AIC's 53rd Annual Meeting

In 2023 the National Portrait Gallery in London (NPG) reopened to the public after undergoing the most extensive transformation of the building since the Gallery first opened its doors in 1896. The project, known as Inspiring People (IP), comprised a complete redisplay of the Collection, significant refurbishment of the building, the creation of new public spaces, a more welcoming visitor entrance and public forecourt, and a new learning centre.

One of the key aims of the building project was to enhance the visitor experience by the controlled re-introduction of daylight into spaces where windows had previously been blocked. At the same time, the new displays diversified the type of artworks on display, incorporating significant numbers works on paper and photography in the permanent galleries alongside paintings and sculpture. 

The engineering and design consultants Max Fordham were engaged to support the new vision for the Gallery. They created solar maps or ‘digital twins’ of the galleries simulating the natural light over a year using existing measured data as well as predicted future climate data. 

The modelling used a limiting illuminance (lux) and an annual exposure limit for artworks (klux.h per year) related to the light sensitivity of objects categorised as: 

2- Low responsivity (e.g. oil and tempera painting, wood, ivory) with a 200 lux limiting illuminance and 600 klux.h per year exposure limit, and 

3- Medium responsivity (e.g. prints and drawings, manuscripts, miniatures with a 50 lux limiting illuminance and 150 klux.h per year exposure limit). 

The use of annual exposure limits was new to the conservation team and required a shift in thinking as it did not align with the existing light sensitivity categories and exposure limits for objects at the NPG.

The digital twins allowed different methods of daylight control to be tested, including UV film, blinds, scrim and alternative settings for existing louvres. A range of different solutions were designed for different galleries, allowing curators to position category 2 light sensitive objects within the general gallery spaces. 

While modelling and planning was extensive, re-introducing and managing increased daylight across a range of differing display spaces is a complex undertaking requiring ongoing re-evaluation and adjustment. After opening, light monitors were placed into the galleries where category 2 objects were on display in spaces with natural light. Positioning of the sensors was a balancing act between aesthetic considerations for the re-displayed collection, and effective data gathering. With a year’s worth of data gathered since re-opening, these measurements can now be compared to the modelling by Max Fordham to assess the accuracy and review the parameters if necessary. 

This paper will discuss the challenges posed by the new approach to light management at the NPG and also the role of cross-team collaboration in the management and delivery of lighting projects.