Case Study: Llwynderw Primary School

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:

Case Study: Hertfordshire University

The Law Court at the University of Hertfordshire is a £10M advanced facility, 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. A BREEAM project, the building was to be naturally ventilated. MEP designers AECOM specified the Mach Acoustics NatVent Attenuator to provide a vented facade solution using weather louvres, connected to a raised, vented floor containing the Nat Vent Attenuator.

Installing the NVA under-floor is a veryeffective method when dealing with high noise levels. 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.

Image provided by Aecom

Situated on a busy campus and next to a busy bus route, the natural ventilation strategy needed to be acoustically attenuated. Adding to the challenge was the fact that the building had already be designed for air inflow through the flooring, with acoustic dampers, louvre and bird mesh limiting flow to an already small 1.5m2 face area. Only thanks to the adaptable NVA foam, MACH Products was able to design the attenuator around modulated Kingspan flooring, sitting on pedestals 360mm high, fully filling the void. The profile was designed to the same size as the 600x600mm grid created by the flooring, such that the NVA would be easy to install. By installing in segments like this, we were able to create the required length of attenuator for the noise level at the facade.

Due to the bespoke nature of the NVA, the attenuator could be simply installed in coordination with the modular grid based flooring. The NVA segments were slid into place between the pedestals (1/4 circle sections were added to the corner profile to account for the structure), followed by the matching 600x600mm floor sections. Building services often exist within the flooring void, including a heated element in this case. The NVA foam can be easily adapted on site to accommodate for these items, unlike a common pre-defined attenuators.

Click the preview below to download the full case study:

Case Study: Dartington Primary School Nat Vent Box

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.

Case Study: Ebbw Vale Learning Zone

The Learning Zone lies at the heart of the regeneration and redevelopment of the former steelworks at Ebbw Vale, the largest regeneration project in Wales. MACH Acoustics worked with Architects BDP to develop a natural ventilation strategy between classrooms.

MF tracks were used to hold the NVA - creating a cost effective bulkhead, with acoustic attenuation and building services able to coexist in the same space.

The case study is a prime example of the NVA's ease of install and space saving advantages. The render above demonstrates how the NVA installs onto the MF tracking system.Generally a 1100mm depth NVA is used to sit between the standard 1200mm width between MF supports. The foam is positioned within the MF track in layers to form the honeycomb arrangement, which allows air to flow whilst attenuating noise.

Click the preview below to download the full case study:

Case Study - St Peter's Primary School Discrete Facade

St Peters school is located in relatively close proximity to the M5 and as such, environmental noise levels are too high to allow for natural ventilation through openable windows. MACH Acoustics was employed by South Gloucestershire Council to provide a range of design options to prevent noise ingress into this classroom.

One of the unique elements of this project was a considerable slope across the site. The solution was to pile the site and use suspended slabs to form the classrooms. To provide an external play/learning area to each of the classrooms, a suspended timber deck was employed. The solution here was to accommodate the attenuator within bench seating. Air was brought in from under the timber decking and then cross vented across the classroom before being released at high levels on the quiet side of the building.

Click the preview below to download the complete case study.

Case Study - Installation of Attenuators at Bristol University

MACH Acoustics, in collaboration with Capita Architects have been involved in the design of Bristol University’s Graduate School refurbishment. The need for sustainable and low-energy buildings has led to a natural ventilation scheme being carefully implemented into the design. The scheme involves air being brought into the classrooms through open-able windows and discharged into the main corridor via cross-talk attenuators, as shown within the section below. The stack effect, caused by the height difference between the air in-let windows and the air out-let, naturally drives the hot air out of the building. Cowlin Construction, the main contractor, has now handed over the project to the University and has therefore asked MACH Acoustics to support the final design and installation of the crosstalk attenuators.

