John Mardaljevic, Professor of Building Daylight Modelling at Loughborough University, collaborated with Cannon-Brookes Lighting and Design to map the distribution of natural light in National Trust properties – and its effects on the artefacts they house.

Over the last 20 years there has been a reassessment of the function and evaluation of natural illumination in buildings, this is the first study of its kind in an historic space.

Keen to balance visitor enjoyment with the preservation of paintings, textiles and furniture vulnerable to light fading and ageing, the National Trust approved the study at Ickworth House in Suffolk.

The research deployed a novel technique, high dynamic range imaging (HDRI), to measure where natural light falls at different times throughout the day and changing seasons.

A computer-controlled wide-angle camera photographed the interior of Ickworth’s Smoking Room every 10 minutes. These photographs were converted into measures of light levels to produce a cumulative luminance image.

This image showed the distribution of light exposure across a range of surfaces within the room, and underpinned a comprehensive evaluation of the illumination conditions over long periods.

In addition, the project used climate-based daylight modelling to predict how long-term daylight exposure could change if, for example, a building’s opening hours were increased.

The research has provided the National Trust with a better understanding of natural light, and its likely impacts on valuable historic objects in specific sites.

Dr Nigel Blades, Preventive Conservation Adviser at the National Trust, said:

“The research is enabling the National Trust to understand, better than ever before, the fall of daylight onto light sensitive surfaces in historic showrooms. Based on the research, we will fine tune our use of daylight to minimise the rate of change in light sensitive objects, while providing sufficient daylight for visitors to enjoy our collections.”

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