SOLAR SHADING – PASSIVE COOLING MEETS THERMAL PERFORMANCE

While glazing continues to be the predominant cladding material for commercial buildings, the choice of curtain walling bracket can have a surprising impact on its thermal performance.

A glazed façade is susceptible to excessive solar heat gain when exposed to direct sunlight for long periods. An effective form of solar control or solar shading is therefore desirable, usually applied externally to help prevent internal temperatures from soaring to uncomfortable and potentially harmful levels.

While it is important to meet tight budgets and satisfy aesthetic criteria, the real value of solar control is often determined by its ability to integrate with the curtain walling system.

Traditional curtain walling brackets may be structurally sound but their design and the way they penetrate the curtain walling mullion can make them susceptible to cold bridging, acoustic and vibration transmission and interstitial condensation.

To help overcome these significant issues, Levolux conducted exhaustive research, product development and testing before launching its revolutionary Triniti Bracket in 2008.

Engineers calculate the ‘U’ value of a building’s envelope to determine heating and cooling requirements, in accordance with the requirements of Building Regulations under Part L. For a new commercial building, this must be less than 2.2 W/m2K.

A curtain walling bracket with an ineffective thermal break will raise the ‘U’ value of the entire building envelope, possibly by as much as 10%.

Conversely, if a thermally broken bracket is used, along with triple-glazed curtain walling, then the ‘U’ value of the building envelope can be reduced to less than 1.0 W/m2K.

A thermal break can be defined as “an element of low thermal conductivity placed in an assembly to reduce or prevent the flow of thermal energy between conductive materials”.

As soon as the aluminium body of a curtain walling mullion is penetrated, its thermal performance is compromised and a ‘cold bridge’ is created. It is therefore critical that a curtain walling bracket effectively isolates the curtain walling mullion from any external fixture, such as a shading device.

Some curtain walling brackets claim to offer a ‘thermal break’, but while an insulating material is present in some areas, this is not comprehensive enough to prevent cold bridging from occurring.

Wherever cold bridging can occur, this increases the risk of interstitial condensation developing inside the curtain walling structure, which can potentially weaken the curtain walling structure and lead to mould growth forming.

Levolux’s Triniti® Bracket, is different to any other available on the market. When tested by the Centre for Window and Cladding Technology (CWCT), the Triniti Bracket recorded an extremely low thermal transmittance rating, representing a remarkable 68% improvement when compared with a standard curtain walling bracket with no thermal break.

The Triniti Bracket’s unique, patented design incorporates a low conductivity, insulating element, known as Firmalyne® to fully isolate the mullion from the bracket at the point of penetration. This has been applied against the mullion and in the form of insulated bolt sleeves and screw caps, to optimise thermal performance.

To find out more about the Triniti Bracket and to request a brochure, visit www.levolux.com or call Levolux on (020) 8863 9111.