The Effect of Solar Control Films on Enhancing the Energy Efficiency of Historic Buildings

The use of solar control foils (SCFs) is a minimally invasive method that enables energy savings while preserving the original character of historic building facades. This study analysed the energy reduction potential of four types of window films applied to single-pane glazing. A typical office space at the University of Bologna, located in a historic building, served as a case study. Building performance simulations using DesignBuilder and Berkeley Lab Optics software were applied as research tools. The potential reduction in cooling energy consumption by using SCFs can be up to about 35% in humid subtropical (Bologna) and Mediterranean (Seville) climates. A decrease of about 53% can be achieved in a temperate oceanic climate (Paris). Due to the reduction in heat gains from solar radiation, there is an increase in energy consumption for heating by 6% to even 50% and up to a maximum of about 15% for artificial lighting. Financial indicators such as LCC, NPV, and IRR were used to select the optimal option. The recommended solution was an SCF installed on the inside of the window with SHGC of 0.452, a visible transmittance of 0.361, and an inside reflectance of 0.195. Additionally, this study proposes a method for correcting heating and cooling energy demand results calculated based on data for a typical meteorological year and weather parameters measured over the past 19 years. This allows for the validity of energy simulation results by taking into account current climate changes.