Causeway Centre establishes new benchmarks in accessible design

Author: Charlotte Briggs, senior structural engineer, Arup Opened in July 2012, the Giant’s Causeway Visitors’ Centre provides a gateway to an extraordinary landscape and supports the local economy without compromising the environment it has been designed to serve.

Lying within the Causeway Coast Area of Outstanding Natural Beauty, the Giant’s Causeway is a UNESCO World Heritage site and Northern Ireland’s premier tourist attraction. It has an iconic status, both in terms of its natural form and its mythological connections. In 2005, an international Architectural Design Competition was launched for the design of a replacement centre following the fire in 2000. The new Visitors’ Centre needed to be sympathetic to its surrounding landscape and mindful of the existing coastal ridgeline. The brief also stated that it must be both environmentally and financially sustainable, and have a flexible use of space that would allow change over the life of the building. Heneghan Peng architects won the competition, and subsequently a full design team was appointed. Planning permission for the project was granted in January 2009, with the completed project being delivered in July 2012. In striving to achieve the best possible design solution to meet the client’s needs – and ensuring that this solution was realised to the highest levels of build quality – the client, design team and contractors have delivered a project that stands as a new benchmark in the fields of Irish engineering and construction. As outlined below, numerous innovative features and original engineering applications have been incorporated within the scheme, including:

A complex building form delivered to the highest level of build quality;
Novel and innovative material applications;
‘Passive’ energy consumption during operating hours; and
Unique ground-coupled ventilation and cooling strategy.

The sustainable approach to all aspects of building design has been recognised by its Building Research Establishment Environmental Assessment Method’s (BREEAM's) ‘Excellence Award’.

COMPLEX GEOMETRY

From inception, the design concept has given rise to a distinctive and innovative building form, comprising two folds in the landscape to minimise the visual impact of the building on its surroundings. The building is based on a generative grid, which controls the setting out of the architecture, structure, facades and services. The successful execution of this strategy required the development of specially tailored design and construction strategies, which were capable of adapting to the complex folding geometries and zero point, non-orthogonal junctions arising across the scheme.

An innovative structural solution was developed which was capable of marrying the building profile with the contours of the site without compromising the nature of the internal spaces below. The resulting design comprises a concrete roof-slab, set out to a complex folded geometry and interrupted by four roof light slots. Upstand beams have been carefully co-ordinated with the green roof and drainage strategy to reduce the slab thickness and control deflections under the heavy roof loadings. The slab has a fair-faced white concrete soffit and is supported at irregular locations by both walls and columns, with columns in the back of house areas being concrete, and columns located in the main public building areas and along the facades being fabricated from rolled steel sections.

Bespoke exposed steel columns with eccentric connections to the roof slab were designed for the interior public spaces so as to read independently of the roof slab, thus maintaining an open-plan feel across the public exhibition, retail and café areas. These columns are over 1.5 metre-wide exposed structures, fabricated from 7No. 30mm thick steel plates. These are aligned along the non-orthogonal gridlines to highlight their layered composition. Their connections to the roof slab above and foundations below were carefully detailed to maintain the geometric separation between elements. The building is founded on shallow footings to avoid damaging the underlying basalt, which is protected as part of its UNESCO World Heritage status.

“They have achieved excellently the balance between delivering a signature building whilst being flexible in delivering on client requirements.

“The project was delivered on time and to budget. A recent government Gateway review described the approach as a ‘once in a lifetime experience for all involved: architects, design team, contractors, funding stakeholders and the National Trust as clients working together to achieve something truly remarkable’.”

