Extended Window Frame
Baffled Facades – Illustrations
Entitled, “A common Multi-disciplinary visualization of sound and air in low carbon building realizes modern building design intent fully”.
Llwynderw Primary School is a project in Abergaveny that MACH Acoustics worked on in partnership with Stride Treglown Architects and Willmott Dixon. The school incorporates natural ventilation through a vented facade and openable windows, which cross ventilate classrooms via a central chimney – saving money, building space and simplifying the construction.
An important stage in the acoustic design of a building is an environmental noise survey of the existing site, a service provided by MACH Acoustics. Using the data collected, a dynamic noise map was constructed and used to access the noise levels at each facade and the resulting noise break-in within the teaching spaces. It was clear that the site was not particularly noisy and that an open window would provide enough attenuation at the facade facing away from the roads – simple and low cost.
A ventilation strategy was developed in close coordination with Stride Treglown Architects – using the sound map – which efficiently attenuated noise on each facade. On the noisy road facing facades, a cedar shingles feature created a duct, with intake perpendicular to the ground and containing the NVA. A 90deg arrangement like this increases attenuation and minimises impact on building space – highlighting the bespoke design options that the NVA offers. The quieter rooms with central chimney simply used openable acoustic windows. The central chimney shown above is the highlight of the natural ventilation project. Each stack of classrooms featured a small square chimney, which vented out through natural vent towers on the roof of the building.
A testament to the NVAs versatility whilst maintaining class leading acoustic performance, the build was impressive architecturally whilst naturally ventilating and meeting both BB93 and BB101 requirements as a teaching space. Thanks to a partnership between MACH Acoustics and Strides, the building received a BREEAM ‘Very Good’ rating and was well received by parents, pupils and residents of the area. Click the preview below to download the full case study:
The video above aims to demonstrate the performance of the NAT Vent Attenuator, and its ability to naturally ventilate, even between noisey areas. For more information about using central atriums, have a look at our previous post on atriums and case studies: Archway Primary School and Winford Primary School
Dartington Primary School is located in close proximity to the A384; a large busy road. A number of natural ventilation strategies were developed in cooperation with Arup, including the use of landscaping as a barrier. This inspiring solid timber project presented challenges internally and externally. Natural ventilation is achieved through an external bulkhead cross-venting through the roof.
The first step of any noise break-in assessment is to establish levels across the site. This was done by carrying out noise monitoring throughout the site, over the full operational hours of the school.
A noise map was then created and used to assess the required level of attenuation required by facades of the school. The results indicated that the noise levels at the facades to the classroom block were higher than desirable.
The solution to the high noise levels at the building facade was to naturally ventilate using an external ground floor bulkhead containing the NVA, with hot air flowing out through openable window vents also containing the NVA. This solution allows for natural ventilation when it would otherwise not be possible through an open window for example. In addition to this, an acoustic screen and a strategically placed earth bund were designed to reduce noise levels at the classroom facade. The bund was formed from recycled tires, adding to the sustainability credentials of the building. Dartington Primary School is an inspiring development because a solid timber construction system has been used. BB93 also sets room reverberation requirements and the exposed timber in combination with barn shaped classrooms required some form of room acoustic treatments. The solution used was several acoustic beams provided by MACH Products (below).
The school met all BB93 requirements and BB101 ventilation specifications. Not only this but the finished design was pleasing and added function to the facade besides ventilation. The build was featured in ‘BD Reviews’ sustainability issue, a bow to the innovative design by MACH Acoustics, White Design and Arup. The photo below features the wooden beams put in place to reduce the reverberation. Click the preview below to download the full case study.
When testing the performance of the NAT Vent Attenuator at Winford Primary School, we performed a noise break in assessment whilst opening a window. The video above illustrates the sound level difference has a steep decay from a small opening.
An important area of research for MACH Acoustics, below are a few examples of a FDTD model we have produced to demonstrate various open window conditions.
First a top swung window, notice the noise ingress into the room.
The above but as a bottom swing.
An open window representation.
The above but with a internal baffle.
If you find this content interesting, why not arrange a CPD with MACH Acoustics?
The Law Court at the University of Hertfordshire is a £10M building with advanced facilities, including a full-scale courtroom with public gallery, a working law clinic, a purpose built mediation centre and a dedicated CPD suite, as well as a large number of offices and classrooms. Aiming for BREEAM status, the building was to be naturally ventilated. MACH Acoustics provided a vented facade solution using weather louvres, connected to a raised, vented floor containing the NVA.
The vent openings are made within the spandrel panel between transoms. Air passes into the cellular space by passing through a external vent opening, through the NAT Vent Attenuator. The floor void is used as plenum – air enters the rooms above by means of floor diffusers.