Natural light design for an ancient building: a case study

This paper presents a qualitative and quantitative approach to natural lighting design for historical buildings, in this particular case study used as a public library. The interior design proposed for the old library of Palagio di Parte Guelfa in Florence, was based on solar radiation control and advanced daylight system application (two light shelves, a sky light and two light pipes) without modifying the architecture and structure of the building. The main objectives of the project were to increase lighting energy savings due to less artificial lighting system utilization, the corresponding daylight illuminance levels at long indoor distances from the windows, and to improve the uniformity of luminance distribution and illuminance gradient across the work-plane and at different inside levels and a comfortable lighting environment under variable sun and sky conditions throughout the year. A method was also proposed for evaluating daylight distribution in rooms of ancient buildings with small transparent surfaces and high thermal inertia, using solar shadings and light redirecting devices. It enabled a simplified hourly evaluation of the daylight utilization with reasonable accuracy and calculation speed and, because it was coupled to a simplified thermal model, evaluation of the impact of daylight utilization on hourly temperatures, heating and cooling demand.