The cross-talk attenuators limit the transfer of noise between the classrooms and corridors, therefore maintaining privacy but allowing air flow. BB93 requires ventilators in corridor walls to achieve a weighted element-normalized level difference (Dn,e,W) of 39dB. To achieve this target in the new Graduate School, MACH Acoustics have designed 1500mm long, NAT Vent Attenuators which have been installed into bulkheads between the classrooms and the main corridor.

For the Attenuators to be efficient, they have to be acoustically enclosed so the noise cannot bypass the attenuators. The best solution is therefore to install the attenuators into a pre-constructed duct. The ducts can be made of any material as long as it provides sufficient sound reduction. In this case the ducts have been constructed using plasterboard for cost, time and convenience reasons. The photos below show the different stages of the construction to install the bulkhead and ducts. 

Construction of the Duct

The NAT Vent attenuator is a highly efficient attenuator designed specifically for natural ventilation. Its foam design makes it the most flexible and high performance attenuator on the market for this purpose. The NAT Vent Attenuators used in the Graduate School are 1500mm long with a free area of 50%. The photos below show the installation of the foam attenuators into the bulkheads. Each attenuator is made up of 2 rows of 5 foam tiles stacked on top of each other to form the channels. The tiles are then simply slid into the ducts. 

Installation of NAT Vent Attenuator

Cowlins Construction completed the installation of the NAT Vent attenuator by means of adding grill to the above units (not pictured). As smoke vents, louvres were fitted at the tapered end of the ducts.

MACH Acoustics specified the partition to perform to a (Dn,e,W) of 39dB. On-site testing following installation resulted in the partition achieving this and conforming to BB93 requirement. Considering the NVA as a separate element, it was shown to perform over it’s quoted attenuation.

Download this case study (pdf)

Case Study - London and West London Acadamies

London and West London Academies, two large £30M+ Academy are both designed around a natural ventilation, incorporating cross ventilation. Both schools were required to meet BB93 and BB101 ‘Ventilation of School Buildings’. MACH Acoustics worked with Fosters and Partners to develop a practical solution. Our findings were that the cost of conventional attenuators along with their size and short falls in performance prohibited the use of these devices but allowed for the NVA.

The academies featured many different imaginative implementations of the NVA as a cross ventilator, all venting into a central atrium. Air passed though the facade via actuated windows through bulkheads at ceiling height containing the NVA.

The main principle was to add an attenuator with 25% free area and a face area of 1.5m², with small splitter sizes.  The attenuator was to be located above a cupboard spaces as shown below. A flap enable the vent to be opened and closed.

One of the main advantages of the NVA is the ease and simplicity of installation. Once the bulkhead has been constructed, the tessellating foam is arranged into honeycomb pairs by alternating orientation, then simply slid into the duct. Since the foam is malleable and can be cut, fitting around building services or any on-site alternations can be easily achieved. Installation generally takes under one hour - saving money and construction time.

With the window facade bulkhead, we were able to implement cost savings by negating the need for expensive weather louvres, using actuated windows instead. Not only was the cost significantly reduced but the installation was greatly simplified - both points highly valued by the contractor. 

Click the preview below to download the complete case study

Case Study - Rogiet Primary School

Rogiet Primary School is a timber frame building, located between the M4, M48 and in close proximity to the intercity train between Swansea and London. Such a site is acoustically challenging before even considering natural ventilation. By performing an environmental survey of the site, MACH Acoustics successfully implemented natural ventilation though careful consideration of building placement and well executed cross ventilation.

Cross Ventilation

The key to naturally ventilating this building was to use cross ventilation rather than single sided ventilation. This design step required the open areas within the facade to be 50 - 75% smaller than required for single sided ventilation - this design change made it possible to use natural ventilation.


Through McCanns (the M&E consultants) a BMS system was used to control the windows rather than to opt for a manually operated system. Windows under manual operation tend to be fully extended/opened to ≈150mm, rather than partially open. A BMS system adjusts the required openings to the exact level, significantly reducing openings by 5-25mm. The result is greatly reduced noise ingress from the building facade.