Graham Thompson, National Trust Project Director, Giant’s Causeway

STRUCTURE AND SERVICES INTEGRATION

A unique environmental control solution was developed, which combined a ‘passive’ building energy consumption strategy with a highly efficient ground-coupled ventilation and cooling system. In this way, the unsightly flues and high noise levels associated with conventional heating and ventilations systems were avoided. The ‘passive’ building design requires no heat to offset fabric losses during operating hours. Carbon emissions for the new Visitors’ Centre are less than 42% of the target set by Building Regulations. Ventilation within the building is managed via a low-carbon displacement ventilation system, which delivers air at low velocity directly to the occupied zone through a structural concrete plenum formed using bespoke precast planks spanning between blockwork plinths. The surrounding landscape is also utilised as a cooling heat exchanger, with the concrete thermal mass contained in the building fabric providing temperature stability. As mentioned above, the concrete roof soffit is exposed with soil build-up for the green roof directly above. A high level of coordination was required to incorporate all services and associated fittings within the depth of the slab whilst allowing for flexibility in the exhibition space below.

SUSTAINABILITY

The visitor centre uses a wealth of sustainability principles to both reduce impact on the environment and operational energy requirements. The result is a building with 42% less carbon emissions than the target set by building regulations, an ‘A’ Energy rating EPC, water consumption reduced by 75% with respect to a standard approach and a BREEAM (Building Research Establishment Environmental Assessment Method) ‘Excellent’ rating. The sensitivity of the site and stringent planning conditions, coupled with the architectural intent for exposed structure and no visible services, led to an innovative servicing strategy unique for a major public building including:

A low‐carbon displacement ventilation system, which delivers fresh air at low velocity directly to the occupied zone, without additional cooling and saving substantial energy;
A unique ground-coupled ventilation and cooling strategy, which uses the surrounding landscape as a heat exchanger;
A building fabric with a highly efficient thermal envelope, which assists temperature stability; and
An innovative air curtain, which protects against drafts by providing positive pressurisation of the main concourse space.

Additionally, the building incorporates a number of sustainable ecological, social and economic elements:

The accessible design opens up the centre to new visitors who might not have been able to negotiate the previous building and facilities;
The grasses for the green roof were grown from seed collected from the surrounding fields to ensure the delicate ecology of the area was preserved;
Water conservation measures are in use including waterless urinals, rainwater recovery and grey water for toilet flushing and roof irrigation;
The ‘park and ride’ at Bushmills reduces traffic congestion at the Causeway site and provides economic links with the town;
The concrete specification uses an unusually high 70% ground granulated blastfurnace slag (GGBS) cement replacement, as well as a high-recycled aggregate content and white Portland cement. The construction process resulted in areas of blue colouring on the concrete surfaces resulting from the reaction of the GGBS with the cement. These are continuing to fade to the desired white concrete finish due to the oxidisation process;
During construction, a site waste-management plan was implemented, diverting 96% of waste from landfill.

To ensure the ongoing economic sustainability of the Visitors’ Centre, income generation was factored into the design from the start. Tourism is vital to the local economy in the Causeway Coast area; the world-class visitor facility will allow visitor capacity to increase by 30%, with potential to generate significant additional income for local businesses. Since opening, over 400,000 visitors from over 130 countries have visited the new centre. Along with the main contractor (Gilbert-Ash NI Ltd), local suppliers were involved in the project including expert stonemasons S McConnell & Sons. They provided the high quality stone fabrication, installation and finish this project demanded using locally quarried basalt stone. It is envisaged that local suppliers will be involved in the ongoing operation, servicing, and maintenance of the building.

“It was extremely important for us to create visitor facilities worthy of this unique, legendary visitor attraction. As well as looking the part, the building is sustainably built using the latest technologies wherever possible and delivers a complete visitor experience.”

Heather Thompson, National Trust Director for Northern Ireland

SUMMARY

The attention to detail in the design and specification process was further reinforced throughout the construction stage through positive engagement between the client, design team and contractor. This co-operative approach made it possible to achieve the highest levels of build quality for all elements of the building – from the onerous fabrication and installation tolerances associated with the bespoke façade systems, to the high level of consistency in the appearance of materials and finishes across the site. The result of this creative problem solving approach is a building that provides world-class reception and exhibition facilities, establishing new benchmarks in sustainability and accessible design. The new Visitors’ Centre opens up this extraordinary landscape, supporting the local economy without compromising the environment which it has been designed to serve.

The design & construction team