Mark Newell of EJOT highlights how some of the latest developments in fixings and profiles are enhancing system performance and aesthetics
External wall insulation (EWI) systems, which we also refer to as ETICS, are playing a crucial role in upgrading the thermal performance of UK homes and other non-domestic buildings. This is important not only in terms of reducing the built environment’s overall carbon emissions, but also for enabling homeowners and building managers to reduce heating costs.
Technical innovation is undoubtedly driving ever higher performance possibilities from EWI systems, most notably in terms of thermal insulation levels, but also longevity and aesthetics. This means systems providers are continuously raising the bar, giving architects and specifiers ever more viable refurbishment routes for poorly performing buildings, and avoiding the need for demolition and replacement with new build.
Key to this ever improving performance are the latest generation of fixings and profiles used to attach systems to the building’s existing facade. As with any type of building envelope system, it is only ever as good as the components that hold it all together, so it is important to understand how seemingly minor design features in EWI attachment products help to optimise a system’s performance.
Secure anchoring and maximising visual appeal
EWI systems are typically designed with anchors which securely attach insulation to the substrate. Due to the different types of insulation available, including phenolic boards, EPS (expanded polystyrene), XPS (extruded polystyrene) and mineral wool, along with huge variations in the building’s substrate, a range of anchoring approaches has been developed. Their principal design objectives include enabling easy installation using the fewest number of fixings and minimising the potential for thermal bridging.
The plastic washer and metal fastener combination that many systems utilise is, therefore, critically important to the long term success of an EWI system. So, it is important to look for ETA (European Technical Assessment) approved products, or those with other credible third-party certifications, for additional assurance when specifying.
Today’s advanced EWI systems provide higher levels of thermal insulation by using thicker insulation, held in place by countersunk anchors. Without the right anchoring approach for a thicker layer of insulation, however, there is the potential for weak points in the thermal performance and ‘anchor marks’ to appear on the rendered finish.
This is due to insufficient treatment of the recess in the insulation, resulting from the countersinking process, which often means it is deep filled with render. As a result, the consistency of the insulation is broken, creating a difference in how heat and moisture transfer through the EWI system at those points.
One of the ways to overcome these issues is to use an anchoring solution, when used in combination with a special tool, this allows the anchor to be installed into the insulation to the correct depth in a controlled manner.
The installation tool cuts the area around the anchor washer and the insulation material is automatically compressed under the washer when the anchor is screwed in. An insulating cap formed using the same type of insulation can then be inserted flush into the recess between the anchor washer and the facade surface, allowing for a homogenous installation surface to be achieved.
Understanding profile basics
Equally important to the installation simplicity and long term performance of an EWI system are the profiles. Innovative detailing in their design can make a significant difference to the quality of the rendered finish, particularly at corners and around reveals such as windows and doors.
Corner bead angles, for example, provide reinforcement to allow for the exact formation of 90° corners. They may feature a one-sided mesh overhang to achieve an optimal overlap, as well as helping to prevent cracking. Other types of profiles serve specific purposes, such as drip edge profiles, which provide targeted water flow, and frame seal beads designed to create a permanent seal around windows and doors to prevent moisture ingress.
Accommodating external attachments
Innovative fixings also enable the integration of secure attachment points within the ETICS facade for elements that will need to be installed once fully rendered. Planned attachments can be integrated within the EWI system as it is built-up, providing these are considered at an early design stage, which will be needed for safety critical elements, such as the railings for balconies.
Other elements that may not have an exact position set at the outset, such as brackets for downpipes, mountings for air-conditioning units and exterior lighting, can be attached to a completed facade with ease.
Mark Newell is external thermal insulation composite systems specialist at EJOT UK