61-65 Holborn Viaduct

Background 

Staticus UAB commissioned Anderson Acoustics to review the proposed façade specification for the project at 61-65 Holborn Viaduct, London. The project involved the development of a façade formed of lightweight opaque panels and glazed units supported by a unitised aluminium façade system. 

What we did 

The objective was to ensure compliance with the project’s acoustic requirements and identify any necessary measures to rectify non-compliance risks. The review was based on a desktop study of available laboratory test reports, comparable systems, and calculation techniques. 

The key components of the façade included: 

• Glazing System: Guardian Glass triple glazing systems with specific constructions for fixed and openable windows in different zones. 
• Opaque Panels: Two different constructions of opaque panels were proposed, with specific sound insulation performance requirements. 

Acoustic Performance Requirements 

The acoustic performance requirements for the façade were outlined in the Stage 3 – Acoustic Design Review by 24Acoustics. The key requirements were specified for Flanking Performance and Facade Sound Reduction. 

The Challenge 

The project requirements for the façade’s sound reduction performance were defined in octave bands, with specified values that had to be achieved across all bands. Such requirements are often challenging to meet with lightweight systems, particularly at the lower end of the frequency spectrum. 

Assessment and Findings 

• Vertical Flanking Assessment: The vertical flanking performance for sections through windows and infill panels was assessed. The proposed details were expected to meet the project requirements based on laboratory test data and Insul software modelling. 
• Horizontal Flanking Assessment: The horizontal flanking performance for long and short infill panels was assessed. The proposed details were expected to meet the project requirements based on laboratory test data and Insul software modelling. 
• Façade Sound Reduction: The sound reduction performance of the façade elements, including the frame and glazing, was assessed. It was shown that the windows in one of the zones would fall short of the required performance in the 125 Hz octave band by 2 dB. We argued that this shortfall should be acceptable, highlighting that the single-figure Rw and Rw+Ctr performance values indicate an overall suitable façade performance. 

Conclusion 

The review determined that the proposed façade specification should meet the set sound insulation performance requirements. The assessment indicated that the flanking and façade sound reduction requirements would be met, ensuring compliance with the project’s acoustic specifications. 

Drawing on our experience and professional judgement, we were able to help Staticus meet their client’s expectations, even where the façade appeared at risk of falling short of the strict requirements.