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Special issue: the best papers of ENTAC 2024 • Ambiente Construído 25 • 2025 • https://doi.org/10.1590/s1678-86212025000100907 linkcopy

Open-access Climate change impacts on the thermal and energy performance of mixed-mode office buildings in a humid subtropical climate

Impactos das alterações climáticas no desempenho termoenergético de edifícios escritórios de modo misto em clima subtropical úmido

AuthorshipSCIMAGO INSTITUTIONS RANKINGS

    Abstract

    Giving the urgency of climate change, assessing building thermal and energy resilience is imperative. This paper evaluates the effects of climate change on the thermal and energy performance of a mixed-mode office building in São Paulo, considering both isolated and urban-embedded scenarios. Four scenarios were considered, derived from the Intergovernmental Panel on Climate Change (IPCC) last report, from 2022. The climate change scenarios indicate a significant increase in cooling loads for the isolated building, primarily influenced by office room’s solar orientation. Since natural ventilation tends to lose its potential to guarantee good thermal performance conditions in the future, design strategies that enhance its operation are necessary. Urban embedding, characterized by increased built density, led to higher levels of shading and lower air exchange rates, resulting in reductions in cooling loads of up to 56% compared to the isolated building. However, other unexamined factors, such as indoor air quality, daylight availability, and acoustic performance, may also influence building performance, underscoring the necessity for a holistic assessment of this complex issue.

    Keywords
    Thermal performance; Energy performance; Mixed-mode office buildings; Climate change; Urban context

    Resumo

    É fundamental considerar as alterações climáticas na avaliação da resiliência termoenergética de edificações. Este artigo analisa os efeitos das mudanças climáticas sobre o desempenho termoenergético de um edifício de escritórios com modo misto de ventilação em São Paulo, considerando cenários de um edifício isolado ou com entorno urbano construído. Quatro cenários foram considerados, baseados no 6° relatório do Painel Intergovernamental sobre mudanças climáticas (IPCC), de 2022. Observou-se um aumento na carga térmica de resfriamento nos cenários futuros, sendo a orientação solar da sala de escritórios o parâmetro de maior interferência. Para o edifício com entorno construído, maiores índices de sombreamento e menores taxas de renovação do ar foram observados nos cenários de maior adensamento urbano, causando uma redução de até 56٪ na carga térmica de resfriamento, comparado ao edifício isolado. Entretanto, outros fatores não avaliados, como qualidade do ar interior, disponibilidade de luz natural e desempenho acústico, também podem influenciar o desempenho do edifício, ressaltando a necessidade de uma avaliação holística da problemática.

    Palavras-chave
    Desempenho termoenergético; Edifício de escritórios de modo misto; Mudanças climáticas; Entorno urbano

    Introduction

    The surge in global energy consumption, fuelled by human activities and driven by rising living standards and rapid economic growth, has significantly contributed to the increase in Earth’s average temperature, particularly since the 17th century, compared to pre-industrial levels. (IPCC, 2021). Thus, a greater energy production from non-renewable sources to supply the increase in energy consumption in different sectors caused an accelerated and irreversible increase in greenhouse gas (GHG) emissions, the main cause of environmental degradation. This is pointed out as one of the main causes of global warming, which refers to changes in the patterns of the global climate system, resulting in the increase in global average temperatures and extreme weather events (IEA, 2017).

    The Climate Model Intercomparison Project Version 5 (CMIP5) of the Intergovernmental Panel on Climate Change (IPCC) Fifth Report (AR5) introduced scenarios called Representative Concentration Pathways (RCPs), identified by their total radiative forcing (warming due to GHGs in the atmosphere, expressed in W/m²) to be achieved during or near the end of the 21st century (IPCC, 2013). The main scenarios were: RCP 2.6 (mitigation scenario, very low forcing level), RCPs 4.5 and 6.0 (stabilization scenarios) and RCP 8.0 (scenario with very high GHG emissions). The latest version of the IPCC report (AR6) maintains the scaling of forecast scenarios, but in a new version, which includes net zero emissions (GHG removed from the atmosphere by vegetation), thus bringing five new emission scenarios, for the periods from 2015 to 2100, identified by Shared Socioeconomic Pathways (SSPs), namely: SSP1-1.9 (more optimistic, which considers that CO2 emissions will decline rapidly in the coming decades, reaching net zero emissions by 2050), SSP1-2.6 (reaching net zero emissions by 2080), SSP2-4.5 (intermediate scenario, in which emissions would increase in the coming years and reduce in the middle of the 21st century, but not enough to reach net zero emissions before 2100), SSP3-7.0 and SSP5-8.5 (more pessimistic scenarios, in which emissions would continue to increase in the coming decades, but at different intensities) (IPCC, 2021).

