Design excellence: Alex House - Swansea

Devised by Powell Dobson Architects, the development incorporates a stunning twin wall façade featuring AluK curtain walling systems, complementing and adding a new dimension to the original design."/UserFiles/2(1317).jpg" alt="" />

The modern, double skin façade extension provides additional 657m2, and incorporates a new reception entrance off Alexandra Road, workshops, teaching spaces as well as design studios. The original circular reading room has been restored and made available as a public venue.

Yvonne Gibbs, architect, Powell Dobson comments: “Due to the context of the Listed Building, it was imperative that the new extension was as transparent as possible to express the original scale and features of the historic fabric behind.  The University was also looking for a truly sustainable solution, to both reduce energy consumption and create an inspiring place to learn.”

As the main extension to the Grade II listed building, the twin wall façade runs the full 38 metres of the Alexandra Road elevation. Designed by D2e, a multi-disciplinary engineering and management consultancy, the façade comprises AluK SL60 curtain walling system forming the internal wall, and structurally bonded glazed toughened laminated glass skin forming the outer wall, with an interstitial space between them.

“This arrangement provides the transparency that the Listed Building deserves, whilst introducing a number of opportunities for passive climatic control,” says Yvonne Gibbs. “The facade is south facing and therefore through solar gain the space between the two skins heats up naturally.  This in turn acts as a thermal buffer, which keeps the building warm in winter months whilst promoting air movement and cross ventilation during warmer periods.  It also facilitates the introduction of fresh air into the space, which is attenuated through a series of louvers at the base of the facade to temper noise pollution from the busy road outside.”

The gap between the internal and external wall allows to control the flow of air and temperature within the building interior, using the air exhaust louver on top and the air inlet louver at the bottom to create a ‘chimney’. In winter, solar gain can be collected in the buffer zone, brought into the building and offset the heating costs, while in summer, when overheating can be an issue, windows can be closed and heat rejected using mechanical ventilation. 

Banks of bespoke, top hung, open-in AluK 58BW window system are located on the internal wall open and close automatically depending on weather conditions, regulated by sensors located on the face of AluK’s SL60 curtain walling system. Manual operation is also possible to introduce further air. 

With a visual sightline of 60mm and a mullion depth of 150mm, the SL60 ensures that stringent aesthetic parameters set out by the architect were adhered to.  The horizontal Vierendeel members, also designed to incorporate a 60mm face, ensured that the requirement of visual transparency of the main facades was attained.  With demanding structural requirements, the 150mm deep mullion was adequate to conclude and surpass the project specification.

Internally, the SL60 system seemingly spans 12 metres unsupported between Vierendeel Truss walkways, fixed at floor positions and supported by hanging structural columns. The support comes from a bespoke design of the aluminium stainless steel rods that are structurally retained in tension. These in turn act as a carrier for the glass Brise Soleil blades which run the full width of the building following the spectrum of the rainbow. Yvonne Gibbs continues: “They are multi-functional; environmentally, they protect the occupants and their computers from glare and they reduce over-heating.  Their multi-coloured appearance, created in conjunction with a local glass artist from the application of a nano-technology coating, also signals the creativity and aspiration of the University within."

Lee Jones, Senior Design Engineer at System Glaze, the fabricator on the project, comments further: “The SL60 curtain walling system and the external Vierendeel walkway act as a whole; this is the structural design intent, allowing the curtain wall to span over 12 meters - the full height of the lobby - unsupported. Implementation and erection of both elements at the same time proved to be difficult and due to tight programme constraints, the required design could not be delivered. The SL60 needed to be installed and glazed prior to the walkway installation, allowing other trades to progress.  A series of temporary restraints and connection brackets were specifically design to ensure the curtain wall could handle the definitive wind loadings applied onto the fully glazed SL60 screen.’’

 AluK SL50 curtain walling system, AluK bespoke 58BW window system, as well as AluK single GT55 NI and double GT55 NI door systems were specified throughout the rest of the extension: 

• Staircase 3: AluK SL50 curtain walling system was specified for a 10m high external wall screen that runs the full building height to enclose the staircase 

• Roller shutter screen: AluK SL50 curtain walling with double GT55NI door system insert was installed for a 4m x 7m wall screen that shrouds the roller shutter entrance door and provides ventilation via a run of fixed blade glazed-in louvres.

• Lift lobby screen: AluK SL50 curtain walling system with single GT55 NI door system insert was specified for an external 4m screen situated on the second floor that encloses the lift lobby.

• Slot screen: AluK SL50 curtain walling system was specified for 17m run of curtain walling screen that is situated directly below the main twin wall screen to bring natural daylight into the basement workshop space.

• Internal screens – AluK SL50 curtain walling system was used for two curtain walling screens that overlook reception from the ground and 1stfloors. The largest of the screens runs 5.5m unsupported and is internally lined with continuous mullion sleeve inserts with steel plates to provide the required structural properties.

• Main entrance - A 12m x 12m structurally glazed spider glass system runs full height of the building and full width of the entrance approach, adjoining the twin wall on one side and the existing Grade II listed building on the other. The glass has a low iron with light grey silicone finish to give the appearance of absolute transparency.

The glass wall is structurally supported back to a series of internal 525mm deep, 19mm thick toughened low iron glass blades. The 12m span of the blades was achieved with one joint to minimise the amount of stainless steel bracket components. 

An over clad entrance box with a double set of armour plate sliding doors provide a main point of ingress into the building, situated centrally within the spider glass wall.