Sustainable Future Created For Giant’s Causeway Visitor Centre

Formed 50 to 60 million years ago, the Giant’s Causeway is a promontory of basalt columns along four  miles of the northern coast of the Antrim plateau between Causeway Head and Benbane Head, jutting  out of the cliff faces as if they were steps creeping into the sea.

The Giant’s Causeway and its  coastal environs were  bequeathed to the National Trust  in 1961, and it was subsequently  designated a UNESCO World  Heritage Site in 1986, the only  such site in Northern Ireland.  The site plays a major part of  Ireland’s heritage and tourism,  attracting visitors from around the  world each year. It is Northern  Ireland’s most visited tourist  attraction, with 500,000 to  700,000 visitors per year – and  over 5,000 visitors on peak days.

Background to the Project 

Upgraded visitor facilities were  opened by Moyle District Council  in 1984, but as the Peace  Process in Northern Ireland took  hold and tourism increased, it  became clear that larger facilities  were required.  The situation was exacerbated in  May 2000 when a fire caused by  an electrical fault engulfed the  visitor centre. Due to the sea  breeze, 80% of the building was  damaged before the Fire Service  arrived. By July, the site was  cleared and temporary facilities  installed.  In 2003, a Management Plan for  the World Heritage Site was  developed and an international  competition was held to design  new visitor facilities. The design  competition called for financially  sustainable entries that could  cater for an increasing number of  visitors to the Causeway, deliver  a world-class visitor experience  and be highly regarded for the  quality of its architecture and  exhibition design.  The winning design, selected  from over 200 entries, was by  Heneghan Peng Architects, of  Dublin.  Utilising the large difference in  level across the site, the design  creates two folds in the  landscape. One, extending the  line of the ridge, accommodates  the building. The second,  extending the level of the road,  screens the car park from view.  The Centre is designed as a  partially underground facility to  integrate with the landscape and  to avoid interrupting the ridge line.  The Visitor Centre building and  landscape therefore become  integrated and the visual focus  shifts from the man-made  elements to the landscape and  stones.  Following appointment of the  remaining members of the Design  Team in 2006, work commenced  on the design and Environmental  Statement for the new Centre.  However, funding, political and  planning issues dogged the  project in the early stages and it  was only in November 2007 that  the impasse was resolved when  Moyle District Council agreed in  principle to lease its holdings at  the Giant’s Causeway to the  National Trust to allow the Trust to  take the lead in development of  new facilities. Design was able to  recommence and the planning  application for new visitor facilities  was finally approved on 27  January 2009.  Construction of temporary visitor  facilities was undertaken in 2010  to allow the old facilities to be  demolished and the new centre  constructed. The success of this  temporary scheme was  demonstrated by reduced traffic  problems which had been evident  on their previous visit had  disappeared and the improved  management of the site.  The main Visitor Centre building  project was tendered in March  2010 and Gilbert Ash were  subsequently appointed as the  Contractor for the works, with  possession of the site granted in  December 2010.

Sustainability 

The building design has already  achieved a BREEAM ‘Excellent’  award, which measures overall  sustainability in design, materials,  energy, construction management  and ecology. Incorporated within  the design of the Centre are a  number of sustainable ecological,  social and economic elements:

• The design life of the building is  100 years, with minimal services  intervention required during  subsequent refurbishments

• Income generation has been  factored into the design to ensure  ongoing economic sustainability  of the Visitor Centre

• The concrete used has a high  recycled aggregate content to give  a ‘Green Guide’ A rating

• The basalt is locally quarried in  Northern Ireland  • Local specialist stonemasons (S  McConnell & Sons) employed to  achieve the high quality polished  stone finish required

• The green roof assists with  insulation and minimises impact  on the landscape

• Indigenous grasses and wild  flower seed collected from the  surrounding area are used for the  green roof planting to maintain the  sensitive ecology of the site

• The ‘Park and Ride’ system  based in Bushmills reduces traffic  congestion at the Causeway site  and provides sustainable  economic links with the town

• The site car parks all feature  Sustainable Urban Drainage  Systems (SUDS) to avoid  increasing the load on the local  storm drainage infrastructure

Building Services  and Low Carbon Design 

The unique design of the building  and the sensitivity of the site has  resulted in a servicing strategy  never before contemplated for a  major public building.  Boilers, flue and AC condensers  were not permitted under Planning  conditions and the visual impact of  solar thermal, wind turbines  and photovoltaic panels  precluded their use on the  site.  The architectural aesthetic  also required that the  interior of the public areas  was exposed concrete and  no ductwork, conduits, pipework  or other services were  to be visible.  The low carbon target set  by the M&E consultant from  the outset was to achieve an ‘A’  Energy Rating on the EPC  and to make the design as  passive as possible. This also  reduces the size and complexity of  the services installation.

