Abstract
Climate change has become one of the most important global challenges that requires international collaboration to deal with. According to IPCC(IPCC, 2023), global warming (GW) has already reached 1.1⁰C in 2011-2020 as compared to the pre-industry level, and by 2050, it is likely to reach 1.5 ⁰C given a very low greenhouse gas (GHG) emission scenario (Shared Socioeconomic Pathways, SSP1-1.9), whereas it is more likely to reach 2⁰C with moderate mitigation efforts (SSP2-4.5) which is considered the current pathway. Impacts of the climate change on settlements and human health are already visible including heatwaves, droughts, extreme precipitation, floods, storms, and increased heat-related human mortality and morbidity rates caused by increased frequency and intensity of extreme climate events. Considering the high levels of CO2 emissions, energy use and urbanization with other drivers of vulnerability, the adverse impacts on well-being of people and projected risks on cities and urban aeras are expected to increase in the future (Chaudhry, 2024; Das et al., 2024; Jurgilevich et al., 2023). Rising temperatures and more frequent heavy precipitation events have already been increasing the environmental loads on buildings, and these loads are expected to intensify further in the future, exacerbating the risks to indoor overheating and moisture-related deterioration on buildings, as well, bring greater challenge of energy conservation (Athauda et al., 2023; Duan et al., 2025; Y. Lin et al., 2023; Waddicor et al., 2016). It is well known that Greenhouse Gas (GHG) emission is the primary driver of climate change. Buildings are responsible for 31% of global CO2 emissions (95% GHG emissions from buildings are CO2 emissions) with 50% arising from energy use in residential buildings, 32% from energy use in non-residential buildings, and the remaining 18% from embodied emissions (Cabeza et al., 2022). Global CO₂ emissions from the building sector rose substantially between 1990 and 2019, driven not only by rising energy consumption of existing buildings but also by the rapid expansion of urban areas. Although in some countries, such as those in Northern America and Europe, the rate of urbanization has been stabilized in the past 30 years, the total energy use of existing buildings has continued to increase because of the growing use of household appliance, higher indoor quality standards as well as limited depth of retrofit (Berardi, 2017; González-Torres et al., 2022; Santamouris & Vasilakopoulou, 2021). In other countries, such as those in Eastern Asia and South America, the urbanization rate climbed steeply over the past three decades. In Eastern Asia, the urban expansion has been a major driver of rising energy consumption and CO₂ emissions in the building sector(Anwar et al., 2020; D. Li et al., 2024; X. Wang et al., 2012); in South America, building energy demand has grown with urban expansion, due to the increase of energy-using appliances, expanded floor space per capita. The increased demand of buildings and energy use has not been accompanied by efficient building design, given the countries in this region have not widely adopt unified and mandatory building energy codes (Asturias-Schaub & Gil-Alana, 2023; The World Bank, 2024; Van der Borght & Pallares Barbera, 2023). CIB W040 – Heat and Moisture Transfer in Buildings Page | 1 Over the next three decades, many countries have committed to achieve net-zero carbon emissions by 2050 in line with the Paris Agreement and the goal of limiting global temperature rise to 1.5 °C above pre-industrial levels. Achieving this target is highly challenging, particularly under conditions of changing climate, intensified climate loads, and higher indoor environment quality expectations(IEA, 2024; Kutty et al., 2023; Liyanage et al., 2024a; Tajuddeen & Sajjadian, 2024). The challenge is even greater for the regions that are still anticipated to experience urban expansion in the next 30 years, such as Eastern Asia, South Asia, Africa and Latin America (IEA, 2023; United Nations Environment Programme, 2025). For countries where urbanization has stabilized—mainly in Europe, North America, Oceania and some developed countries in Asia—the energy retrofit of existing buildings is the most important strategy for achieving the goal of decarbonization. Retrofitting efforts must not only improve energy efficiency and reduce operational emissions, but also ensure indoor thermal comfort and prevent moisture-related deterioration or unintended hygrothermal side effects (Alazazmeh & Asif, 2021; Hilbrecht et al., 2025; Recart & Sturts Dossick, 2022; Schroderus et al., 2025). On the other hand, in regions with continuing urban expansion, decarbonization ought to consider combining energy-efficient retrofits with low-carbon urban planning and design—including passive design strategies, green infrastructure, and resilient urban landscapes—to ensure that both existing and newly built environments are sustainable, comfortable, and climate-adaptive, minimizing additional emissions (Liddo et al., 2025; Santamouris, 2014a; Seidu et al., 2025; UN HABITAT, 2022).