Impacts of Heatwaves on the Indoor Microclimate of Heritage Buildings Under Climate Change: A Case Study of the Malatestiana Library

The IPCC has emphasised the increasing impacts of climate change across multiple sectors, including cultural heritage. In response, UNESCO launched the Policy Document on Climate Action for World Heritage in 2023, offering guidance on mitigation strategies for historic sites. Cultural heritage faces risks not only from sudden catastrophic events—such as floods, droughts, and wildfires—but also from the gradual deterioration of buildings and artefacts due to shifting environmental conditions. Climate change further affects the indoor microclimate of heritage sites, including museums, archives, and libraries, which are critical to the long-term preservation of cultural assets. Heritage, including heritage buildings and both tangible and intangible heritages, are subject to changes; therefore, their conservation should be assessed to identify sustainable approaches. This study investigates how climate change and microclimate alterations impact the conservation of historic buildings without modern climate control, using the Malatestiana Library—a UNESCO Memory of the World site—as a case study. The library has preserved a remarkably stable indoor environment for centuries, without the introduction of heating, cooling, or major restorations. A monitoring campaign during the summer of 2024 assessed the effects of extreme heat events on the library’s microclimate, comparing two internal spaces to examine the attic’s role in mitigating thermal stress. Data from the 2024 heatwave are also compared with similar data collected in 2013. Results show a marked shift toward a more tropical indoor climate over the past decade, signalling new threats to the preservation of historic materials. These findings highlight the urgent need for adaptive conservation strategies to address the evolving challenges posed by climate change.