Heritage buildings can comprise a large share of the existing stock but are seldom considered in mainstream sustainability discourse. Rooftop photovoltaics (PV) are one effective strategy for energy retrofits of heritage buildings as the on-site renewable energy generation can contribute to decarbonizing the operational energy demand of the building. However, if rooftop PVs were considered sustainable as a default in the past, new evidence has shown that their contribution to a low-carbon outcome is much more nuanced. To offer a net carbon benefit compared to the status quo, rooftop PVs must be analyzed from a life cycle perspective. Savings from lower carbon energy in the operational phase are not sufficient. These must also be large enough to outweigh the embodied carbon of the rooftop PV's manufacturing, installation, maintenance, and final disposal. This paper presents a case study of the rooftop PVs installed on King's College Chapel in Cambridge. A thorough primary data collection enabled reliable estimates of operational energy generation and the PV's whole-life embodied carbon. Results show a net carbon benefit from installation in the first solar panel lifecycle with a payback period (PBP) of 21 years. The embodied carbon is never paid back in the second and third PV lifecycles. The results show that rooftop PV panels on heritage buildings can contribute to lowering the building's carbon footprint, but this should be verified on a case-by-case basis. There is a significant chance that adding PV to a heritage building roof creates more carbon than it offsets.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)