Following a competition The National Trust commissioned Gareth Hoksins Architects in 2004 to design the new 2400sqm visitor centre. The new building is three times the size of the existing facilities it replaces and is designed for up to 250,000 visitors a year, housing interpretation of the battle along with educational and conference facilities, a 240 cover café and restaurant, a shop and staff/ancillary accommodation. Whilst the existing visitor centre was built on archaeologically sensitive ground the new centre is moved away from the battlefield lines, ensuring that the new building’s location would not disturb graves or artifacts. The new building is anchored between an existing field wall and a new gently rising berm which is aligned to the rearmost government lines, screening visitor traffic from the battlefield and delivering visitors onto a planted roof terrace for a unique view of the site. The building and berm act as a portal to the site, allowing the visitor the choice of a stay under the scalloped roofs of the restaurant before or after an interpretive journey through the exhibition with views out to the landscape at key points culminating on the roof terrace. When the centre is closed the site can be accessed via the portal formed by the bridge to the roof, passing the memorial wall which offers a visual interpretation of the historic site and its status of a war grave and burial ground for over 1200 people. The building is located within a conservation area containing a number of scheduled ancient monuments. The site is extremely sensitive and of national and international significance; therefore planning consultations involved Historic Scotland, Scottish National Heritage, Royal Fine Arts Commission as well as The Highland Council which set strict parameters for heights, views, and materials. The building is constructed in steel frame with concrete floor slab and highly insulated timber walls and roofs. External walls are mainly clad with untreated Scottish Larch from a nearby estate, other areas are clad with local Caithness Stone and field stones salvaged from the site. Internal timber linings are made from untreated Scottish Larch with all other joinery made from oiled British Oak. Large internal and external floor areas are covered with local Caithness flagstones. The roof is a covered with a TPO membrane. More than 1000sqm are used as a public viewing terrace and are covered with an intensive green roof system. The under floor heating is powered by a bio fuel boiler fed from the estates of the local forestry commission. Most of the building is natural ventilated via roof lights - which also maximise the use of natural light - or high/low level grilles and stack vents. The building was procured as a two stage design and build contract (amended JCT 1998 With Contractor’s Design) with architect and structural engineer novated at second stage. The contract sum for the building was £5m including £1m of external works. The contract sum for the exhibition was a further £1.5m, which was added to the main contract with Morrison Construction Ltd (Highlands & Islands division). The global project cost for the National Trust was £9.4m.
The building form, has a small surface:area ratio to minimize heat loss and its low form reduces exposure to northerly winds. Orientation and roof form are manipulated to maximize glare free daylight and natural ventilation. The large deep plan interpretation area did not require natural lighting to the same extent so here the roof functions as an viewing platform colonized by indigenous plants to retain biodiversity. Roof access is achieved via an 80 metre inclined planted berm/screen containing site spoil which would otherwise go to landfill. At the restaurants, kitchen and education room, the curved roofs distribute north east clerestorey light evenly and extend to overhang the south east glazed terraces for shading and shelter. A long north facing clerestorey to the orientation and interpretation areas and aftermath gallery allows both glare free lighting and views out at key points. The large area of south facing glazing illuminating the Derby Council display is shaded by external louvres which are incorporated into the larch cladding. The challenge of the Interpretation Area brief was to design a naturally ventilated building that could respond to extremely high visitor loads during summer high season. A passive ventilation system was developed, combining opening windows and low-level vents, with high-level ventilation via parapets and roof cowls. The system is generally wind-driven, orientated towards the battlefield/prevailing wind. Low speed plate fans, concealed within the roof cowls, provide increased airflow for extreme conditions e.g. high visitor numbers on a still summers day. Ventilation control is automated, with manual override by the user – to respond to unexpected changes in visitor numbers. There is minimal dependence on artificial cooling - only catering kitchen and WCs. Cooling is required only in the small exhibition AV room, and the manager’s office – both are remote from the façade and contain much IT equipment. The visitor support curved roofs also assist the aim of maximizing natural ventilation via high level clerestories. The building is constructed as a lightweight, high response timber/steel envelope on a massive insulated stone/concrete floor incorporating underfloor heating. Thermal mass evens out temperature swings for the 12+ hour daily occupation and the thermally responsive shell adjusts quickly to occupation. The construction included above Regulation levels of thermal insulation- mineral fibre walls and visitor support ceilings and EPS for roof and ground floor. The planted roof over the interpretation area also contributes some thermal insulation and mass to the fabric of this element. A fully automated woodchip boiler system provides space heating and hot water generation. Woodchips are supplied by the Scottish School of Forestry – harvested from sustainably managed forest within a 10km radius of the building- and should save approximately 55% of the total CO2 output of the building. The boiler uses high efficiency, low emission, technology from Austria. Two small LPG slave module boilers cover peak/low loads during the summer. We believe this to be one of the largest and most sophisticated woodchip heating systems currently operating in a public building in Scotland. Variable speed pump drives lower plant room electrical consumption. Underfloor heating in the exhibition areas (approximately half of the building) will be kept at a lower set-point temperature helping to provide stable conditions for sensitive artifacts, and reduce annual energy consumption.
