Carbon footprint of biostatic, targeted ornamental lighting and related cleaning service for sustainable conservation of architectural heritage

Studies evaluating the sustainability of architectural heritage conservation are scarce. Given the impact of nocturnal ornamental lighting on biofouling, in this case study, the carbon footprint and economic cost of the lighting and associated biofouling control were evaluated in a historic building in the heritage city of Santiago de Compostela (NW Spain). The novel CromaLux LED lighting system was first used in this UNESCO World Heritage city in 2021, and its impact on both services (lighting and cleaning) has already been reported. The expected improved environmental performance and the associated costs can therefore now be quantified. To this end, three ornamental lighting systems (metal halide, white LED, CromaLux LED) and five cleaning methods (laser, water vapour, Biotin T®, Biotin R® and reinforced ethanol) were compared. CromaLux LED outperformed both the traditional metal halide and white LEDs systems (reducing the lighting service carbon footprint by 80% and 20%, respectively). The best-performing cleaning methods were those based on laser (0.49 kg CO2-eq) and reinforced ethanol (2.76 kg CO2-eq), although the ethanol-based method is more costly than the others (up to 21.41% more). The reduction in biofouling yielded by CromaLux reduced energy consumption by up to 16.83 kg CO2-eq. If implemented at city level, the CromaLux LED system could potentially yield annual savings of up to 3.64 tonnes of CO2-eq and €1,269.91. The findings thus confirm the advantages of CromaLux for improving the environmental and economic sustainability of lighting and cleaning architectural heritage.