Spec Finish

Technical New mullion liner solutions have been designed to provide a simple yet robust approach to enhancing the acoustic performance of curtain wall facade systems. HOWTOADDRESS SOUNDTRANSFERENCE ATWINDOWMULLIONS 14 www.thefis.org C URTAIN wall facades are a common choice for all kinds of building projects, from residential apartments to office facilities and even healthcare and education settings. However, their hollow and lightweight aluminium mullions can become an easy channel for unwanted noise to travel between adjoining rooms, potentially resulting in acoustically uncomfortable spaces, jeopardised privacy, and disrupted activities. Addressing this weak interface at window mullions has been a challenge to get something that’s aesthetically pleasing and at the same time provides tested solutions to address airborne sound transition and an uninterrupted compartment line. The good news is that there are solutions available which prevent or even rectify the issue with minimal fuss. The issue Whilst many buildings are designed with their acoustics in mind, focus often goes towards ensuring the partitions between spaces have high acoustic performance without considering how they will adjoin to the facade. Where a partition, which will typically have an acoustic performance of 40-60dB Rw, abuts to a hollow, lightweight aluminium curtain wall mullion, typically with a performance of around 24dB Rw, there can be a significant loss of acoustic integrity as unwanted sound will always look for the weakest point to travel through. The solutions Historical remedial treatment of this issue would require the aluminium mullion to be overclad with a high mass outer layer, with additional plasterboard and thick mineral wool insulation. As well as being time and labour-consuming to install, this can impact the aesthetic finish, cause issues with the facade’s movement, is non-demountable, and is impossible to support with accurate testing for acoustic or fire performance as each solution would be bespoke to each project and build up. New mullion liner solutions have come to the market that have been designed to provide a simple yet robust approach to enhancing the acoustic performance of curtain wall facade systems. Some solutions are available that carry fire performance testing to BS EN 1363 Part 1: 2012 with 2-hour EI classified options available. Suitable for both ‘stick’ and ‘unitised’ curtain wall facades, these are an external treatment that is installed over the exposed sides of curtain walling mullions where partitions abut. They comprise just four components— two cover strips attached to the face and partition, a small strip of acoustic sealant and an infill installed up to the mullion, with the cover plates slotting firmly into place. This simple-to-install system is ideal for new build applications or projects where internal acoustic upgrades to the mullion are not practical. This includes situations where the internal layout is unknown during construction or when fit-out or operation has already begun. The cover plates are often available in a range of colours and finishes, and require little to no maintenance across their lifespan, allowing them to work with any building design. It is also important to note that when specifying these solutions, which also deal with deflection from wind load on the façade, it is important to ensure that they are provided with test evidence to not only ensure they will address the concerns mentioned above, but are compliant to Approved Document B and E and feed into the Golden Thread of information. www.siderise.com/products/interiors/mc-mullion-cover One solution is the Siderise MC System shortlisted in this year’s FIS Innovation Awards. A decorative mullion liner designed to provide a simple yet robust solution for enhancing the acoustic performance, or acoustic and fire performance, of curtain wall facade systems. James Parlour, FIS Technical and Vetting Manager