    Global warming has proven to be a critical factor in humanity’s future energy demand, with a possible increase in the frequency of summer heat waves. As a result, there will be an increase in energy demand for cooling systems in warmer climate zones (Alves; Duarte; Gonçalves, 2021; Bell et al., 2022; Berger et al., 2014; Bienvenido-Huertas et al., 2020; Casagrande; Alvarez, 2013; Gilani; O’Brien, 2021; Kolokotroni et al.,2012; Sánchez-García et al., 2019; Triana; Lamberts, Sassi, 2018). In 2021, building operations accounted for 30% of global final energy consumption and 27% of total emissions from the energy sector (8% being direct emissions from buildings and 19% indirect emissions from the production of electricity and heat used in buildings) (IEA, 2022). It is therefore imperative to improve the energy performance of buildings as a way of containing global warming (Kini; Garg; Kamath, 2017). The main source of anthropogenic GHG emissions is through energy generation (Alves; Duarte; Gonçalves, 2021), which highlights the need to evaluate the effect of urban densification on the energy performance of buildings in different climatic contexts (Salvati; Coch; Morganti, 2017).

    Urban densification, from an energy perspective, could present negative effects for outdoor and indoor spaces, since it can be one of the causes of urban heat island effects. It also interferes with direct and diffuse solar radiation, modifying solar reflectance and shading, and, consequently, with the energy consumption of buildings (Lima, 2018). Dense urban fabric impacts building performance through increased shading (Campos, 2015; Han; Taylor; Pisello, 2017). Also, restricted natural ventilation, particularly due to neighbouring buildings, can contribute to poor indoor airflow and, consequently, increased energy consumption (Izadyar et al., 2023; Martins et al., 2014). Consequently, increased urban density can compromise building thermal, lighting, and energy performance (Campos, 2015). Other Brazilian studies address the impact of different characteristics of urban morphology on the thermal performance of indoor environments (Ferreira; Assis, 2016; Gonçalves et al., 2011; Marra; Morille; Assis, 2017).

    Simultaneously to urban densification, mechanical cooling systems in buildings have experienced rapid growth, with a 4% annual increase since 2000 and a projected 3.2% rise by 2050 (IEA, 2024). This surge in demand drives electricity consumption, particularly in emerging markets and developing economies, due to increased air conditioning adoption and the intensifying need for cooling driven by climate change (IEA, 2024). An important strategy for reducing energy consumption with cooling is the use of passive strategies, such as natural ventilation, which has been widely studied in the literature as a potential energy saver in mixed-mode buildings (Salcido; Baheem, Issa, 2016). The mixed-mode ventilation system, or hybrid ventilation, consists of providing mechanical air-conditioning and natural ventilation systems in the same environment, with the operation of each system being determined according to the thermal comfort conditions of the indoor environment (Salcido; Baheem, Issa, 2016). The coupled analysis of climate change and building thermal performance has emerged as a relevant and growing research area, driven by the intensifying effects of climate change.

