For centuries, our homes were built to protect us from the cold. Today, they face a problem they were never designed to solve. Global warming is advancing faster than our buildings can adapt. Houses that once excelled at keeping heat inside are now discovering the opposite challenge: they struggle to let it out.
Why does a cave remain cool in summer and warm in winter without consuming energy? The answer lies not in technology, but in physics. For centuries, vernacular architecture used thermal mass, humidity and natural materials to create homes that worked with the climate rather than against it. In the middle of the climate crisis, those ancient solutions are attracting renewed scientific attention.
Spain has long learned to live with summer. Shutters, courtyards, shade and cross ventilation are part of its architectural culture. Yet even here, an increasing share of the building stock relies on air conditioning to provide acceptable indoor comfort. Meanwhile, cities once defined by long, cold winters are discovering that their homes retain heat far better than they can release it.
The building sector faces a double challenge: decarbonising while adapting to a warmer world. These goals should reinforce one another, but they do not always do so. For decades, we have focused on keeping heat in to reduce energy demand. This century, we must learn how to let it go.
A low-energy building is not necessarily a healthy one.
Decarbonisation cannot simply mean making buildings more airtight and wrapping them in layers of synthetic materials. If we improve energy performance while neglecting indoor environmental quality, we risk solving one problem by creating another. A home does more than consume energy. It shapes the air we breathe, the humidity we feel, our exposure to indoor pollutants, the quality of our sleep, our thermal comfort and, ultimately, our health and well-being.
This is why bio-based materials are attracting growing attention. Earth. Timber. Straw. Hemp. Cellulose. Rice husks. Lime renders. Many of these materials store biogenic carbon, have a lower environmental footprint throughout their life cycle and fit naturally within a circular economy. Their hygroscopic properties also allow them to absorb and release moisture, helping to create healthier and more stable indoor environments.
Perhaps the architecture of the future will not come from inventing entirely new materials, but from understanding why vernacular buildings (and many historic structures built with stone, earth, timber, lime or ceramic) have endured for centuries. Science now allows us to explain what traditional builders understood through experience.
The homes of the future should not only consume less energy. They should also become climate shelters: places that protect both human health and the health of the planet.
Beatriz Velasco is an architect, lecturer at the European University of Valencia, and a PhD researcher at the School of Architecture of Barcelona (ETSAB), Universitat Politècnica de Catalunya (UPC). Her work focuses on healthy housing, indoor environmental quality and the use of bio-based materials to promote healthier, more sustainable and climate-resilient buildings.