Can urban residential buildings adapt to heat without air conditioning?

Extended abstract 8-085-26

Rising temperatures and frequent heatwaves intensify summer thermal discomfort and cooling demand, especially where the Urban Heat Island (UHI) effect amplifies exposure. However, national-scale energy models often overlook building-scale thermal processes, urban–rural heterogeneity, and passive cooling effectiveness. This study investigates: (1) the potential of passive strategies to reduce discomfort in urban dwellings; (2) UHI interactions with building characteristics; and (3) implications for future active cooling adoption.

We develop a modelling framework combining an extended resistance–capacitance (RC) thermal model with the national-scale residential-sector microeconomic model Res-IRF. The RC model represents radiative exchanges, roof albedo, solar protection and ventilation, and introduces an urban–rural segmentation through differentiated climatic boundary conditions accounting for UHI effects. Passive adaptation strategies are modelled individually and in combination, including cool roofs, solar shading and night ventilation. The framework is parameterised using high-resolution climate data and building typologies derived from the TABULA database.

Figure 1 shows that passive cooling strategies significantly reduce thermal discomfort, measured through cooling degree hours (CDH), with stronger effects in urban contexts. In the baseline case, urban CDH levels are more than twice those observed in rural areas. Solar protection and cool roofs provide substantial reductions, while their combination leads to reductions of up to about 50% in urban areas. The UHI effect therefore both increases baseline discomfort and amplifies the benefits of passive measures.

Coupling the RC model with Res-IRF allows us to assess system-level implications. In the Île-de-France climate zone (H1a), the total adoption rate of air-source heat pumps for cooling is projected to reach around 50% by 2050 under baseline assumptions but falls to about 42% when roof albedo improvements are introduced. The magnitude of cooling adoption reductions also differs between urban and rural contexts, reflecting heterogeneity in urban morphology and building typologies. While portable cooling adoption declines in H1a, other climate zones such as H1c and H2b show renewed growth after 2037, also indicating heterogeneous regional dynamics under climate change.

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