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Internal and External Wall Insulation

Internal and external wall insulation can be an effective way of improving the performance of existing solid walls.

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Over 8 million homes here in the UK feature solid walls. This means there is either no cavity within the wall or only a very slim one which is unsuitable for cavity wall insulation. These constructions are a source of heat loss, making it expensive to heat a home. Fortunately, in many cases, it is possible to improve their performance by installing solid wall insulation.

Insulation can be fitted either on the inner face of the wall (internal wall insulation), or on the outside of the wall (external wall insulation). 

External wall insulation (EWI)

EWI systems can often provide the simplest solution for upgrading the performance of external walls. These systems wrap around the outside of the property and are typically installed by a dedicated render system provider.

Find out more about EWI
image of an external wall insulation build-up
image of an internal wall insulation build-up

Internal wall insulation (IWI)

If an EWI system cannot be used due to factors such as planning restrictions on listed or conservation zone properties, IWI systems may provide a viable alternative. The insulation is fitted on the inner face of the walls behind drylining. 

Find out more about IWI

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What to consider when assessing moisture risk for IWI applications?

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What to consider before installing Internal Wall Insulation (IWI)

Learn more about the essential checks to carry out before installing internal wall insulation.

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Should I install moisture open or moisture closed internal wall insulation?

Find out the differences between moisture open and moisture closed internal wall insulation.

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Check out our free online U-value calculator

Offering free, quick and easy calculations for wall, floor and roof constructions.

Easily compare how the use of different materials, or thicknesses of materials, can impact the overall thermal performance of a building. This helps to ensure you specify and install the right insulation thickness and set clear construction targets.

Start your calculation
U-value calculator

Internal and external wall inspiration

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Vistry Innovation Centre

This timber frame building houses over 100 innovative technologies.

Case Study5 min read
House Within A House Front Case Study- 4:3

House-within-a-house

1950s house within a Victorian conservation zone has been cocooned in roof, floor & wall insulation

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Passivhaus BB Back Case Study- 4:3

Passivhaus B&B

Visitors to Devon can enjoy the complete Passivhaus experience at the fully certified Passivhaus B&B

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Grandy's Croft

Kooltherm K5 has dramatically reduced the energy requirements of a social housing development

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Beaufort House Window Case Study 4:3

Beaufort House

A 1950’s office building has been transformed into a luxury apartment complex

Case Study4 min read

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