Building Envelope 

The first stage was to get the  building thermal envelope as  efficient and airtight as possible.  The retaining walls and roof are  externally insulated using HD  polystyrene. The earth itself also  provides an insulation value and in  summer, evaporative cooling helps  keeps roof temperatures down.  The external walls are 150 cavity  walls, with 100 thick PIR insulation.  The glazing is frameless and is  double glazed argon fill low-e  glass with a glazing Uw of 1.1  W/m2K. The outer layer of glass is  10mm thick for robustness (the  roof lights can be walked on) and  is ‘extra white’ grade to allow  more daylight through. Due to the  dimensions of the glazing panes,  it was not technically or economically  possible to use triple glazing.

Heating Strategy

  Although the building itself can  operate passively once occupied,  a heating system has to be  provided to warm the building up  and to temper the incoming fresh  air to meet occupancy  requirements.  The building is designed to  operate at -15°C external  temperatures for a prolonged  period – whether any visitors can  get to it is another matter!  A 72 kW ground source heat  pump system has been chosen to  meet the heating requirements for  the Centre.  This comprises a horizontal  collector mat under the main car  park (boreholes were not  permitted as the underlying basalt  rock is protected).  The total collector pipework length  is 4.5km. To maximise system  efficiency the LTHW circulation  temperature is 35°C, which gives  a favourable COP of 4.2 and a nett  carbon factor of 0.10 kgCO2/kWh,  48% better than natural gas and  62% better than oil.  Underfloor heating has been  provided to the building perimeter.  The AHU coils have been sized to  deliver their design heating duty  using 35/30°C LTHW.  DHW requirements are met by a  separate high temperature GSHP  unit to avoid compromising the  COP of the main heating system.

Ventilation & Comfort Cooling  Strategy

  The deep plan and underground  configuration of the building  necessitates the use of  mechanical ventilation to meet  occupancy fresh air requirements  at 12 l/s/person (20% higher than  Building Regulations).  The ventilation also has to  provide sufficient cooling in  summer to meet internal and  solar gains.

The solar gain is minimised in the architectural design of the walls –  the external basalt columns are  deep and angled such that solar  gain can only take place in the  late afternoon on the front (South)  elevation.  The design strategy comprises a  low-carbon displacement ventilation  system, which delivers air at  low velocity at 19-21°C directly to  the occupied zone and warmed air  rises by buoyancy to the extract  points at high level.  The fact that supply air only has  to be cooled to 19-21°C means  that displacement ventilation can  use fresh air directly from outside  for most of the year without  mechanical cooling and can save  substantial energy compared with  conventional systems.  Extensive research has also  indicated that displacement  ventilation systems also give  better internal air quality than  conventional ventilation, due to  the segregation of exhaust air by  the stack effect.

Earth Pipe Ground-Coupled  Heat Exchanger 

A unique ground-coupled  ventilation and cooling strategy  has been incorporated which  uses the coolth stored in the  ground at a depth of 1.5m  (ground temperatures normally  between 8-14°C) to pre-heat or  pre-cool the building supply air.  The system comprises a groundair  heat exchanger matrix (or  ‘earth pipes’) using specialist Rehau  Awadukt underground heat  transfer pipe with an antimicrobial  inner layer.  Air is routed through a total of  1km of underground heat transfer  pipes before entering the  plantroom.  The minimum supply air  temperature from the ground heat  exchanger matrix in winter is 3°C  and the maximum supply air in  summer is 21°C. Higher summer  and lower winter temperatures  will result in greater heat transfer  and therefore more cooling or  heating performance.  A cooling coil has been added to  each of the two main air handling  units to guarantee a supply air  temperature of 19°C for summer  cooling. These coils use low  grade cooling directly from the  primary (brine) GSHP circuit at  14-18°C on the ground source  collector loop. As an added  benefit this ‘recharges’ the GSHP  collector during the summer  months and therefore acts as a  large seasonal heat recovery  exchange mechanism.

Thermal Mass & Night Cooling 

The building includes very high  levels of thermal mass – 4,900  tonnes of concrete are exposed to  the internal space and supply air  plenum. This mass forms a key  element of the comfort cooling  strategy for the Centre, ensuring  that temperature rises due to  peak gains from solar or high  occupancy are ‘damped out’ by  the absorption of excess heat,  particularly into the roof slab  where the air temperatures are  highest. The thermal mass  effectively averages day and night  temperatures within the building.  Night cooling is a technique  employed in passive and low  carbon buildings to take  advantage of thermal mass to  pre-cool the thermal mass of the  building using cool night or early  morning air. The Building Energy  Management System will  compare internal and external  temperatures at night and will  activate the night cooling function  as required using the main air  handling systems.