    Studies on the effects of climate change and urban densification on building thermal performance, particularly for mixed-mode office buildings, are limited. Investigations coupling two of these three topics (climate change, urban densification and/or mixed-mode office buildings) are more present in the literature. Gilani and O’Brien (2021) estimated the natural ventilation performance of mixed-mode office buildings under the effects of climate change, throughout the buildings’ lifetimes, considering cities with different climate conditions in the United States and Canada (ASHRAE climate zones 1 to 7 – from very hot and humid to very cold). CCWorldWeatherGen tool was used to generate future weather files for 2050 and 2080. The authors used computer simulations in EnergyPlus to show that the use of energy for cooling can be considerably reduced by incorporating natural ventilation based on window usage patterns. However, the natural ventilation performance is highly affected by outdoor conditions, especially in the future, due to climate change. Despite not explicitly comparing climate differences, the study reveals a clear trend: warmer future climates lead to diminished operable window availability and heightened thermal discomfort when relying on natural ventilation. Consequently, cooling energy consumption is projected to escalate, commonly by more than 30 kWh/m², in these regions. Sánchez-García et al. (2019) aimed to analyse energy savings and thermal comfort levels of mixed-mode office buildings for both present and future scenarios, by applying an adaptive comfort control mode. The authors monitored and simulated a case study building located in city of Seville, Spain (mild and humid winter, hot and dry summer), using CCWorldWeatherGen tool to generate future weather files for 2050 and 2080. Results showed the adaptive comfort model as a more resilient operation mode to climate change.

    Nevertheless, increased energy demand and consumption for future scenarios are also expected. Salvati, Coch and Morganti (2017) analysed the effects of urban density on the energy performance of a residential building located in the Mediterranean climate. Energy simulations were performed in EnergyPlus to compare situations with and without the urban context. Results showed that compact urban textures contributed to reduce the energy consumption, as opposed to the performance of the isolated building. Veloso and Souza (2024) investigated the impacts of climate change in the energy performance mixed-mode office buildings, considering different climatic conditions across Brazil. EnergyPlus was used to perform the energy simulations and the Future Weather Generator tool was used to generate future weather files. Results for the city of São Paulo showed that, despite its relatively low current energy consumption, a gradual increase is projected. The authors emphasize that mitigation measures are essential to stabilize HVAC consumption and maintain natural ventilation, highlighting the need for sustainable strategies to combat climate change-driven energy challenges. Duan, Omrani and Zuo (2025) analysed the impact of climate change on office buildings in Australia, considering different climatic conditions Canada (ASHRAE climate zones 1 to 7 – from very hot and humid to very cold); as well as the effectiveness of energy conservation measures. Grasshopper with Ladybug tools in Rhino were used to perform energy simulations and the Future Weather Generator tool was used to generate the future weather files for 2050 and 2080. Results revealed that in warm regions the efficacy of solar control measures were heightened under climate change. Conversely, in transitional climates strategies previously considered detrimental, such as shading, could become advantageous due to increased cooling demands.

    Computer simulations have been widely used to evaluate the thermal and energy efficiency of buildings in future climate change scenarios. As a result, several software tools focused on changing current weather files have been developed, aiming at integrating climate change forecasts into weather files. Most of these tools are based on the Morphing method, a statistical technique developed by Belcher, Hacker e Powell (2005) that combines present-day observed weather data with results from IPCC climate models (Troup; Fannon, 2016). Several tools can be used to generate future weather files. Table 1 characterizes the main differences between some of the most cited and/or recent tools. CCWorldWeatherGen, a free Microsoft Excel extension developed by the University of Southampton, was widely used until recently, despite its 2017 update freeze (Jentsch; Bahaj; James, 2017; Tootkaboni et al., 2021). WeatherShift, a commercial platform by Arup and Argos Analytic, offers summarized visualizations and full file purchase (WeatherShift, 2023). Future Weather Generator, a free and open-source tool developed by the University of Coimbra, provides multiplatform compatibility, flexible weather model integration, and the most recent numerical modeling capabilities (Rodrigues; Fernandes; Carvalho, 2023). Its most recent version (v2.3.0) includes the possibility to add the urban heat island effects.

    Given the future impacts of climate change and the current and growing stock of buildings, with average lifespan of 50 years, it is imperative that future buildings have low energy consumption. Natural ventilation is a strategy that improves thermal and energy performance, reducing dependence on mechanical air-conditioning systems. Therefore, we emphasize the importance of assessing the potential impacts of climate change on the thermal and energy performance of mixed-mode office buildings. By coupling climatological studies, we aim to enable the proposition of mitigating strategies.

