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Lighting Cultural Heritage is a complex task: light is necessary for the act of seeing, it can even enhance the visual experience [ 1 , 2 ], in addition proper lighting can significantly cut down energy consumptions [3] , but on the same time it has detrimental effects on exhibits, especially daylight. In order to safeguard the exhibits from damages, national and international standards provide specific recommendations for exhibits’ exposure, based on their photosensitivity category. These recommendations are the annual luminous exposure(LO) and the Maximum Illuminance Level (E max ), museums’ curators have to verify that the display lighting conditions comply with the standards. Historical buildings are often converted into museums but, as their original purpose was different, the lighting conditions are often inadequate (e.g. too much uncontrolled daylight), therefore the lighting conditions’ adequacy of the space should be assessed [4] . As the name suggest the annual luminous exposure requires an annual monitoring campaign, unfortunately it often happens that exhibits have been exposed incorrectly for prolonged periods, and therefore it is very important to evaluate the need of a fast intervention. In this casuistry a prolonged measurement campaign is not acceptable. Simulations can help running a great number of analysis while reducing the length and expenses of a measurements campaign, however their previsions must be validated. This paper provides the data acquired through measurements and simulations inside the Cetacean Gallery of the Monumental Charterhouse of Calci, near Pisa (Tuscany Region, Italy). The data comprehends horizontal and vertical illuminance measurements, recorded on December the 6th, and simulations run in Grasshopper with the plugins Honeybee+ and Ladybug . The data are related to the research article entitled “Application of climate-based daylight simulation to assess lighting conditions of space and artworks in historical buildings: the case study of Cetacean Gallery of the Monumental Charterhouse of Calci”, published on the Journal of Cultural Heritage [5] .

Alternative environments to real-life have been in recent demand in regard to lighting design and in museums. In this study, the effectiveness of the perception of the museum space in simulations or virtual-based environments is studied. Answers to a questionnaire regarding lighting in four different visual experiences are compared: Real-life, virtual-video-based, virtual-photo-based and virtual-render-based. A total of 117 participants were divided into four visual experience groups. Each group answered the same lighting related questions for four exhibition halls in the Natural History Museum of the University of Pisa (Italy), which is housed in the Monumental Charterhouse of Calci. The answers were analyzed using ANOVA and a T-test. The results show that virtual experiences can be acceptable alternatives to real-life experience as the answers were indifferent in more than half of the criteria, and no criterion was affected significantly by experience, regardless of the hall’s characteristics. However, it was found that the hall’s characteristics also had an impact on the perception of the criteria in different experiences. Controlled artificial lighting or uniformly distributed lighting (full day or artificial light) were found to be more indifferent to the experience.

Lighting cultural heritage is a complex task that requires considering the conservation needs of the exhibits and visitors’ visual comfort. However, these needs are often in contrast. In addition, whenever the exhibitions are displayed inside historical buildings, the task further complicates, as lighting designers must face and respect the architectural character of the host building. They have two mean of work: static and dynamic analysis. The former uses the Daylight Factor (DF) while the latter requires a prolonged and expensive measurement campaign. Both analyses present advantages and shortcomings: the DF approach is easy and fast, but it implies many oversimplifications whereas the annual approach provides accurate results but is time and money-consuming. In this paper the authors analyse a case study with both methods. The case study is the Cetacea’s Gallery of the Charterhouse of Calci (PI). The findings of this research demonstrate that the annual approach is preferable, despite its costs, and that the static approach should be used just for first instances analyses. The research pointed out the necessity of a standardized procedure of evaluation that would allow lighting designers to confront possible interventions and find the most adequate to solve the conservation and comfort issues of the case in exam.