<b>ABSTRACT</b></br>

It is worldwide accepted that climate change is affecting cities and that the conservation of the

cultural heritage contributes to sustainable development. However, despite the high level of interest

and research in climate-change risks, a holistic understanding of the risk that heat waves and heat

urban island phenomena present to urban cultural heritage is noticeably absent from literature.

Aside from understanding the impacts that heritage faces with climate change, the consideration of

loss of heritage and cultural values and assets due to extreme heat waves will promote the resilience

and sustainability of both social and built environmental systems.

The aim of this paper is double, first to identify key performance indicators for risk assessment

methodologies that address both the elements of historic urban areas as a system and the potential

impact of prolonged heat waves. Second, this study aims at developing a categorization for both

buildings and urban spaces within historic urban areas regarding their vulnerability to heat waves,

which will be the basis for further risk assessment. For this twofold purpose, the interaction between

urban spaces, heat waves, and the urban heat island is addressed as well as the vulnerability and

behaviour of traditional materials and building typologies.

To define the elements that conform historic urban areas, the system is addressed from two

perspectives, as an urban system, and as a historic area. At the same time, for a holistic approach,

every element of the system is assessed, distinguishing between socio-economic, cultural,

governance (services and resources) and physical (gathering tangible characteristics of all

infrastructures, elements and buildings) aspects. The indicators and categorization are, therefore,

essential for the evaluation of the impacts of heat waves and the urban heat island on the elements

that conform the system of the historic urban area.

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<b>ACKNOWLEDGEMENTS</b></br>

The authors wish to acknowledge funding from the European Commission through the SHELTER project (GA 821282), as well as the support of the <b>SAREN</b> research group (IT1619-22, Basque Government) .