Heat waves, heavy rains, and prolonged droughts are increasingly common, challenging homes that were built long ago. About 95% of Spanish residences—roughly 15 million buildings—were erected more than four decades ago, meaning they miss the energy efficiency standards introduced in 2007. There is still time to act. Experts advocate a broad program of rehabilitation for buildings that were previously overlooked in favor of new construction. Projections show that, given the exposure of a large number of houses to extreme heat and storms, Spain must invest around 100 billion euros to adapt its housing stock to sustainability criteria with support from international organizations helping to curb climate impacts. Achieving this requires renovating about 350,000 homes each year.
In contrast to peers like France or Germany, where annual rehabilitation rates run at roughly 1.5 to 2 percent, Spain has historically lacked a strong culture of upkeep for homes and buildings, notes Marta Vallllossera, president of the Spanish Supreme Council of Architects Colleges. Statistics from the College of Architects show 25,554 homes were rehabilitated in 2019, a year preceding the pandemic. The lockdown heightened awareness of building quality, and government Recovery, Transformation and Resilience Plan funding from Next Generation EU supported rehabilitation efforts. By 2022, approvals reached 34,525 homes, a 35 percent increase from 2019. This progress is encouraging for the sector, yet it still falls short of Europe’s ambition to double rehabilitation rates by 2023, a key part of the European Regeneration Wave designed to combat extreme climate events. Spain’s annual rehabilitation rate would need to rise to about 3 percent.
Building from scratch remains more expensive. A new construction may cost around 1,000 euros per square meter, while a fully rehabilitated building tends to be substantially cheaper. On average, an apartment can cost about 15,000 euros to rehabilitate, according to Fernando Landecho, a board member of the Official College of Architects of Madrid. Rehabilitation also advances decarbonization, as the construction sector consumes large quantities of natural resources, industrial processes, and transportation. These activities account for a significant share of global greenhouse gas emissions. Susana Saiz, director of Climate and Sustainability services at Arup, points out that 40 percent of emissions come from the sector, with roughly half linked to heating and 10 percent to material production. The message is clear: substantial investment in sustainable building practices can cut emissions while preparing for efficient reuse and recycling of materials. Fernando González Cuervo, EY’s Construction and Infrastructure partner, emphasizes the opportunity to shift toward a circular use of materials and energy-efficient design.
Tradition meets technology
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For years, energy efficiency certificates have governed new builds since their approval in 2007. The construction industry has sought ways to help communities withstand heat waves and periods of heavy rain. The core strategy is to treat the environment as a central design factor, blending time-tested methods with modern innovations from project conception onward. This sustainability commitment shapes how tenders are written, with preference for environmentally friendly materials such as wood. Scandinavian nations have long demonstrated this approach, and many see potential to apply similar practices elsewhere. Other sustainable materials gaining traction include straw, bioplastics, and even CO2-reinforced concrete in some pilot programs.
One growing initiative involves integrating vegetation into building design. The soil layer provides insulation, helps absorb CO2, and offers local cooling through greenery. Experts highlight examples like the green ring around Vitoria and the planting of garden frontages, flood-prone parks, and tree-lined streets that reduce heat. Architects also call for reviving traditional ventilation methods such as cross-ventilation, while pairing them with modern LED lighting to reduce energy use. The circular economy extends to water management, with rainwater and graywater reuse in buildings where feasible. When design constraints limit landscaping, light-colored and reflective materials for sidewalks and roofs can curb urban overheating, and permeable pavements help manage humidity linked to the urban heat island effect.