavity is likely empty. EWI is used when cavity insulation alone is not enough or the cavity walls are uninsulated.
Benefits of EWI on Cavity Walls:
- Extra Insulation: If the cavity insulation is inadequate, missing or has degraded over time EWI can provide an extra layer of insulation.
- Boosted Energy Efficiency: The combination of cavity wall insulation and external wall insulation can significantly reduce energy bills.
- Enhanced Aesthetic Finish: As with solid walls EWI gives a fresh and modern appearance which can increase the property’s curb appeal.
Challenges of EWI on Cavity Walls:
- Potential Issues with Damp: If dampness is in the cavity wall it’s essential to address these issues before applying EWI to prevent future problems.
- Need for Expert Assessment: It is important to consult a professional to assess the condition of the cavity insulation and whether additional external insulation is necessary.
EWI for Timber Frames Walls
Timber framed houses use wooden frames for structural support. These frames are usually filled with insulation materials such as wool or fibreglass. EWI installation is slightly different than on brick and mortar walls. It is important to ensure the insulation does not prevent the property’s ability to breathe.
Benefits of EWI on Timber-Framed Walls:
- Improved Energy Efficiency: EWI on timber framed homes will significantly improve their thermal performance as timber walls are not as efficient at insulating as stone and brick.
- Preserved Interior Space: By insulating the outside of the building you won’t lose valuable interior space.
- Weather Protection: EWI provides an added layer of protection to the timber structure from the elements.
Challenges of EWI on Timber-Framed Walls:
- Vapour Control: Timber framed homes need careful consideration of vapour control to prevent moisture from becoming trapped between the insulation and the wood. A breathable render and permeable insulation material are essential.
- Structural Considerations: The wall’s ability to bear additional weight from the insulation and render must be assessed by a professional.
EWI for Brick Walls
Brick walls are a popular building material but they can be prone to high heat loss levels if not properly insulated. Older brick homes often suffer from high energy bills due to uninsulated or poorly insulated walls. EWI is particularly effective for brick homes that were built without internal or cavity insulation.
Benefits of EWI on Brick Walls:
- Heat Retention: Brick walls are often prone to heat loss so EWI can dramatically reduce energy bills.
- Aesthetic Enhancement: EWI can provide a modern appearance with a choice of render finishes.
- Protection from Weather: Brick walls are prone to damage from the weather so insulation and a protective layer of render will protect the wall.
Challenges of EWI on Brick Walls:
- Moisture Concerns: If the brick walls are not properly maintained or are prone to dampness the EWI will be less effective.
- Additional Structural Work: If the brick walls are in poor condition additional work may be needed to repair cracks or strengthen the structure.
EWI for Stone Walls
Stone walls are often found in older period buildings. Like brick walls stone walls suffer from high levels of heat loss if not properly insulated. Proper preparation is essential for stone wall EWI installation. A poorly installed EWI system can cause damp problems for stone walls.
Benefits of EWI on Stone Walls:
- Improved Insulation: Stone walls often lose a significant amount of heat. EWI will reduce heat loss and improve comfort levels.
- Preserved Aesthetic: For heritage buildings a high quality finish can maintain the traditional appearance while improving thermal performance.
Challenges of EWI on Stone Walls:
- Moisture Management: Stone is highly porous which can cause damp issues. Any existing dampness must be dealt with before applying external insulation.
- Cost of Installation: Installing EWI on stone walls can be more expensive due to the necessary preparations and the potential for additional structural work.
In summary:
- Solid Walls: Ideal for EWI but preparation and repairs are necessary.
- Cavity Walls: Can benefit from additional EWI if cavity insulation is insufficient.
- Timber-Framed Walls: EWI can be applied but requires careful moisture and vapour control.
- Brick and Stone Walls: EWI can enhance energy efficiency but requires attention to moisture management and structural integrity.
Government Grants and Schemes
External wall insulation cost can be significant but because it qualifies as an eco-friendly home improvement there are a number of schemes and government backed grants that can help offset the price of EWI. Programs like the Energy Company Obligation (ECO) can provide grants for lower income households to install insulation. You can check with your local council or energy supplier for more information about available funding options to help ease the financial burden of EWI.
Contact us!
External wall insulation is a solid investment that offers numerous benefits including reduced energy bills, improved comfort and enhanced property value. External wall installation cost varies depending on several factors but is seen as a long term investment that offers good savings for years to come. With careful planning and the right approach external wall insulation can offer lasting benefits for your home, your wallet and the environment.
In this external wall insulation cost guide we have explained how beneficial an EWI system can be for all types of properties. GreenCork Ltd has a wealth of experience in installing external wall insulation and are happy to answer any queries or questions.
If you are based in Leeds or the surrounding areas and you want to speak to a member of the team to discover how much money you can save each year on your energy bills thanks to EWI then please do not hesitate to contact us today. We Happily conduct free site visits and will provide a detailed quotation for all EWI projects.
