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CIBSE Case Study: Optimised Lighting for Art Gallery
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CIBSE Case Study: Optimised Lighting for Art Gallery

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Article from the December 2011 edition of the CIBSE Journal by Florence Lam

The design for the new Hepworth gallery aims to provide optimum light to show off the eponymous British sculptor's works, as well as serving the needs of other, light-sensitive works. Florence Lam of Arup Lighting outlines the approach taken.

With buildings often housing priceless artwork and exhibits, conservation, security and protection are clearly paramount in the design of galleries and museums. Perhaps for many of these exhibits the best way to preserve them would be in a darkened room, but of course that would somewhat defeat the object of a gallery and it's important that they are shown to their best advantage for the benefit of the visitor.

With a long track record working with museums and galleries, design consultancyArup Lighting has been involved with projects ranging from the Victoria and Albert's Medieval and Renaissance Galleries, through to the Malaga Picasso Museum, the New Acropolis Museum in Athens and the Brandhorst Museum in Germany.

The Hepworth Wakefield is one of the most recent that Arup has completed in the UK, opening to the public in May 2011. With an inspirational design by David Chipperfield Architects, it is one of the UK's largest purpose-built art galleries outside of London. It displays the work of sculptor Barbara Hepworth, as well as the City of Wakefield's art collection and exhibitions by contemporary artists, throughout a cluster of discrete trapezoidal rooms on the upper level.

Arup delivered the natural and artful illumination. The design for the new Hepworth gallery aims to provide optimum light to show off the eponymous British sculptor's works, as well as serving the needs of other, light-sensitive works. Florence Lam of Arup Lighting outlines the approach taken architectural lighting design with two goals: to conserve the gallery's temporary exhibitions and to present Barbara Hepworth's 44 original plaster sculptures literally in optimum light. The lighting design principle strikes a careful balance between the long-term conservation of light-sensitive works and the visitors' visual needs. Arup aimed to ensure that each space was designed within the established international standards for limiting illumination, but this was determined in terms of the following cumulative light exposure (a measure which actually determines the rate of deterioration of artwork):

  • Works on paper: 50 to 80 lux, or
  • Oil paintings: 200 to 250 lux, or
  • Sculpture - painted (depending on type of paint): 80 to 250 lux, or 240-750
  • Sculpture - natural finish: up to 800 lux, or up to 2,400

The brief required the design to bring the outdoors in, so daylight can be experienced in the galleries. The lighting concept was to use windows for the views, and skylights to animate the space. The intention was to develop skylight and window designs producing varied daylight distribution across each space, allowing works on paper to be displayed in darker areas, for example, and sculpture to be displayed nearer daylit areas expressing a coherent, curatorial story.

In other words, the space is asymmetric in lighting terms, allowing the curator the freedom to put relevant sensitive and non-sensitive artwork together, rather than the selection being partially dictated by conservation constraints.

The process was begun by applying regional historical weather data to the geometry of each room over the course of a year to estimate the extent of daylight exposure. Arup developed a methodology to assess how a particular geometry/fenestration arrangement responded to daylight. Where the exposure exceeds the allowable levels, shading systems are used to optimise the light for particular scenarios.

To help the curators determine suitable locations for artwork with various light sensitivities, the team developed a daylight mapbook, which gives a three-dimensional representation of the annual exposure prediction for each gallery.

The strategically placed windows within the galleries create visual connections for gallery visitors to the river and surrounding landscape, while allowing people outside to get glimpses of activity inside and of collections on display. The windows use transparent glazing with a clear UV interlayer to protect sensitive works. Openweaved diffusing blinds of 20% lighting transmittance are deployed on sunny days, still maintaining the view outside. When the exhibition is closed, blackout blinds cut out unnecessary light exposure.

The visitor experience is further enhanced by the play of light in the galleries. At the taller end of each gallery, discreet skylights create a daylit backdrop, providing a "stage" for the exhibition. The skylights use laminated glass with a diffusing interlayer that doubles as a UV filter. Adjustable louvres control daylight filtering through the skylights, creating a glow at the top of the wall to draw the eye of visitors entering the room. These are adjusted seasonally, modulating higher light levels between March and November, while maintaining the experience of external lighting variation throughout the day.

Electric lighting in the galleries comprises two lighting elements: concealed cove lighting and track lighting. As daylight fades at dusk, each skylight is subtly illuminated with concealed T5 HO fluorescent luminaires, fitted with asymmetric reflectors to provide ambient lighting after dark. In addition, track lighting is provided to accommodate any art location or wall configuration, allowing for flexibility in illuminating artwork displays.

The sloped ceiling posed a challenge as it was problematic to design a recessed track layout that could ensure uniform wallwashing and optimum incident lighting angles on wall-hung artwork. Zumtobel's Arcos IRC tungsten halogen wallwashers with a special sculptural lens were specified to overcome this. A light reduction lens was added to reduce light output, while keeping the colour at the correct temperature to harmonise the cool daylight temperatures at one end with the warm (3,000K) tungsten halogen.

Arup adopted a minimalist approach to the ground-floor lighting with Viabizzuno's 094 system, customised to provide an integrated lighting and ventilation solution. Cool white T5 HO lamps create crisp runs of parallel light lines across the ceiling for the entrance reception lobby, bookshop and cafe.

The completed building, winner of a British Design Award 2011, has had an enthusiastic response from public and critics alike. In particular, The Independent newspaper has described the galleries as "sublime spaces" and The Hepworth Wakefield as "one of the finest contemporary art museums in Europe".

The £35 million Hepworth Wakefield art gallery houses 44 Barbara Hepworth sculptures and the work of other local artists. The building is sited on the headland of the River Calder at the southern gateway to the city and comprises a cluster of 10 trapezoidal blocks of different sizes, which form the display spaces. All the galleries are on the upper level and have natural lighting.

Project team

Lighting design (daylight and electric): Arup Lighting

Architect: David Chipperfield Architects

Lighting suppliers: Zumtobel (Arcos spots with customised lenses); Viabizzuno (094 system customised to provide integrated lighting and ventilation solution on the ground floor).