DAYLIGHTING | MUSEUMS AND GALLERIES Max Fordham used a digital twin during the renovation of the National Portrait Gallery The digital twin was able to calculate the distribution of the sun and skylight inside the National Portrait Gallery every 15 minutes across the course of a test year, accurately tracing more than 200 million rays of light to build up a complete picture of daylight levels inside every gallery space Lighting up the gallery Advanced techniques in lighting analysis are allowing designers to reintroduce daylighting into galleries without damaging the exhibits or causing visual discomfort to those viewing them. Max Fordhams Nick Cramp highlights the benefits T here are many benefits to bringing daylight into museums and galleries from improving the quality of lighting and saving energy and emissions, to providing a healthy environment that fights the gallery fatigue visitors can otherwise face. Though many of our museums and galleries were designed to be lit primarily, or even exclusively, with daylight, those openings have often been blocked up over the years because of concerns over conservation and light damage. The unintended effect of these measures has been to lessen the connection with the outside, making orientation more difficult and depriving occupants of the wider benefits of natural light. Max Fordham is routinely tasked with safely reintroducing daylight into existing galleries and museums, as well as ensuring that we make the best use of natural light and views in our new-build projects. The challenge is to create beautifully day-lit spaces that maintain the standards of conservation needed for the utmost care of precious exhibits. Our constantly changing climate means daylight levels are inconsistent and we need to aggregate them over a long period of time to understand them properly. The technology needed to undertake these kinds of virtual studies, as well as to validate them through long-term onsite monitoring, has only been developed Different options for daylight control were tested using the digital twin, with parametric optimisation employed to discover the perfect way to reuse the otherwise redundant rooftop louvre system recently, and is allowing us to use daylight much more extensively. A good example of this is at the Hayward Gallery on Londons South Bank, where we were able to restore the iconic roof pyramids and return daylight to the galleries after an absence of 30 years. Advanced analysis techniques now allow us to understand more precisely the distribution of natural and artificial lighting in every space, and we are able to give curators a much larger display area without increasing the size of the building. This, in turn, lessens our reliance on energyintensive conditioning systems and allows us to greatly reduce the embodied carbon emissions of museum projects, through reuse and restoration, rather than demolition and rebuilding. In the Queens Diamond Jubilee Galleries at Westminster Abbey, our detailed daylight modelling enabled the exhibits to be carefully placed around the path of incoming daylight. They filled previously unused spaces at balcony level and created a whole new gallery without the need for an extension. Max Fordham built on this experience and created a digital twin of the National Portrait Gallery during its recent renovation, simulating the contributions of sunlight and skylight to the internal spaces over the course of a test year, using existing measured and future climate data. To achieve this, we generated 8,000 simulations, each requiring the accurate tracing of more than 200 million rays of light. 40 December 2023 www.cibsejournal.com CIBSE Dec 23 pp40-41 Designing with daylighting Supp.indd 40 24/11/2023 13:05