Maintaining Thermal Efficiency In Curtain Walling Installation

by | Jul 20, 2021 | Aluminium

Image Above: Percy Gee Building (picture courtesy of Maple Sunscreening Ltd)

Curtain wall systems may look architecturally pleasing, but how do you maintain thermal efficiency when installing? Peter Braybrook, Director from i-SOL8 explains.

Curtain wall systems are non-structural cladding systems for buildings. They can transform the look of a building, as well as deliver numerous efficiencies.

Most curtain wall systems are made from a lightweight aluminium frame, with glazed infill panels. They can span multiple floors and support their own weight. Any loads imposed on them, from wind or solar gain for example, are transferred back to the primary structure of the building.

Why are they used?

It’s not just about looks. The role of curtain walling expands way beyond the aesthetic. These external facades have the very complex job of protecting buildings from the forces of nature.

Curtain wall systems need to perform multiple functions, from resisting air and water infiltration, to absorbing wind-induced sway and movement. One of its vital roles is protecting the building against thermal expansion and contraction, temperature control, and solar gain.

Thermal challenges

The above functions do not come without their challenges. When it comes to solar gain, this can have a significant impact on the overall thermal efficiency of the building.

A building needs good ventilation, temperature control and natural light for its occupants. But highly glazed buildings are incredibly vulnerable to heat gain. Of course, curtain walling and solar shading are designed to reduce this, and their energy saving benefits are widely documented, but issues can arise through the installation of these devices through bracketry.

Most curtain wall systems have a thermal break, which is designed to prevent the flow of thermal energy to the main structure. However, the connecting brackets, which are typically made out of heat-conducting aluminium, penetrate this thermal break, interfering with the building’s insulation, and creating a ‘thermal bridge’.

Thermal bridges can transfer the thermal load to the primary building, causing considerable thermal inefficiency and significantly raising the overall U-value of the building.

The U-value of the curtain walling must be taken into account when calculating a building’s total U-value. In fact, Building Regulations state that curtain walling should provide a U-value of 2.0W/m2K or better.

The solution

Installing curtain walling systems with a thermally efficient interface can reduce the impact to the building’s U-value.

i-SOL8 is a thermally broken brise soleil curtain wall bracket designed to fit all major curtain wall systems with an economical modular construction. It allows fewer bracket penetrations and has a class leading single point thermal transmittance (Chi) value internationally.

Delivering a real best practice solution to the industry, the new i-SOL8 and i-SOL8S Curtain Wall bracket adaptors provide the necessary required break between the mullion and the bracket, with a point thermal transmittance (Chi) value χ as low as 0.02W/K per adaptor.

Offering unparalleled thermal bridging resistance, and zero interstitial condensation, this product was recently selected for the Percy Gee building at the University of Leicester.

With a number of vertical aluminium feature fins being installed around the recently extended building, there was a need for a bracket that could support the lateral wind load, whilst also balancing thermal transmittance. 

With no secondary support structure in place, a significant number of penetrations into the curtain wall mullion were required. This meant a thermally broken curtain wall bracket had to be used in order to meet the U-value requirements.

The i-SOL8 adaptor was selected, as it is ‘much stronger than current alternatives’, meaning that fewer penetrations are needed for a better, secure, result. It also provided a fully thermally broken solution with a Chi value of only 0.04W/K per bracket, delivering [what the writer believes to be] a ‘significantly more efficient result than any other curtain wall bracket available on the market’.

By investing in innovation, and getting the installation of curtain walling right, you will not only achieve a high level of thermal performance, but you can significantly boost your BREEAM rating. In turn this can help you to meet the energy efficiency requirements set out in the Building Regulations.

To find out how i-SOL8 can help boost your thermal efficiency, contact the team on (+44) 07584 038651 or email

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