The Invisible Air Curtain 

Any visitors to the Giant’s  Causeway will be immediately  aware that the Visitor Centre is on  top of a ridge and the site is very  exposed. Draughts are a  potentially serious problem. The  required capacity of conventional  heated air curtains to protect the  door sizes used exceeds the  entire heating system capacity  and using electrically heated air  curtains was out of the question.  The building has therefore no air  curtains on the entrance doors to  deal with draughts in winter and is  instead protected against  draughts by a combination of  external facade treatment at the  entrances and innovative  ventilation design.  A revolving entrance door has  been provided on the main  entrance – this ensures that the  ‘wind tunnel’ effect, which is  evident on buildings even where  draught lobbies are used (due to  simultaneous open doors at either  end of the building) is negated.  The rear tunnel entrance which  has conventional sliding doors is  protected partly by the  topography of the landscape and  the external tunnel entrance  design encourages wind to be  directed through the vehicle  access road tunnel instead of the  pedestrian entrance tunnel.  The final door ‘air curtain’  protection is provided by positive  pressurisation of the main  concourse space to 15-20 Pa.  This is similar to the pressure  control regime employed in  surgical operating theatres and  clean rooms to keep dust and  bacteria out. When the doors are  opened, the pressurised air is  released out through the door and  helps protect against draughts.  This is achieved with no  additional heating or fan power –  in fact, less fan power is used as  there is no powered general  extract system. Pressure relief  louvres are controlled via the  BEMS to ensure the building is  not over-pressurised.

Lighting 

The Centre has been designed  with a good natural daylighting via  rooflights integrated into the  green roof design to help reduce  the use of artificial lighting.

Lighting and conduits have been  cast into the concrete using  proprietary boxes which contain  bespoke recessed or spot fittings.  For flexibility and future proofing  additional boxes have been  provided on a grid based system  throughout the building so the  light fittings can be moved around  to suit future internal layout  changes as required.  The lighting is generally a mix of  high efficacy metal halide fittings  and LED feature lighting. Within  the interpretive exhibition area  fittings are fast-response low  voltage IRC tungsten display  lighting fittings linked to a Dali  lighting control system to allow  scene changing for the dynamic  multi-media displays.  Emergency lighting is via a  central static inverter system.  The emergency luminaires are  also used for quick-response pilot  lighting for safe access when the  building is not open. Back of  house lighting is via T5 high  frequency fluorescent luminaires  and PIR automatic lighting  controls are fitted to the back of  house areas and public WCs.

Heat Recovery 

The Centre incorporates the  following heat recovery systems:  • Back of house ventilation –  mechanical ventilation with heat  recovery  • Catering refrigeration – all major  refrigeration equipment is cooled  by the primary (brine) GSHP  circuit which contributes to Centre  heating in winter.  • IT / Comms racks are cooled by  the cooled by the primary (brine)  GSHP circuit which contributes to  Centre heating in winter.  • Use of the primary (brine)  GSHP for comfort cooling  purposes during summer  recharges the GSHP collector for  winter use by seasonal heat  recovery / storage  • Heat is extracted from the grey  water recovery system from  washbasins and used to generate  DHW primary LTHW at the same  time as cooling the recovery  water to prevent microbiological  growth. The warm water also  increases the COP and efficiency  of the DHW heat pump. This is  achieved via 300m of ‘slinky’ pipe  in the recovery tank as photo  below.

Electrical Services

  The main supply intake is rated at  145 kVA to include for the  electrical heat pump load and  electrical catering equipment. An  emergency generator connection  point has been provided.  Planning restrictions preclude the  installation of a fixed stand-by  generator and the National Trust  will hire a generator as required.  Comprehensive sub-metering  has been provided, including  separate metering for the catering  which is franchised.  Electrical floor boxes with power  and IT/comms outlets have been  provided in a 3m x 3m grid in the  floor to allow for flexibility and  future internal layout changes.  50% of these electrical points are  concealed under the stainless  linear floor grilles in non-active  sections and the main electrical  distribution routes follow the line  of the grilles for maintenance  access.  Fire alarm and PA points have  been cast into a grid in the roof  slab using proprietary boxes and  conduit in a similar fashion to the  lighting.  Incoming IT cabling and links  between the adjacent Causeway  Hotel and Innisfree (overflow car  parking) are fibre-optic.  The IT system also interfaces with  the radio system covering the car  parks, pathways and stones.  A twin electric vehicle charging  station has been provided in the  main car park – one of a number  of designated key locations in NI.  Even the hand dryers have been  carefully selected for optimum  performance and efficiency, with  the lowest drying time available  (10-12 secs) and a heated high  velocity air jet at 224 mph, giving  a high green rating of 3.8.

Water Conservation  and Management 

The Centre has the highest  standards of water conservation  and recovery.  With over 5,000 visitors on a peak  day and virtually all of them using  the toilet facilities at least once,  the load on the local water  infrastructure and annual water  consumption is potentially very  high.  The following water conservation  and management features have  been incorporated by the M&E  Consultants:

• Low water dual flush WCs – 4  litre / 2.8 litre

• Waterless urinals – downdraught  type specified as the frequency of  use is too high for the standard  cartridge type

• Rainwater recovery from green  roof and rooflights used for toilet  flushing

• Automatic taps with quick  response shut-off

• Grey water recovery from  washbasins in the toilets used for  toilet flushing and roof irrigation

• Condensed water from earth  pipes in summer is recovered and  recycled.

For further information, please  contact Gary Bennett of Bennett  Robertson Design,  Tel: 028 9076 0050