    Objective

    This paper aims to evaluate the effects of climate change on the thermal and energy performance of a mixed-mode office building in São Paulo, considering both isolated and urban-embedded scenarios.

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    Table 1
    Main features of Morphing tools

    Method

    The research method was based on a case study and supported by computer simulations. The methodological procedure was unfolded in five key steps, as detailed in Figure 1. Detailed descriptions of each step are presented in the subsequent sections.

    Definition of a reference case

    Pereira and Neves (2018) conducted a field survey of 2,870 mixed-mode office buildings, built between 1995 and 2016 in the city of São Paulo, to raise envelope design general information. From the sample, 153 buildings were selected for on-site visit, to collect more detailed information that would characterize their thermal and energy performance (geometry and construction materials). This database was used to develop a reference model representing the sample (Figure 2). The envelope dimensions and thermal properties of this reference model were extracted from the average values of the continuous variables and the most frequent values of the categorical variables from the database, resulting in the data presented on Table 2. The mixed-mode operation works through cross ventilation on adjacent facades and individual split-type air-conditioning units, installed in each office room. The indoor heat gains (occupancy, electric lights, and equipment) and the occupancy schedule were established according to INMETRO (2022), as shown in Table 2.

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    Figure 1
    Flowchart of the methodological procedure
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    Figure 2
    Reference model. Floorplan (left) and 3D image (right) – unscaled images
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    Table 2
    Reference model input parameters

    Futures weather files for climate change scenarios

    A Typical Meteorological Year (TMY) weather file of the city of São Paulo (Sao.Paulo-Congonhas.AP.837800_TMYx.2007-2021) (Climate One Building, 2021) was used to represent the current weather conditions and to generate the future weather files. Situated at 23° 32’ South latitude (on the Tropic of Capricorn), 46° 38’ West longitude and 800 meters above the sea level, São Paulo falls under the Köppen-Geiger classification of humid subtropical (Cfa) (Beck et al., 2018) and the Brazilian NBR 15220-3 bioclimatic zoning classification of cold with moderate winter (2M) (ABNT, 2024), indicating a temperate climate with hot and humid summers and moderate winter.

    The Future Weather Generator tool (v1.2.1) was chosen to generate future weather files. The tool uses the updated scenarios from the 6th IPCC report (AR6) to generate weather files for the period between 2036 and 2065 (2050) and between 2066 and 2095 (2080) (IPCC, 2021). The simulated scenarios were the SSP2-4.5, since it is more likely to occur, and the SSP5-8.5, since it represents the worst-case scenario. The original TMY weather file used to generate future weather data already accounts for urban heat island effects. This is a direct consequence of the raw data being collected from a meteorological station situated within an urban zone (Congonhas airport).

    Definition of scenarios within the urban context

    Three scenarios were defined to illustrate the reference model within São Paulo’s urban context. These scenarios were based on São Paulo’s ‘Urban Transformation Structuring Axis Zone’ (Zona Eixo de Estruturação da Transformação Urbana - ZEU) guidelines, according to the laws 16,402, from 2016 (land subdivision, use and occupation) (São Paulo, 2016) and 16,050, from 2014 (São Paulo’s strategic master plan) (São Paulo, 2014). This zone was chosen since it represents regions of the city with the highest density of office buildings, based on Pereira and Neves (2018) field survey, as shown in Table 3.

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    Table 3
    São Paulos’s zoning classification and number of buildings within each one, from Pereira and Neves (2018) database – survey based on GeoSampa website (PMSP, 2023)

    Three levels of urban densification, here called low, medium and high-density scenarios, were established as representative scenarios, as illustrated in Figure 3. The three building density levels were established based on real urban examples, identified through a panoramic photographic survey. The three scenarios feature regular street grids, blocks, and lots, with increasing concentrations of tall buildings near avenues.

