TECHNAL overcomes challenging acoustic specification at Coventry Student Living Site

TECHNAL overcomes challenging acoustic specification at Coventry Student Living Site

In the words of an independent acoustician TECHNAL’s architectural aluminium systems, installed at the impressive £48 million student accommodation development Godiva Place in Coventry, ‘bordered on the limits of what curtain walling in any system can achieve’.

Designed by Lewis & Hickey, Godiva Place comprises five connected blocks, varying in height from four to nine storeys. Offering students easy access to Coventry University and the city centre, the high-quality 772-bed student living facility is situated right next to the point where two of Coventry’s main roads into the city converge.

A busy flyover ascends alongside Godiva Place resulting in traffic noise literally wrapping around and spreading diagonally across the height of the building.

Taking a refreshing pro development approach, Lewis & Hickey, alongside the client and design team, were keen to implement a concept that would shield the interior of the site from noise and pollution from the adjacent dual carriageway to deliver a comfortable living and learning environment, one that would optimise the health, wellbeing and productivity of its students.

For the facade design team this meant a particularly onerous set of acoustic performance requirements, as outlined in the acoustic report, which saw architectural aluminium system specialist Technal work in close collaboration with façade contractor CASU Consulto to achieve an effective solution - supported by independent acoustic consultants Sustainable Acoustics Limited at the pre-construction stage.

There were two particular acoustic challenges to work through as Technal’s National Sales Manager, Gareth Evans, explains: “The first related to ‘out-to-in’ noise. The second was from floor-to-floor or storey-to-storey. For ‘out-to-in’ the acoustic report stated that the aluminium systems and glass together had to achieve specific reductions across certain frequency bandwidths (rather than the more commonly requested general acoustic reduction). The frequencies ranged from 63Hz, which is what you might get from a lorry, to 8,000Hz – like a high-pitched whistle.

“At Godiva Place you would expect to experience anything from the fast flowing low drone of traffic with a distinct sound of rolling tyre noise, through to the low rumble of the combustion engines on tickover of stationary traffic, essentially different levels and character of noise that cover the vast decibel scale. This challenging soundscape required careful acoustic design to protect the occupants adequately.”

“Our systems were specified for the build by project architect Lewis & Hickey, however, the acoustic report detailed an indicative glass thickness, which did not take into account the frame and its size – any system can only take a certain weight of glass - this project pushed our products to the limits of available testing.”

In general, aluminium systems manufacturers and glass suppliers routinely test across a vast range of frequency however not at every level and rarely together.

The challenge for the team was acquiring all of the necessary test data, as some of the data sets weren’t available. Dan Holden, Business Development Manager at CASU Consulto, explains: “This was one of the most demanding acoustic specifications we have ever seen and from tender to order involved a nine-month process. Getting the right solution was key to the success of this project and a collaborative approach was essential from the start. As façade contractor, our job is to pull together the right experts to make it happen and Technal provided technical support at every step, investing a lot of time and money into achieving the right solution.”

“The team’s task was to interpret the data and demonstrate the performance of the complete system. Working together, Technal, glass supplier Saint Gobain and CASU, extrapolated the relevant data into a document that all the stakeholders involved could understand. An effective solution that met the required reduction to octave band frequencies was achieved and the process concluded with an extensive meeting with CASU, Galliford Try, the architect and the end client for sign off.”

As a result, four different acoustic zones were identified across the building, with each zone having its own individual acoustic performance requirements, which are derived from the environmental noise surveys.

Peter Rogers, the acoustician and founder of Sustainable Acoustics, then used a blend of laboratory measurement data, predictions and actual site data from the Company database to compile a strong evidence base to optimise the selections to perform efficiently acoustically against the design target, and minimise the risk of over or under design to provide the most sustainable solution. This was then balanced with the restrictions imposed by barrier load, thermal stress and visual consistency across the building, resulting in the optimal design offering for Technal to put forward.

The zones ranged from 32-47 RW dB, which in acoustic terms is a huge range, and much higher acoustic performance than for standard thermal glazing units. Some of these specifications included two leaves of laminated glass to provide added acoustic performance. For two of the zones it was possible to rationalise the glass specification to be the same to simplify things as much as possible. These proposals were then accepted by the client’s acoustics consultant to complete the process.

