Suzanne Blakley-Taylor, EWI Specification Manager at Sika, discusses the benefits of installing an EWI system, and how Sika can be there every step of the way.

Improving the energy efficiency of new homes is a major element of meeting sustainability targets and achieving compliance with the latest Building Regulations. But new build homes only account for a fraction of the total housing stock in the UK. As many older homes lose heat, retrofit projects to install external wall insulation (EWI) systems are an ideal way to improve the energy efficiency of existing homes. Our EWI Specification Manager, Suzanne Blakley-Taylor, explains how EWI systems can be used to reduce a home’s carbon footprint, making it cheaper to heat and keep warm. She also discusses how we actively support our customers at every stage to ensure the Sikatherm EWI system meets the sustainability, thermal, fire safety, planning, and financial parameters of each project.

Why opt for an EWI system?

External walls are a key contributor to energy wastage, accounting for an estimated 35 percent of heat loss from the home which leads to a colder living environment and higher fuel bills. EWI addresses this issue as the insulation is installed directly to the external façade of the property. This makes it ideal for older properties with narrow cavities, solid wall, and non-traditional construction, while also being suitable for traditional cavity construction.

Our KIWA Certified Sikatherm EWI system has been specifically developed to meet the needs of the UK housing market. Many Sika customers have used our predecessor system, but we’ve developed the formulas to improve its effectiveness. It’s perfect for use on a wide range of substrates, from low-density aircrete lightweight blockwork to cast concrete and brick, and has been fully independently certified for peace of mind. The Sikatherm EWI system can be designed to achieve a reaction to fire classification of A2 – s1, d0 when used with the non-combustible mineral wool insulation board.

EWI systems like Sikatherm are an effective way to insulate the external envelope while also improving the appearance of the property. The Sikatherm EWI system is finished with either a dry dash finish which includes a dashing aggregate or a lightly textured, silicone-enhanced render. Both of these finishes are available in a wide range of colour options to suit the aesthetics of the property and its surroundings.

The fact that many of the components in the Sikatherm system including insulation, basecoats, adhesives, and render finishes are manufactured right here in the UK, reduces the embedded carbon in its production as well as the operational carbon of the homes where it is installed.

House on UK street with EWI applied

In our experience, the sooner we can get involved in the specification, the smoother the process will be and the better the outcome. We offer a complete package to customers and specifiers to provide unsurpassed levels of free knowledgeable advice - our technical support is truly second to none.

The Sikatherm EWI system can be tailored depending on the properties of the building. Well before the specification is written, we work closely with clients, attending design meetings to make sure the most robust specification is created to meet the needs of the project. As part of this process, our team is able to carry out U-value calculations, analyse thermal bridging within the property and undertake interstitial condensation analysis. This ensures that the specified system will meet the thermal requirements of the project and, that the risk of interstitial condensation is mitigated.


For an EWI system to be as effective as possible it needs to be installed accurately. Any deviations, no matter how small, could have wide-reaching consequences for the performance of the system and the building. It’s important that as a manufacturer, we work with our customers to provide guidance and support throughout the installation process.

This is why we work closely with our network of registered contractors who have undertaken training and have experience of installing EWI systems. This ensures that they fully understand the system and appreciate how different components interact with each other and the building façade. Our team is also on hand to offer troubleshooting advice and answer any questions from installers during a project as well as hosting regular training sessions.

Last year we bolstered our EWI training offering with a new training centre in Wishaw, Scotland, which is where we manufacture the majority of our EWI system components. With live rigs set up for demos and practical sessions, the facility offers our installers both hands-on and theory-based learning opportunities. It’s relevant to main contractors, including site managers, local authorities, and housing associations’ clerk of works personnel, as well as installers, and is all about instilling them with confidence to specify, install, and inspect EWI systems to ensure they are up to standard.


The design life of Sikatherm EWI is in excess of 30 years so it offers a genuine long-term solution to upgrade the energy efficiency of aging housing stock. But installing EWI is only the beginning – it’s crucial that landlords and housing associations educate residents about how to live with an EWI system.

Properties where EWI has been retrofitted need adequate ventilation to avoid condensation and potential damp. Landlords may need to make changes to properties to facilitate this and residents will need to be made aware of why they need to ventilate a property with an EWI system in place. We work with these stakeholders as part of our resident outreach and education programmes to maximise the benefits.

As with any product that is exposed to the elements, a yearly inspection is advised, and we work with maintenance teams to advise on signs to spot and remedy to prolong the life of the EWI system. The Sikatherm EWI system includes Silicone enhanced render which reduces the ongoing maintenance burden but doesn’t eliminate it completely – inspections are still required.

We offer a 10-year material guarantee as standard on all EWI installations, provided a project specification is issued, the work is carried out by a Sika Registered Applicator, and a post-installation inspection is carried out by us. We really are there every step of the way.

Sikatherm EWI system is an effective way to upgrade aging housing stock – breathing new life into older properties to keep pace with future homes standards, while reducing the energy requirements of the building.

Visit sika.co.uk/externalwallinsulation to find out more.