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    Figure 3
    Pictures of São Paulo representing different levels of urban densification (left) and low, medium and high-density scenarios (right) – unscaled images

    To set the urban configuration of the three scenarios within the urban context, block dimensions and lot shapes were surveyed using Google Earth, for the 25 buildings within the ZEU zone (Table 3). This revealed that 14 buildings (56%) were located in blocks measuring approximately 100 m to 120 m. Consequently, these dimensions were used to set the urban context scenarios, featuring 12 lots of 1,000 m²: eight measuring 20 m x 50 m (lot A) and four measuring 25 m x 40 m (lot B) (Figure 4). Aligned with land subdivision parameters from São Paulo law 16,402 (São Paulo, 2016), local roads were set at 7 m wide and public pavements at 2.5 m wide. Table 4 displays the average usage coefficient (Coeficiente de Aproveitamento - CA) and the density of the roof projection area (Densidade de Projeção da Cobertura - DPC) for each proposed scenario.

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    Figure 4
    Blocks and lots defined for the scenarios within the urban context – unscaled image
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    Table 4
    Coefficient of use and density of the roof projection area for each adopted construction density scenario

    To define the low, medium, and high-density scenarios, buildings were designed to occupy the maximum lot dimensions, adhering to occupation parameters specified in São Paulo law 16,402 (São Paulo, 2016) and the city’s building code (PMSP, 2017). While these regulations may evolve with time, the scenarios represent consolidated urban areas, less susceptible to legislative changes. Nevertheless, this reliance on current legislation constitutes a study limitation. Scenario configurations were developed using three dimensioning procedures, resulting in four building volumes, as follows:

    1. 1st procedure: minimum setbacks were applied to both lot typologies, and the maximum usage coefficient was divided by the resulting lot area, yielding a maximum building height of six floors;

    2. 2nd procedure: the maximum usage coefficient was divided by the reference model’s floor area, resulting in a maximum building height of 16 floors; and

    3. 3rd procedure: buildings on both lot sizes were extended to the rear setback limit, resulting in nine-story buildings for the 20 m x 50 m lots and twelve-story buildings for the 25 m x 40 m lots.

    One and two-story buildings were incorporated into the scenarios to introduce urban density variability and reflect diverse real-world urban configurations.

    Thermal and energy performance simulations

    EnergyPlus v 9.6 was used to develop the thermal and energy performance simulations, and Euclid v 0.9.3 plugin was used to model the building geometry. Natural ventilation was performed using the Airflow Network group, which performs pressure, air flow, temperature and humidity calculations, as well as sensible and latent heat exchange calculations (EnergyPlus, 2016). The wind pressure coefficients (Cp) of the reference model’s openings were calculated considering the isolated building (without surroundings) and the building within the urban context (low, medium and high-density scenarios). Computer fluid dynamics (CFD) simulations were performed using the cloud-based online CpSimulator tool, which uses OpenFOAM to solve steady-state Reynolds-Averaged Navier-Stokes (RANS) equations, employing turbulence models tailored for specific atmospheric boundary layer (ABL) applications (Bre; Gimenez, 2022). CpSimulator processes geometry data from EnergyPlus input data files, creating a regular polygonal computational domain with sizes based on best practice guidelines (Bre; Gimenez, 2022).

    The fine mesh configuration was chosen for this work, which is also the default configuration on the CpSimulator platform. Also, the atmospheric boundary layer (ABL) was configured as urban terrain type. The mixed-mode control was structured using EnergyPlus’ Energy Management System (EMS) function, considering the indoor operative temperature thresholds set by ASHRAE 55 adaptive comfort model (ASHRAE, 2023), 80% acceptability. The mixed-mode system is programmed to operate as follows: when the thermal zone is occupied and the indoor operative temperature is outside the comfort limits, the windows are closed and the air-conditioning system is turned on; when the thermal zone is occupied and the indoor operative temperature is within the comfort limits, the air-conditioning is turned off and the windows are opened; when the thermal zone is unoccupied, the windows are closed and the air-conditioning system is turned off.

    The simulations were developed in two phases: the first one considering the isolated reference model, with two solar orientations - North-South and East-West; the second one considering the reference model within the building context (low, medium and high-density scenarios), for the North-South solar orientation. Both stages were simulated for the current and future scenarios, resulting in a total of twenty-five scenarios, as explained in Figure 5.

