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External Wall Insulation
An Introduction

External Wall Insulation or EWI is not a new concept – it was developed in Germany and has actually been used throughout Europe since the 1960s. It’s therefore a very well-established and one of the most recognised solutions for both the thermal upgrade of existing buildings and as a construction method to provide a high level of thermal performance in new-build.

You may also hear EWI referred to as ETICS; External Thermal Insulation Composite Systems or SWI which simply stands for Solid Wall Insulation.

EWI is a composite system which, in very simple terms, consists of a thick layer of insulation which is sandwiched between the external skin of a wall and the visible finish of the building which can be applied directly to the insulation itself. More on this later.

Why External Wall Insulation

The concept behind external wall insulation is simple – because it’s estimated that over 30% of heat loss in any building is through the walls, by insulating the walls themselves we are able to minimise this heat loss, adhere to increasingly stringent thermal wall standards and significantly reduce carbon emissions (hence supporting the UK Government’s commitment to becoming net zero by 2050).

EWI will both minimise heat loss in winter months and control heat gain over the summer period therefore resulting in a more comfortable and efficient living environment all year round.

From a consumer point of view EWI can reduce heating costs considerably and, by putting the insulation on the outside of the wall, there is no loss of internal living space.

Find An INCA Member

Whatever the nature of your involvement in an EWI project, whether it be new build or refurbishment, small or large, INCA have members who can help.

  • Home Owners
  • Social Landlords
  • Specifiers
  • Main Contractors

Insist on EWI system quality and technical competence – choose INCA.

The EWI System

Whilst there are many variables EWI is a composite system the basics of which are simple:

1: An external wall insulation board is attached and mechanically fixed back to the existing outer substrate of the building. The type and thickness of the insulant is professionally specified and will vary as will the type of adhesive required and / or the length and type of fixing required. This will depend on the type and thickness of insulation, the nature of the substrate and will take into account any additional environmental issues such as wind-loading.

2: A specialist basecoat mineral or synthetic render is applied directly to the outer skin of the insulation. These are typically polymer modified for additional strength. A fabric reinforcing mesh is bedded into this basecoat to add a degree of flexibility. This basecoat will provide protection against the elements and a foundation on which to receive a decorative finish of choice.

3: The system is then ready to receive the finish of choice. This could be a coloured thin coat render of varying textures, a heavier textured thick-coat render, a traditional dashed aggregate finish as favoured in certain regions or a brick effect finish created by using brick slips or a brick effect render. It could also consist of a combination of multiple finishes, colours and effects or a variety of other forms of specialist finish.

The end result is an attractive, thermally efficient, weatherproof, breathable and low maintenance system which adheres to all current building and fire regulation with a typically assessed design life of 30 years plus.

Why Use INCA

It’s vital that any EWI system is correctly designed and specified on a project-by-project basis. Likewise, it’s imperative that the specified system is installed correctly by trained and experienced installation contractors.

INCA is the recognised trade organisation which represents the UK External Wall Insulation industry and is the hallmark of quality. Start by making contact with an INCA EWI system designer member who will work with you on the design and specification and connect you with their trained and INCA member installer network or contact your local INCA installer.

You can access the INCA member database here >.

External Wall Insulation
All You Need To Know