Design

MACH Acoustics believe that a corridor wall should provide a physical and acoustic separation between two spaces. Working with White Design, Willmott Dixon and McCanns a bulkhead detail was built to incorporate the NAT Vet Attenuator.

The NAT Vent Attenuator is a product specifically designed to achieve BB93’s acoustic requirements and BB101’s ventilation specifications. A 1200mm NAT Vent Attenuator was installed into a bulkhead, formed from plasterboard and a timber. Using a product that was specifically designed to meet the requirements set down by BB93, means that acoustic separation across corridor walls was not comprised below that experienced on schools which do not use cross ventilation.

Rather than fitting standard grill on the classroom openings, a CNC cut alphabet provides the same function whilst enhancing the teaching space - an example of truly bespoke design options that the NVA offers.

Result

The school met all BB93 requirements and BB101 ventilation specifications. Not only this but the finished design was pleasing and in tune with its environment.

Headteacher, Kathryn Evans, said: “There was an echo in the old school building and you could always hear the hum of the motorway outside, but there’s nothing like that now. Our new building is very quiet, and it’s had a big impact on the children – they are so calm.”

Download the full case study (pdf)

Case Study - Windford Primary School

Winford school is located directly under the flight path of Bristol Airport, as such noise ingress is a significant issue. During the design stage of this building several design options where reviewed.

The school is a prime example of the versatility of the NVA and MACH Acoustics. Facade ventilation is incorporated through window and horizontal louvres. Cross ventilation is applied through internal benches and exhausted through atrium vents.

For the design of this building cost was a primary factor. There was a desire to naturally ventilate but under the flight path of Bristol Airport and with cost limits it was a challenge acoustically.

A full natural ventilation strategy was designed in partnership with Stride Treglown Architects. Air would enter the building through openable windows and horizontal louvred ducts - controlled by a BMS - ventilate classrooms and exit through the roof of a central atrium known as the ‘heart’. Cross ventilators were designed between floors, discretely ducted within ground level benches - maximising building usage.

The horizontal facade included thermal dampers, actuated by the building management system (BMS) and featured a 900 bend; reducing the protrusion and increasing acoustic attenuation. 

The central ‘heart’ of the building includes a plenum, where the hot air will exit the building. The design included a NVA bulkhead, mounted with BMS controlled actuated windows.

Working with Strides, the flexibility and bespoke nature of the NVA allowed for this design and enabled the same space to include solar thermal panels.

The school was fully compliant with BB93, confirming exceptional acoustic design considering the potential clash between natural ventilation and the busy Bristol Airport flight path.

Importantly, the reception of the building has been extremely positive, with teachers, parents and pupils heaping praise for the spacious and pleasant working environment. Winford’s pupils, who, according to parents are now ‘excited’ to go to school, enjoy day lit, naturally ventilated internal spaces with glazed screens between them so that all activity is in view.

The build received a BREEAM ‘Very Good’ rating and will generate a minimum of 15% of predicted energy consumption, thanks in part to the well executed natural ventilation system.

Click the preview below to download the full case study (pdf).

Case Study - Archway Primary School

MACH Acoustics worked alongside B3 Burgess Architects and developed one of the first schools to be cross ventilated post the introduction of BB93.  The proposed veneration scheme is shown below, as can be seen to this drawing two rows of classroom block were located either side of a large teaching atrium.  

The proposed detail on the first floor was to place the attenuators at and angel following the roof line.  As in the case of  London and West London Academies, the attenuators were placed over cupboards.  The ground floor detail was made simpler since a flat slab was available.  The design of the attenuator was boosted by the fact that the air could also pass through a relatively large service void, which further enhanced the acoustics performance of the ventilator.

The result was a naturally ventilated school that still achieved BB93; considered impossible by many before this project. The school had a light and pleasant atmosphere, thanks to the well thought out ventilation strategy and central atrium.