*3.2. Housing Adaptations and Heat Exposure*

The distribution of average indoor temperature exposures for a 2030s summer when *Tmax*,*out*,*<sup>d</sup>* exceeds 23 ◦C can be seen in Figure 2, before and after various energy efficiency, heat mitigating, and behavioural adaptations. Individual energy efficiency retrofits generally do not lead to a significant increase in temperature exposure, with the exception of internal solid wall insulation which causes a median temperature increase of 0.1 ◦C (range: −0.4 to 0.9 ◦C) in solid-walled dwellings. While individual fabric interventions to not lead to a significant increase in median temperatures, the cumulative effects of different energy efficiency interventions on permeability is reflected in an increase following the full retrofit of all buildings in the stock (median 0.2 ◦C, range: −1.0–1.7 ◦C). Full retrofit is predicted to reduce 2030s energy use by 25.5% relative to the current stock, and individual retrofits show comparatively more modest reductions in energy use for space heating. This energy saving is due to reduced ventilative and fabric heat losses only, as changes to heating systems are not modelled. Shutters are able to significantly reduce indoor temperature exposure across the stock (median: −1.4 ◦C, range: −4.1–0.2 ◦C), and lead to a small increase in space heating energy consumption as the absence of solar gains means heating is occasionally required to meet setpoint temperatures.

Decreasing the surface absorptance of the external surfaces led to a smaller reduction (median: −0.5 ◦C, range: −1.5 ◦C–0.6 ◦C) as well as an increase in space heating energy use of 4.1% during the 2030 heating season (September–May). Regarding occupant behaviours, keeping windows open when internal temperatures exceed 18 ◦C had a modest impact on reducing temperatures compared to the threshold of 22 ◦C modelled in the 'current' stock (median: −0.4 ◦C, range: −1.1–0.3 ◦C). The largest risk-factor for heat exposure is keeping windows closed at all times (median 1.4 ◦C, range: 0.1–3.4 ◦C).

**Figure 2.** Density plots of the average indoor temperature when *Tmax*,*out*,*<sup>d</sup>* exceeds 23 ◦C during the 2030 summer following energy efficiency, heat, and behavioural adaptations. The red vertical line shows the median for the current (unadapted) stock (26.3 ◦C).
