During the sweltering summers of recent years, many Britons have found their homes unbearable, designed as they are for the country’s typically cool weather. In 2020, the heatwave was so severe that approximately 2,000 people died in England, most in their own homes. But this is more than just a Northern Hemisphere problem. In Brazil, buildings and houses also struggle to cope with rising temperatures and the more intense, prolonged heatwaves predicted as global warming escalates.
A rare Brazilian study in this field analyzed 92 properties in Florianópolis, Santa Catarina, examining energy consumption in 2010 and projecting conditions for 2050 and 2090. Among the properties, 39% were stores, 31% offices, 21% restaurants, and 9% residences. The study, published in Sustainable Cities and Society in July, found that by 2050, 37% of these buildings could overheat, reaching temperatures uncomfortable for occupants. This is largely due to construction methods that retain, rather than dispel, heat.
Ironically, the sleek, high-end buildings in central Florianópolis were the least prepared, with sealed windows and heat-absorbing dark exteriors, the researchers noted. In São Paulo, similar design flaws are widespread, especially in commercial buildings like those in the upscale Itaim district.
“Sealed glass-front buildings are completely at odds with the realities of climate change,” says Denise Duarte, an engineer at the University of São Paulo’s School of Architecture and Urban Planning (FAU-USP). Her research, with funding from FAPESP, explores ways to make buildings more resilient to climate change.
A 2021 study by her team, published in Energy and Buildings, analyzed São Paulo buildings constructed in the 2000s. The analysis predicted that by 2074, total hours of thermal comfort in these structures could drop from 81% to 65% due to higher temperatures.
“I’ve noticed a growing trend of new residential buildings with façades in graphite, petroleum blue, or even black—colors that absorb much more heat,” Duarte remarks. “While they don’t have to be white, opting for lighter shades can significantly reduce heat absorption.”
“Buildings with highly transparent, clear glass windows are especially prone to overheating, particularly if they lack shading,” adds Roberto Lamberts, an engineer at the Federal University of Santa Catarina (UFSC) and coauthor of the study in Sustainable Cities and Society. “We’re still using design and construction standards suited for a milder climate—one that no longer exists. The coming years will be far hotter than today.” Shading is a useful strategy for shielding buildings from intense sunlight during peak heat. This can involve architectural features such as sunshades, balconies, or extended eaves.
In collaboration with researchers from the University of California, Berkeley, the UFSC team explored solutions that reduce dependency on air conditioning. Their recommendations include applying reflective coatings and paints to roofs and slabs to minimize heat absorption, and installing solar control glass to prevent interiors from overheating (see infographic below).
Cool roofs—featuring light-colored, reflective surfaces with high thermal emissivity (the ability to release absorbed heat)—are an effective and affordable solution.
“Construction methods need to be adapted to reduce reliance on air conditioning wherever feasible,” says Duarte. The UFSC study predicts that energy demand for cooling will rise by 48% by 2050. Today, air conditioning already contributes 3% of global carbon emissions. Passive thermal control systems, such as shading façades and roofs, as well as natural ventilation—including at night—should play a bigger role, the researchers suggest.
“The widespread use of air conditioning may worsen the urban heat island effect by increasing outdoor temperatures in non-cooled areas,” says engineer Alberto Hernandez Neto from the Polytechnic School (Poli) at USP, who was not involved in Lamberts’s study (see Pesquisa FAPESP issue n° 331).
Given the impracticality of eliminating air conditioning altogether, researchers are instead focusing on making it more sustainable. For instance, a study published in March in the Brazilian Journal of Technology by researchers from the Federal Institutes of Rondônia and Amazonas found that better control of outdoor air intake and fine-tuning indoor temperature settings could significantly reduce energy consumption.
A building in Belo Horizonte with a green roof: a practical solution for lowering indoor temperaturesRicardo Funari / Brazil Photos / Lightrocket via Getty Images
Progress amid challenges
Architects and engineers have made efforts to promote adaptive building methods, but success has been uneven. In 2023, Lamberts and his team helped to establish thermal resilience requirements for the lowest-cost housing (Tier 1) in the Brazilian Government’s Minha Casa, Minha Vida program, codified in Ordinance No. 725 of June 15, 2023.
The UFSC team defined thermal transmittance parameters—a measure of building thermal efficiency—and recommended strategies such as light-colored roofs, minimum window opening sizes, and adequate shading. “Even though this was only applied to Tier 1, it was a significant step forward,” Lamberts explains. “We achieved an 84% reduction in thermal loads in Palmas (Tocantins), 92% in Fortaleza (Ceará), and an average reduction of over 50% in Brazil’s hottest regions.”
Duarte also played a role in crafting São Paulo’s 2050 Climate Action Plan through the FAPESP-funded Biota Synthesis program. While the initiative mainly targets rural areas, one research group demonstrated that forest restoration could help cool nearby urban zones. However, securing buy-in for these ideas from private real estate developers has been more challenging. “There’s still a certain level of climate skepticism, and many firms are content to meet only the minimum resilience criteria,” Lamberts notes.
Duarte and Lamberts had the opportunity to discuss these issues during the 50th National Convention of the Association of Architecture Firms (AsBEA), held in Florianópolis from June 19 to 22. On June 20, media outlets reported the tragic deaths of over 1,000 people during a pilgrimage to Mecca, Saudi Arabia, caused by overcrowding and heat-related discomfort. “While events like these do draw public attention, we’re still a long way from achieving meaningful change,” says Lamberts.
Hernandez Neto, from Poli-USP, points to signs of progress: “in cities like São Paulo and Rio de Janeiro, sustainable building projects are incorporating features like green roofs, ventilated façades, and shading systems to reduce thermal load and improve energy efficiency.”
At Poli-USP, researchers run courses and lectures for architects and builders to promote sustainable construction and thermal resilience practices, including passive solar energy and natural ventilation strategies. Participants often visit the Sustainable Construction Innovation Center (CICS), where alternatives to reduce greenhouse gas emissions and improve thermal performance are being developed (see Pesquisa FAPESP issue n° 278). “It is important that we continue to explore and adopt more sustainable solutions,” says Hernandez Neto.
The story above was published with the title “Keeping heat in check” in issue 345 of November/2024.
Project
The role of planning, urban design, and building design in adapting to climate change at the microscale: Contributions to an interdisciplinary approach (n° 16/02825-5); Grant Mechanism FAPESP Research Program on Global Climate Change ; Principal Investigator Denise Helena Silva Duarte (USP); Investment R$115,059.12.
Scientific articles
KRELLING, A. F. et al. Defining weather scenarios for simulation-based assessment of thermal resilience of buildings under current and future climates: A case study in Brazil. Sustainable Cities and Society. Vol. 107, 105460. July 15, 2024.
ALVES, C. A. et al. The recent residential apartment buildings’ thermal performance under the combined effect of the global and the local warming. Energy and Buildings. Vol. 238, no. 1. 110828. May 2021.
NEVES, M. V. L. et al. Automação predial: Um estudo sobre economicidade no uso de aparelhos de ar-condicionado. Brazilian Journal of Technology. Vol. 7, no. 1. Mar. 26, 2024.
