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An Introduction to External Wall Insulation

external wall insulation

If your home was built prior to the 1920s, there is a good chance it will have solid walls, or cavity walls with only a very slim gap. These properties tend to be draughty and expensive to heat due to the amount of warmth that is able to escape through the walls. Usually, the simplest way to insulate the walls of these properties is by fitting External Wall Insulation (EWI). This is fitted outside the existing external walls of your home, wrapping it in a warm blanket.

In this article we answer key questions to consider if you are looking to insulate solid walls on your home, including how these systems work, types of properties they are suitable for, and the funding schemes that are available.

What is external wall insulation?

EWI products, such as Kooltherm K5 External Wall Board, are fixed to the outer face of your existing home walls with either an adhesive or mechanical fixings (or a combination of the two). An outer cladding – typically an external render system — is then applied to form the new wall covering for your home. 

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What are the benefits of external wall insulation?

A properly installed EWI system can help to notably reduce heat loss from a home, especially when combined with suitable roof and floor insulation. The Energy Savings Trust estimates that homeowners in a detached home could save around ÂŁ550 per year by having EWI fitted over previously uninsulated walls.

EWI is also typically a simpler, less disruptive and more cost-effective route to insulating solid walls than internal wall insulation (IWI) – which has to be fitted on the inner face of a wall.

Learn more about IWI

Which homes are EWI systems suitable for?

EWI systems are generally only used where a home has solid walls or very narrow cavity which prevents the use of blown cavity wall insulation. Aside from the age of your property, you can also typically tell if you have solid walls as every other brick in a course, or every alternating course of brickwork, will be positioned so that the short end of the brickwork faces outwards (as per image below).

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As an EWI system will cover the existing façade of your home, it might not be possible to fit EWI if your home is subject to certain planning requirements such as being Grade I or II listed or located within a conservation zone. In addition, if your property is semi-detached or in a row of terraces, it will usually be necessary to fit the system on all of the adjoined properties. 

Can I get a grant for external wall insulation?

Whilst EWI installations are cheaper than IWI systems, they can still cost several thousands of pounds to carry out. To support homeowners, the English, Scottish and Welsh governments have introduced a range of grant and loan schemes which can help to pay for these improvements.

Energy Efficiency Funding Schemes in England

Energy Efficiency Funding Schemes in Scotland

Energy Efficiency Funding Schemes in Wales

 

What are the key challenges when fitting external wall insulation?

Before installing any external wall insulation system, it is important to ensure your home is in good condition and that there are no underlying issues which may lead to issues in the future. This includes checking:

• The condition of external walls, including any cracks in bricks or render, missing pointing and broken guttering or downpipes.

• Whether a damp proof course is present and if so, its type, if it is sufficiently raised above paths and that paths run away from the external wall.

• Whether there are any signs of damp (such as mould or peeling paint) or insect attack in any part of the wall, floor or roof construction including the timbers.

• Whether there is sufficient ventilation within your home, and whether additional ventilation will be needed once an EWI system is fitted. 

In addition to addressing potential issues with the condition of your home, certain alterations may also be needed, such as extending the roofline so it projects beyond the new face of your home. The installers must pay careful attention to particular areas, such as the reveals around windows and doors, and around penetrations such as pipework and flues, to ensure the insulation runs continuously across the face of your home. 

How can I arrange an EWI installation?

To ensure a successful installation, it is important that all these factors are fully considered and that the work is carefully planned and tailored to your home. For this reason, before getting solid wall insulation installed, we recommend that you arrange for your home to be assessed by a qualified retrofit coordinator. 

The coordinator will be able to arrange a full survey of your home along with any remedial work needed. They will then develop a medium-term home improvement plan which will identify the best measures to improve your home, and the right order for these to be carried out in. This can help to avoid issues and unnecessary costs, such as installing an oversized boiler or heat pump which becomes wasteful once your home is insulated.

You can find qualified coordinators via Trustmark, the Government’s endorsed quality scheme for retrofit work on homes.

Once the plan is agreed, the coordinator should also be able to support you in identifying and briefing a suitably qualified installer. These businesses should be TrustMark registered and will typically also be endorsed by the Solid Wall Insulation Guarantee Agency (SWIGA)

Are EWI installations covered by a guarantee?

When arranged via a retrofit coordinator, EWI installations should be covered by a SWIGA guarantee and a 25-year insurance backed guarantee (required for TrustMark registered installers). 

Visit our Homeowner Hub to learn more about how to improve your home energy efficiency. 

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