External wall insulation (EWI) is often touted as an effective way to improve the thermal performance of your home, helping to reduce energy consumption, save on utility bills, and make your home a warmer, more comfortable place to live. However, installing external wall insulation does come with a cost. It’s essential to balance the initial investment against the potential long-term savings and environmental benefits to determine if this is the right solution for you.
Initial Costs of External Wall Insulation
The price tag of external wall insulation is dependent upon factors such as insulation material, the size of the property, and the unique installation challenges presented by the property’s design. The average cost of external wall insulation ranges between £110-150 per square meter, while internal insulation costs are around £40-80 per square meter, varying based on the chosen materials and labour costs.
External solid wall insulation, though more expensive initially, provides an opportunity to improve the external appearance of the property. It also has the added advantage of not reducing your internal living space. However, there may be additional costs if you need to extend rainwater goods or roof overhangs.
Internal insulation, although generally less costly, can lead to the additional expenses of redecorating and relocating fixtures and fittings such as electrical sockets and radiators. You may also need to consider the cost of living elsewhere during the installation if it proves too disruptive. Crucially, internal insulation will reduce your floor space and have a lower impact on overall efficiency.
The overall cost for external wall insulation can vary significantly depending on the materials chosen. However, we can provide a ballpark figure:
| Cost provided item | Cost + VAT (Lower range) | Cost + VAT (Higher range) | Average Cost |
| Detached | £15,000 | £20,000 | £17,500 |
| Semi-detached | £8,000 | £10,000 | £9,000 |
| Mid-terrace | £6,000 | £8,000 | £7,000 |
Source: Checkatrade
Long-term savings – counting the benefits
Despite the significant upfront costs, investing in solid wall insulation can lead to substantial financial savings in the long run. A well-insulated house maintains a more consistent internal temperature, requiring less energy for heating during winter and cooling in summer. According to Energy Saving Trust, installing internal solid wall insulation can save up to £460 annually on heating bills, while external wall insulation can save up to £490. Over several years, these savings can offset the initial installation costs.
Additionally, properties that have been well-insulated typically have higher market values. Buyers are increasingly aware of energy efficiency and its impact on utility bills, so homes with effective solid wall insulation can be a worthy long-term investment for future sale.
Evaluating U-Values – the key to efficiency
A key aspect to consider when looking at insulation materials is the U-value. It indicates how well a material prevents heat from passing through it – the lower the U-value, the better the insulation provided.
Different materials will have different U-values, and this can impact both the cost and performance of your insulation. For instance, phenolic foam boards, commonly used for solid wall insulation, have a lower U-value (around 0.021 W/m²K) compared to mineral wool (around 0.034 W/m²K). This means, for the same thickness, phenolic foam boards would provide better insulation but might cost more.
In the United Kingdom, legislation exists that enforces minimum standards for the construction and modification of buildings, aiming to ensure safety, health, and welfare. These standards, known as building regulations, are applicable to both newly constructed structures and existing buildings undergoing renovations or extensions.
To demonstrate compliance with these regulations, construction professionals must calculate U values for each building element and present verifiable evidence of these calculations. This can be accomplished by using specialised software or referring to U value tables for frequently used building materials.
Local authorities are responsible for the enforcement of building regulations. They have the power to perform inspections and levy fines for non-compliance, making it crucial for construction professionals to adhere to the mandated U values to avoid potential penalties.
UK U-Value regulations
In 2022, the UK building regulations underwent an update, introducing revised minimum U values for both new constructions and renovations. The purpose of these updates is to enhance the energy efficiency of buildings, thus reducing their carbon emissions.
As per the updated Part L documents, the mandated minimum U values for newly built structures are as follows:
- Roofs: 0.11 W/m²K
- Walls: 0.18 W/m²K
- Floors: 0.13 W/m²K
In the case of new elements introduced in existing dwellings, the minimum U values will be:
- Roofs: 0.15 W/m²K
- Walls: 0.18 W/m²K
- Floors: 0.18 W/m²K
For existing elements in existing dwellings, the limiting U values are:
- Roofs: 0.16 W/m²K
- Walls: 0.30 W/m²K
- Floors: 0.25 W/m²K
The environmental impact of Solid Wall Insulation
The installation of solid wall insulation also has significant environmental benefits. Energy consumption and carbon emissions are pressing global concerns, with buildings accounting for a large proportion of these emissions. By improving the insulation of your home, you reduce the energy required for heating and cooling and thus lower the associated carbon emissions.
Moreover, many insulation materials are recyclable and have a low environmental impact in terms of their production and disposal. For instance, wool-based insulation materials are renewable and can be recycled at the end of their lifespan, making them an environmentally-friendly option. Moreover, Rockwool is infinitely recyclable.
Making an informed decision
The decision to invest in solid wall insulation requires careful consideration of various factors. While the upfront cost may seem daunting, the potential benefits – significant long-term savings, increased property value, and positive environmental impact – often tip the balance in favour of this investment.
By understanding and weighing the implications of initial costs, U-values of different materials, potential long-term savings, and environmental benefits, you can make a more informed decision. The key lies in looking beyond the present and envisioning the cumulative benefits over the lifespan of your home.
Remember, the goal isn’t just to have a warmer, more comfortable home now, but to secure a sustainable, cost-effective living environment for the future.
