London Climate Action Week 2026

Across Europe, the economic toll of climate-driven disasters has multiplied over the past decade, and our current path points the same way. Thankfully, as people across several European countries live through these extremes, public opinion shifts, and those shifts push cities towards action. London answered mid-week with Heat Ready London, its first citywide heat plan — setting out how to protect the most vulnerable and make homes, hospitals, transport, and public space ready for hotter summers. On top of that, energy price shocks in recent years have driven households toward heat pumps and solar power to lower their bills and stabilize costs. The pattern I see is clear: cities have become places where ambitions to address climate change translate into action.

Consider the numbers regarding reuse. Up to 80% of the buildings that will be in use in 2050 already exist today. Meeting our climate goals, then, is largely a question of what we do with them — retrofitting, adapting, and bringing vacant stock back to life. That work asks more of us than new construction, with unforeseen challenges and costs along the way. Yet it delivers greater long-term value by preserving embodied carbon, retaining the social and cultural fabric of neighbourhoods, and extending the life of existing assets. The task now is to build the incentives and blended-finance models that make reuse the obvious path. Cities are already showing how: São Paulo's Requalifica Centro programme offers tax incentives—including a three-year property-tax exemption—to encourage the retrofit of older buildings, while Paris's 2024 bioclimatic planning rules prioritise retaining and adapting existing buildings over demolition.

Housing came up in conversation after conversation across the week. At the Barbican — itself a 1970s modernist model of dense, mixed-use living that has aged into one of London's most coherent neighborhoods — the Holcim Foundation supported C40 Cities to host a panel built on a clear premise. This was the notion that sustainable urban regeneration, reusing and upgrading the building stock a city already has, can expand affordable housing supply and cut emissions at once. The session drew the full value chain into one room: mayors from Phoenix to Barcelona, the investors and developers who finance delivery and urban planners.

Two points from the conversation stayed with me. Delivery at scale needs city halls to bring in people who speak the language of investment — public servants fluent enough to structure deals and draw private capital toward public goals. And regeneration makes sound financial sense: reusing land a city has already serviced puts its existing roads, schools, and hospitals back to work, sparing the new infrastructure that greenfield housing always demands.

One of the most compelling ideas to emerge during the week was that housing should be treated as infrastructure.  Residential development is judged on returns within a few years; infrastructure is judged over decades — and it is infrastructure that shapes a city's resilience, productivity, and quality of life for the long term. If we fund housing the way we fund infrastructure — as patient, long-horizon assets — then deep retrofits, office-to-home conversions, and the renewal of aging social housing all become viable investments, even though their returns accrue over decades. Policy is beginning to catch up. Initiatives like HouseEurope!, which the Holcim Foundation has supported, are making the case for a right to reuse that lowers housing costs and carbon together.

The week ended fittingly, with the Foundation's Board at Thames Materials, a recycling center in west London, where construction and demolition waste is sorted, crushed, and reprocessed into high-quality materials for new buildings and roads. Meeting the people whose daily work is to give those materials a second life left me more determined than ever to support this approach. When it comes to the built environment, the resources for more resilient, more affordable cities already surround us. What we need now is the vision, the partnerships, and the investment models to reuse and renew them at scale — and to back the citymakers already doing exactly that.