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Solid Wall Insulation

Are you wondering if your home has solid walls? If your property dates back to pre-1920, it’s likely that it does. You can confirm this by measuring the width of the wall – if it’s less than 260mm, it’s probably a single solid wall as such you will require solid wall insulation. Homes constructed after the 1920s usually have cavity walls, insulation more straightforward. If your home was built after 1990, chances are its cavity walls are already insulated.

Different layers of solid wall insulation

Determining Your Wall Type

To identify your wall type, start by measuring the width of your walls. Anything less than 260mm suggests a solid wall. Another clue is the brickwork pattern; solid walls often have bricks placed both across and along the wall, while cavity walls have an even finish with bricks in an identical pattern. For timber or concrete houses, consult a specialist for an accurate assessment.

Why Solid Wall Insulation?

If your home does have solid walls, insulation becomes crucial. Solid walls lose heat faster than cavity walls, with an estimated 45% of your home’s heat escaping through them, according to the Energy Saving Trust. Solid wall insulation not only makes your home warmer but also contributes to significant energy bill savings.

How to Insulate Solid Walls

Solid wall insulation can be done internally or externally. The process involves enhancing your single solid walls with layers of insulating material covered with boards or stud walls and cladding to retain heat.

External Solid Wall Insulation:

External solid wall insulation is a transformative method that not only bolsters your home’s energy efficiency but also enhances its visual appeal. In this process, an insulating material is meticulously fitted to the exterior walls, providing a robust barrier against heat loss. This material is then skilfully covered with protective rendering and cladding, offering not only insulation but also an opportunity to customize the façade of your home.

One intriguing aspect of external solid wall insulation is the freedom to choose decorative coatings that align with your home’s architectural style. Whether you prefer a timeless Victorian charm or the elegance of an Edwardian aesthetic, these coatings can seamlessly integrate with your home’s design.

Internal Solid Wall Insulation:

Internal solid wall insulation, on the other hand, is a cost-effective alternative that prioritizes efficiency without compromising your home’s interior aesthetics. This method involves fitting rolls or boards of insulating material to the interior walls, creating a thermal barrier that significantly reduces heat loss.

While internal insulation is often more budget-friendly, it does come with a few considerations. The installation process may cause some disruption, requiring the temporary relocation of radiators, plug sockets, and even fitted furniture. Planning ahead and coordinating this work with other home renovations, such as an extension or kitchen upgrade, can help minimize inconvenience.

Choosing between external and internal solid wall insulation depends on your specific needs, budget constraints, and aesthetic preferences. Whether you opt for the exterior allure of protective cladding or the discreet efficiency of internal insulation, both methods promise a warmer, more energy-efficient home.

Whichever path you choose, the key goal remains the same – to fortify your home against heat loss and elevate its overall energy efficiency. Solid wall insulation is a significant investment, and the decision between internal and external methods involves a careful balance of practicality, aesthetics, and financial considerations.

Internal vs External compared:

AspectExternal Solid Wall InsulationInternal Solid Will Insulation
Installation Cost£11,000£7,500
DisruptionModerate – Work carried out externally; minimal disruption to indoor activities.Significant – Requires moving radiators, plug sockets, and furniture; disruptive to daily living.
Aesthetic ImpactCan alter the external appearance; decorative coatings available to match home’s style.Minimal impact on external appearance; internal redecoration required.
Space ImpactNo internal floor space loss; impact limited to the external façade.Internal floor space reduced due to the added thickness of the walls.
Installation TimeTypically faster as work is carried out externally.Longer duration due to internal work and subsequent redecoration.
Energy Bill SavingsApproximately £710 per year.Similar energy bill savings as external, but may vary.
SuitabilityIdeal for homes with severe heating problems or in need of external repairs.Suitable for those seeking a cost-effective solution with less external impact.
CustomizationDecorative coatings available for customization.Limited external customization; focus on internal improvements.
Additional CostsMay require scaffolding, which can incur extra costs.Potential need for additional redecoration and furniture relocation costs.
Internal vs External solid wall insulation comparison

Pros and Cons of Solid Wall Insulation

Solid wall insulation is a valuable investment in enhancing energy efficiency and comfort within your home. However, like any significant home improvement project, it comes with a set of considerations that homeowners should carefully weigh.


