Fig. 3: Case studies of the GISE framework in Berlin, Germany.

A Roll-out of heat pumps. The share of new residential unit permits in Germany with fossil-based heating systems dropped from 90% in 2000 to around 26% in 2021, while the share with heat pumps grew from 1% to 44%¹³⁸. However, only 2% of homes in Berlin use electric heat pumps¹³⁹; mostly in single-family homes¹⁴⁰. Further, one quarter of residential heating systems in Berlin are aged 25 years or older, and the average age is 18 years¹³⁹. This presents an important opportunity to rapidly replace old fossil heating systems and increase the use of heat pumps for residential heating. This needs to be fostered by respective incentives for owners and legislation. While Germany’s Building Energy Act¹⁴¹ forbids installation of new oil boilers in new and renovated buildings from 2026, and all newly installed heating systems from 2024 must integrate at least 65% renewable energy where possible, gas heaters may still be installed as secondary systems or in replacements where heat pumps or district heat are considered infeasible. Policies and strategies must explicitly exclude oil and gas from all new buildings and replacements. If fossil heating systems are installed today, they will become stranded assets, needing replaced long before their technical end-of-life (e.g. a gas boiler installed in 2025 with a lifetime of 25 years would normally remain in use until 2050) if climate targets in the building sector are to be met. B 15 min City. A positive urban vision is the 15-minute city that enables citizens to meet their daily needs within a short walk or bicycle ride from their homes. Interventions to reach this goal include phasing out fossil-fuel cars, provide affordable and good public transport, radically reduced on-street parking, which also provides the opportunity for high-quality active travel infrastructure. This can be facilitated by changes in the taxation and legal framework at a national level, as well as providing street space to smart, electric, and active mobility (services) and the infrastructure these require. This requires the alignment of a multitude of stakeholders; some obvious (e.g. residents, urban planners, etc.), other perhaps less so (e.g. local businesses; urban logistics providers). These steps also lead to co-benefits for well-being and public health in terms of e.g. cleaner air and safer urban space. C Heat Wave Resilience. Urban communities and infrastructure play an important role in combating heat stress through representing the enabling factors to reach the desired climate protection targets. This requires a collaborative effort and interventions of stakeholders at all levels of society (e.g., urban planners, residents, utilities, housing sector, and various public corporations). Interventions to reach milestones towards heat mitigation goals require: (i) Combination of increased urban green coverage (e.g., street trees, local urban parks, green roofs) and a reduction in the impervious surfaces cover; either through replacement with vegetation cover or high albedo material (e.g., car parks and sidewalks) (ii) Identification of city vulnerable spots and population, which are most susceptible to adverse health impacts during heat waves (iii) Promotion of environmental transport modes (e.g., cycling) along with investments in providing the required infrastructure (iv) Investments in community awareness and R&D. Resulting co-benefits will reflect on both climate and public health sector and can support equity in living conditions and accessibility to green public spaces.