Energy efficient lighting of public buildings with architectural restrictions: the challenges and limits of the glare assessment approach applied to the case study of San Salvatore Hall

In some applications, glare might result critical in indoor lighting design of historical buildings, due to the high performance required and the strict architectural restraints. Such issue is discussed referring to a real case study of a relamping project for a deconsecrated church turned into auditorium. In these cases, the standard glare evaluation typically adopted (UGR index) can only provide a preliminary estimation as some of the assumptions are not usually met. So, the level of glare of the current state is estimated by means of a numerical model developed in DIALux Evo (©DIAL GmbH), validated basing on both onsite measurements and the results of a human subject study conducted over the most frequent occupants of the room. The differences between estimated glare (quantitative) and subjective feelings (qualitative) are accounted to assess the glare level in the design stage of the auditorium. The results show that the preliminary estimation of UGR leads to underestimated values, especially when a relevant part of the light is provided indirectly or a change in the lighting system occurs (e.g., from direct and indirect to only direct lamps). Then, a comparison between lighting performance and energy saving for the specific case is proposed.