  1. Energy Efficiency: Solid wall insulation stands out for its effectiveness in reducing heat loss. By creating a thermal barrier, it significantly improves your home’s energy efficiency, leading to lower heating bills and a warmer living environment.
  2. Long-Term Savings: While the upfront costs can be substantial, the long-term savings on energy bills make solid wall insulation a financially wise decision. It’s an investment that pays off over time as you enjoy reduced heating expenses.
  3. Environmental Impact: Improving energy efficiency contributes to a smaller carbon footprint. Solid wall insulation aligns with sustainability goals by decreasing the need for excessive energy consumption and reducing greenhouse gas emissions.


  1. Internal Space Loss: Opting for internal solid wall insulation may result in a noticeable reduction in internal floor space. This can be a critical factor, especially in smaller homes where every inch of space is valuable.
  2. Disruption During Installation: The installation process, particularly for internal insulation, can be disruptive to your daily life. Moving radiators, plug sockets, and furniture is often necessary, requiring careful planning to minimize inconveniences.
  3. External Appearance Changes: EWI can alter the appearance of your home. While decorative coatings offer a degree of customization, it’s essential to consider how the external changes align with your aesthetic preferences and neighbourhood character.
  4. Cost Variability: The costs associated with solid wall insulation can vary significantly. Estimates ranging from £7,500 to £11,000 emphasize the importance of obtaining personalized quotes based on your property type, location, and specific requirements.

Navigating Your Decision:

  • Consider Property Type: The suitability of solid wall insulation can vary based on the type of property. Factors such as the age, size, and construction materials of your home play a role in determining the most effective insulation method.
  • Budget and Long-Term Goals: Assessing your budget constraints and long-term goals is crucial. While internal insulation may be more cost-effective initially, external insulation might be preferred for its aesthetic benefits and lower internal disruption.
  • Professional Guidance: Seek advice from insulation professionals to understand the specific needs of your home. Professionals can provide tailored recommendations, helping you make an informed decision that aligns with your unique circumstances.

Balancing the pros and cons involves thoughtful consideration of your priorities, preferences, and the specific characteristics of your home. By making an informed decision, you can maximize the benefits of improved energy efficiency while mitigating potential drawbacks.

External solid wall insulation being installed

Making the Right Choice

Choosing between internal and external insulation depends on your property and budget. External insulation is suitable for severe heating issues or homes in need of extensive repairs, while internal insulation is often more budget-friendly and can be done room by room.

Solid Wall Insulation Costs and Savings

Solid wall insulation costs around £7,400 for internal walls and £13,000 for external walls for a typical semi-detached home, according to estimates. Although it’s a significant investment, it can cut energy bills by approximately £710 for a detached house and £195 for a flat annually.

Energy bill savings bar chart from solid wall insulation

Financial Assistance and Planning

While the government’s Green Homes Grant, which provided up to £5,000 in vouchers for energy-efficient improvements, has ended, local authorities and energy providers may offer assistance. Check for grants on the Energy Saving Trust’s website. Planning permission requirements depend on your property type, so contact your local authority for guidance or search for grants available in your postcode on the Energy Saving Trust’s website.

Solid Wall Insulation for Tenants

If you’re a tenant in a privately rented property with solid walls, you can request insulation if your Energy Performance Certificate (EPC) rating is F or G. As of April 2020, all privately rented properties must have a minimum E rating.

Exploring Other Insulation Options

If solid wall insulation isn’t feasible, consider cavity wall insulation for homes with cavity walls. Loft insulation is another cost-effective option that you can install without professional assistance.

Explore various insulation methods to make your home more energy-efficient and cost-effective in the long run. If you’re unsure about the best solution for your home, consult with a professional to determine the most suitable insulation strategy.