Engineering enlightenment.

While working with some of the world's leading contemporary museum and gallery designers, London-based Arup Lighting have identified two distinct streams in the pursuit of passive daylit solutions.

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'Daylight is of decisive importance when experiencing architecture. It is constantly changing. While an architect can fix the dimensions of solids and cavities, designate the orientation of a building, specify the materials and the way they are detailed, and describe precisely the quantities and qualities of a building before a stone has been paid, daylight alone is beyond their control. So how is it possible to work with such a capricious factor, and how can it be utilized artistically?'

Steen Eiler Rasmussen. Experiencing Architecture an edited extract

The first public galleries and museums to be purpose built date from the early nineteenth century, and were entirely dependent on daylight. More often than not, they were based on classical models temples and palaces and were large, lofty and symmetrical. Today things are no longer as formulaic.

As contemporary exhibition spaces break these established models as the art-space is replacing the gallery in seeking to manipulate daylight to meet the specific and onerous technical targets that the modern exhibition space demands, it is becoming increasingly necessary for architects to consult engineers to accurately simulate a wide range of daylight conditions. But when working with people as different as Renzo Piano with his inventive component trickery, and Daniel Libeskind with his highly specific fractured geometries, how are their skills best integrated into the design process?

Arup Lighting have collaborated with a wide range of architects including Piano and Libeskind, and Director Andrew Sedgwick describes their role as a response to either known or found conditions. As a known condition, at the outset of a project with Piano for example, an attitude to light will be prescribed, which when resolved by a component helps to inform the identity of his architecture as at the Beyeler Institute. On the other hand, Libeskind manipulates light as if it were a physical material, giving the engineers highly specific found conditions to respond to. So while with Piano they know the condition they are seeking to create and use their expertise to help refine the performance of a component or a piece, with Libeskind they are given a daylit scene to analyse in order to quantify its performance and appropriateness as an exhibition space, making recommendations where necessary.

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Piano

When considering the two principal gallery spaces at the High Museum of Art in Atlanta, Georgia. Piano's aspirations were clear. Within a four foot grid, using a repetitive passive lighting component. Piano wanted to optimize the amount of diffuse daylight that entered the spaces. He wanted uninterrupted views to the sky, and of critical importance to the conservation of exhibits, all direct sunlight had to be excluded. So within this known brief the design team began to model, simulate and refine the composition of the skylight components: a static element that comprised a precast cylinder know as a 'Cannon' (incorporating collapsible interstitial dim-out and black-out shading layers), a clear glass envelope, and a sculptural GRP shading cowl. While early computer models and seasonal animations demonstrated that the final composition met both the architect's visual criteria and the technical lighting specification, when the architect started to distort the perimeter shading cowls to integrate them with the cladding on the elevation, a second condition was highlighted that needed further analysis. This resulted in an area of fritting being added to the glazed lid of the cannons to resolve an unacceptable condition that was made apparent from simulations and the construction of a full-scale mock-up. Despite huge advances in simulation techniques, a full-size mock-up is still considered to be an essential part of the design process. Not only does it serve as a useful model to test the effect of light on internal linishes, but, more critically it gives the architect and the exhibition curators the opportunity to truly experience the nature and quality of the space that is never adequately sensed in virtual reality. Refinements can then return to complete the feedback loop, with adjustments being re-tested digitally before final decisions are made. The mock-up also enables more subjective decisions to be made, such as to what degree secondary reflections are acceptable, as was the case with the diagonal striations seen on the walls beneath the soffit; subtleties that until experienced could not be adequately understood.

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Libeskind

In contrast to the iterative process of working with Piano, Arup Lighting's role when working with Daniel Libeskind may initially seem more peripheral. With geometries set by the architect, fundamental changes are rarely made, and arguably their input has less of a direct impact on the resultant form of the architecture. Yet, when dramatic spaces such as those created by Libeskind are needed to perform a practical role for exhibitions, it is essential that exhibition designers know where the daylight is throughout the year. So, by calculating the sunlight hours and annual exposure to daylight, the exhibition designers and curators can be more informed in developing their distribution strategy. For, while Libeskind would inevitably have tested his compositions himself to understand the visual effect of light falling on internal surfaces (a process which physical models are perfect for as light is scaleless), a more sophisticated animation technique is required for more quantifiable analysis before the lighting consultants can make recommendations to introduce controls where necessary (especially in spaces where the contrasts between low daylight factors and dramatic shafts of direct sunlight are common).

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Throughout their work, Arup Lighting try to balance the architectural aspirations of designers with the practical requirements of the curators. The success of their input often relies on the ability to resolve the conflicts that arise, such as spatial flexibility versus spatial composition. But, it would seem that there is a shift in the current market that recognizes the need to return to natural lighting solutions, and in a number of cases passive control techniques. Instead of pursuing the black-box track and spotlight technique, which until recently has dominated American institutions, naturally daylit exhibition spaces are having a renaissance. With better colour rendering than artificial light, and with the dynamic ever-changing nature of daylight and the environmental bonus of energy efficiency, the benefits are clear. Despite technological advantages, the human eye will always have the ability to perceive the subtle qualities of a light source. Daylight is impossible to simulate in any convincing manner. So, the move to exploit ambient natural lighting and to reduce the reliance on artificial light should be welcomed, which in turn will increase the necessary input from enlightened engineers.

Architects

Renzo Piano Building Workshop

Studio Daniel Libeskind

Lighting Consultants

Arup Lighting: Andrew Sedgwick, Arfon Davies, Florence Lam, Tim Hanson