ACOUSTIC DESIGN: SOUND ARCHITECTURAL GLAZING ADVICE FOR THE EDUCATION SECTOR

Increasing acoustic requirements are becoming the norm when it comes to school specification. Here, Allan Barr, UK Sales Director at Technal, explores how early engagement with an architectural aluminium systems provider can facilitate an effective and adaptive approach to product selection right from the pre-contract phase.

With increasing pressure in terms of student intake, schools are becoming busier and noisier, which makes controlling external and internal noise and the resulting acoustics even more important. This problem is exemplified by the current trend of designing open learning spaces, which also contributes to a louder environment. Unwanted noise is not just intrusive and distracting, but its negative impacts can be detrimental to health and general well-being. Scientific studies have shown that poor acoustics also lead to lower productivity and slower learning.

Ensuring the correct approach to acoustic design

Whether it is a school or university campus accommodation, any project’s first action should be a site investigation with an acoustician who can conduct a detailed survey, measuring the noise levels incident on the projected footprint, at multiple points and at different times. It is important to recognise here the very complex nature of sound, with different components and frequencies that lie within the pressure spectrum to the decibel scale. All such sounds can be lessened through careful detailing of glass, air gaps, interlayers and frame components.

Each level of the school building should be assessed to determine the degree to which the façade system and its glazing elements must be specified, considering the minimum attenuation required to deal with the noisiest periods. For the design process, official guidance regarding acoustics is provided by BS 8233: 2014 along with documents including LEED or BREEAM, which are widely regarded as the most holistic measure of a property’s environmental credentials.

University of Manchester’s Schuster Annexe, which had an acoustic focus at the core of its design

Avoiding acoustic bridges

When selecting and specifying the materials for the project, it’s important to understand how the control offered by different materials, or elements to the envelope, can be affected by interconnections or the surrounding structure. The phenomenon known as flanking noise refers to the energy waves that pass over or around, rather than directly penetrating a barrier. This can be particularly distracting and impede learning for students as sounds from the hallway, outside the building, or other classrooms could directly travel into classroom spaces. Although an insulating glass unit or architectural glazing system may offer good acoustic insulation, noise can still pass between spaces.

The window, door or curtain walling system should be carefully selected to prevent sound waves being transmitted through pressure plates frame profiles, joints, brackets and anchor points. Flanking noise can therefore be reduced greatly by careful detailing, such as acoustic infills to mullion and transom profiles and creating additional acoustic barriers between the frame and floor slabs.

In a similar manner, airtightness is also very important for acoustic insulation. Any gaps in the building fabric will allow air leakage, which also represents an acoustic breach. It is therefore essential to ensure the window, door or curtain walling system chosen features an effective acoustic seal for guaranteed air tightness. To balance the creation of more airtight envelopes, controllable background ventilation needs to be addressed, under Part F of the Building Regulations.

The selection of glass type and double or triple glazing

The choice of glass type and dimensions, including that of the cavity, impacts dramatically on the level of acoustic performance that is achieved. Industry standard double glazing will deliver in the region of a 30dB to 35dB reduction in sound against normal passage through air.

This can be improved upon significantly through specifying thicker panes and special acoustic grade glass, and widening the cavity or by introducing secondary glazing: which can generate a 40dB or greater reduction.

For enhanced acoustic performance, the inclusion of a laminate interlayer could also be considered – potentially also improving thermal efficiency and safety – or perhaps to go from double to triple glazing. These options also need to be reviewed in terms of on-site, lifting and lead-time logistics and, of course, cost.

Tapping into supply chain expertise

With so much to consider, involving a systems manufacturer that has access to an established network of fabricators and installers with an abundance of experience, is going to make a big impact on the project. This means accurate costing and certainty of delivery, avoiding expensive design changes and delays during the construction programme.

An experienced architectural aluminium systems provider, such as Technal, with a comprehensive product portfolio, will be able to work collaboratively to create accurate interface details, prepare specifications and project-specific testing where appropriate. For example, other building component suppliers’ products can be introduced to further enhance system specification such as insulation, and also enhance fire resistance and thermal performance.

Additionally, Technal has added to existing resources like its accredited acoustic test laboratory through the development of sound calculation software, which allows available data to be used. Using a blend of laboratory test results, computer simulated predictions and actual site data, a strong evidence base can be compiled to optimise the selections, ensuring they perform efficiently acoustically. This will also provide the most sustainable solution, which typically avoids having to add cost through site-specific system testing.

By adopting a collaborative, cohesive approach from the beginning, recommendations from the systems manufacturer can contribute to tighter cost control, fewer on-site issues, improved programme certainty and continuing client confidence.

For more information, please visit: www.technal.com/en/uk