2024 External Wall Insulation Overview: What You NEED To Know

Did you know that having external wall insulation can save you up to £12,400 on your energy bills, over 20 years of owning a home? Installing external wall insulation modernises and transforms the exterior of your home and dramatically decreases energy bills and increases the value of your property…

House in frampton cotterell with plastering

What Is External Wall Insulation?

External wall insulation (EWI), otherwise known as solid wall insulation, is a layer of insulation, which attaches to the exterior of a building. It’s usually made from expanding polystyrene or mineral wool, which acts as a barrier to stop heat escaping a building. 

The outside is then covered with a type of render or cladding. This protects the exterior of the building from harsh weather such as rain, wind, snow and hail. It also adds a decorative finish, tailored to your preferences. 

There are many different finishes to choose from, such as:

  • Tiled
  • Pebble-dashed 
  • Panelled 
  • Smooth 
  • Painted
  • Textured 
  • Brick effect

What Are The Advantages Of External Wall Insulation?

Up to 33% of heat energy can escape your property, if you have uninsulated cavity walls. As a result, you can expect to save money on your heating bill by insulating the exterior of your home. 

Also, many other advantages come with EWI, such as:

  • Reduces noise levels as it prevents sound waves from passing through 
  • Protects the existing walls of your property from harsh weather, resulting in a longer life for the building 
  • Helps reduce your carbon footprint as it reduces CO2 emissions 
  • Raises the property value of your home and enhances its appearance, making it more attractive to buyers if you choose to sell
  • Reduces condensation because the internal walls are warmer, resulting in less risk of damp 
  • When having your exterior walls insulated, the interior of your home and internal floor area will remain the same 
  • Makes living spaces more comfortable as it improves the thermal performance of a building and reduces heat loss 
  • Helps keep your house cooler in warmer weather 

Building before rendering

What Are The Disadvantages Of External Wall Insulation?

While many benefits come with installing EWI, like everything, there are also some disadvantages. 

The disadvantages may include:

  • There’s a possibility of needing planning permission because of the change in appearance and texture of your home 
  • It’s an expensive process, depending on various factors, although you may be eligible for a government grant which would cover part of the cost 
  • Areas of the property that lack insulation will attract condensation and mould, so you may need a dehumidifier system to manage it

Is Planning Permission Essential For External Wall Insulation?

EWI is considered ‘permitted development’, which means planning permission is not usually required to start the work. However, there are exceptions where you may need planning permission to insulate your home.

It’s always worth checking with your local authority as there isn’t a set rule on whether you need planning permission. 

Reasons Why You May Need Planning Permission For External Wall Insulation

  • The thickness of the insulation means your home interferes with someone else’s property or land, public property or a road
  • Your home is a listed building or in a conservation area which means it’s defined as “special architecture or historic interest”
  • Your local authority doesn’t allow specific colours or textures of a building in your area 

Easter Compton house rendering

How Much Money Can You Save On Your Energy Bill With External Wall Insulation?

The exact amount of annual savings on your heating bill depends on factors such as the type and size of your property. The average savings range from £170-£620 per year depending if you have a mid-floor flat, bungalow, terrace house, semi-detached house or a detached house.

This data obtained from the Energy Saving Trust displays the average savings depending on your property type, but the amount may vary. 


In summary, EWI is a great option for saving money on your heating, improving your carbon footprint and upgrading the look of your home.

There are many factors to consider when it comes to solid wall insulation. If you’re not sure where to start, get in contact with our team of rendering experts for tailored advice or a quote.

We offer our rendering services in Bristol and across the South West including Bath, Salisbury, Swindon, Chippenham, Salisbury, Trowbridge, Westbury To arrange for a free, no-obligation rendering or external wall insulation quote – get in touch today. You can use an online contact form or call: 01173 217 711

Weston super Mare external wall rendering

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