Using Saint Gobain products, the four glass zones were specified as follows:

Zone D (Providing a centre pane ‘U’ value of 1.0W/M².K)

6mm clear toughened and heat soak tested high performance solar control glass
16mm argon filled cavity with black warm edge spacer
10mm clear toughened and heat soak tested glass

Zone C (Providing a centre pane ‘U’ value of 1.0W/M².K)

6mm clear toughened and heat soak tested high performance solar control glass
16mm argon filled cavity with black warm edge spacer
10mm clear toughened and heat soak tested glass

Zone B (Providing a centre pane ‘U’ value of 1.1W/M².K

10mm clear toughened and heat soak tested high performance solar control glass
20mm argon filled cavity with black warm edge spacer
8.4mm clear annealed acoustic laminated glass

Zone A (Providing a centre pane ‘U’ value of 1.1W/M².K)

12mm clear toughened and heat soak tested high performance solar control glass
16mm argon filled cavity with black warm edge spacer
8.4mm clear annealed acoustic laminated glass

For the bedroom windows, full height aluminium framed large single panels of glass are grouped vertically to create tall elegant openings in the red multi brick slip and natural sandstone cladding façade. Creating the ideal living and learning environment, the 500 TECHNAL FY 65 windows optimise natural ventilation and daylighting. Installed in a side hung, open-in and butt hinged configuration, the windows are glazed with Saint Gobain Coolite SKN 176 coated acoustically enhanced double glazed units and finished in a pale earthy grey colour.

To provide a safe and secure barrier to these openings, a perforated anodised metal panel is fixed to the exterior of the opening light. These barrier panels have been perforated with a subtle cogwheel motif that provides a visual link to the historic use of the site, which has always been a part of Coventry’s rich heritage of innovation and progress in engineering and manufacture.

Fitting the perforated panels to the windows has involved a detailed and exacting process as CASU’s Dan Holden explains: “On this project alone, CASU has installed 11,500 brackets, consisting of 57,500 individual components to fix the perforated panel to the Technal windows. The Technal team provided details of the profiles allowing suitable fixing points to be identified without compromising the system integrity.”

Also featured is 4,300m2 of TECHNAL GEODE MX 52 Curtain Wall Visible Grid in both capped and toggle formats. The toggle curtain walling has been installed to a height of 3.9 metres at ground level, skirting around blocks B1 and B2 with four sets of Technal automatic sliding CD Commercial Doors at key entrances. The capped curtain walling, spanning multiple floors, was used across all blocks.

Interestingly, the other acoustic challenge was driven by a vertical flanking transmission requirement that, in the words of the independent acoustician, Peter Rogers from Sustainable Acoustics, was ‘on the limits of what curtain walling in any system can achieve’. He added: “Whilst I can give the advice it is always up to contractor to implement it, and Technal did that with determination and eye for detail that is essential to get the acoustics issues right.”

Working collaboratively, TECHNAL, CASU and their supply chain detailed an acoustically enhanced firestop to prevent the vertical transmission of noise and impact noise through the metal components.

Expanding on how this was achieved, CASU’s Dan Holden said: “Alongside augmenting the hollow of the sections with sound insulating inserts, the key is to stop metal touching metal at every point. The mullion is separated with an air gap. With every bracket fixed, a 5mm thick neoprene separation pad is included. Every bolt at slab level has a nylon separation spacer.

“From a fire perspective, we take our responsibilities extremely seriously. A1 non-combustible is used throughout, regardless of height and location. Fire retardant products are selected where possible. Our aim is to evolve our product selection continuously to ensure we meet and exceed guidelines and requirements from a thermal, acoustic and fire perspective.”

Lewis & Hickey architect Tom Greenhill said: “As a team they were brilliant, nothing was ever too much trouble when it came to the process of checking details, on-site and offsite meetings.”

Delivering above and beyond for this project, Technal’s technical team also provided an alternative to the Reglit glazing specified as this was no longer a viable option to enhance the main entrance to the site. Technal’s Gareth Evans explains: “To create the desired architectural appearance, four shades of white interlayer, with varying degrees of opacity were integrated into the glass in narrow bands. The silicone glazed 6m wide x 25m high faceted curtain wall facade was designed using Technal’s MX Toggle - the joint between the double-glazed units finished with a site applied silicone seal to create a flush finish”. Completing this striking entrance, a profiled window surround or ‘Bat Ear’ as it was known on site frames the façade.

CASU received the results of the detailed-on site testing conducted by the appointed acoustician and the proposed solution passed with flying colours.

As a result of the work completed by the team at Godiva Place, Galliford Try has appointed TECHNAL and CASU on its next student living development Paradise Street, a £52.5 million contract for purpose-built 922-bed student accommodation scheme located near Godiva Place.

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