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    Figure 5
    Simulated scenarios

    Results analysis

    Hourly annual simulations were carried out, considering the current and future weather files of the city of São Paulo. The office rooms that presented the highest and lowest cooling loads for the current weather file scenario were selected for the results analysis, which consists of the one facing North and East facades (leeward, 62 kWh/m².year of cooling loads for the 5th floor and North-South axis orientation) and the one facing South and East facades (windward, 24 kWh/m².year of cooling loads for the 5th floor and North-South axis orientation) (Figure 6). The analysis included floors 1, 3, 5, 7, and 9. Results were analysed based on the following performance indicators: air exchange rate per hour (ACH), ratio of annual air-conditioning operating hours to annual occupied hours (%), and cooling loads (kWh/m². year). The heating loads were disregarded from the analysis due to its irrelevant results. Considering the building’s mixed-mode operation, cooling loads were adopted as a representative metric for evaluating both thermal and energy performance. A reduction in these loads directly correlates with improved indoor thermal performance, specifically by increasing the time occupants experience conditions within the established thermal comfort zone.

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    Figure 6
    Building’s North-South solar orientation (left); and East-West solar orientation (right), highlighting the analysed office rooms – unscaled images

    Results and discussion

    Analysis of future weather files

    The TMY weather file of São Paulo, developed using data from 2007 to 2021, indicates an annual mean air temperature of approximately 20 °C. Monthly averages of maximum and minimum air temperatures are observed between 17 °C and 25.5 °C, with a mean relative humidity maintained at approximately 70%. Seasonal variations in wind direction are evident; however, a prevailing wind direction from the South and South-Southeast is noted, particularly during the winter period.

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    Figure 7
    Monthly mean - dry bulb temperature

    Climate change manifests itself in many ways, with one of the most obvious effects being the increase in global temperatures. Weather data on dry bulb temperature and relative humidity were extracted from the current and future weather files (SSP2-4.5 and SSP5-8.5) to analyse changes over time and according to different climate projections. The mean dry bulb temperatures for the SSP2-4.5 scenario shows an increase of 1.2 °C by 2050 and 2 °C by 2080. As for the SSP5-8.5 scenario, the increase is 1.6 °C by 2050 and 2.9 °C by 2080 (Figure 7). The mean relative humidity shows a decrease in the future scenarios. The current average of 70% drops to 66% in average, for both climate projections and for both time frames (Figure 8). Despite projections of global warming occurring under relatively constant humidity, the most recent IPCC report provides limited clarity on the extent and causes of observed humidity changes within the troposphere (Douville et al., 2022). Moreover, while the AR6 provides a broad understanding of the expected trends in near-surface relative humidity, the uncertainties highlighted suggest that projections should be interpreted with caution (IPCC, 2021). The variability in model outputs and the discrepancies with observed data underscore the need for continued research and refinement in climate modelling to enhance the reliability of future relative humidity projections.

    Thermal discomfort is a function of, among other variables, dry bulb temperature and relative humidity. Projected temperature increases under climate change scenarios SSP2-4.5 and SSP5-8.5 are anticipated to elevate the sensation of heat discomfort for building occupants. This will result in increased cooling energy requirements to maintain thermal comfort. Therefore, detailed simulation analyses to understand possible impacts of future climate change are imperative.

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    Figure 8
    Monthly mean - relative humidity

    Effects of climate change on the isolated building

    Figures 9 and 10 show variations in the cooling loads and annual air-conditioning operating hours for building’s solar orientations of 0° (N-S) and 90° (E-W). Under the IPCC’s intermediate (SSP2-4.5) and pessimistic (SSP5-8.5) climate change scenarios, simulations indicate a substantial rise in cooling loads and in annual air-conditioning operating hours by 2050 and 2080, relative to current conditions. Such increases occur regardless of the building’s solar orientation. Building orientation significantly impacted results, with the 90° (E-W) orientation exhibiting higher cooling loads and annual air-conditioning operating hours. The south and east-facing office room, being windward and receiving direct solar radiation only from the east, exhibited better thermal and energy performance compared to the north and east-facing room, which is leeward and exposed to direct solar radiation from both facades. These findings align with studies by Bamdad et al. (2022), Serasinghe, Wijewardane and Nissanka (2022), and Farahani et al. (2022), which also reported increased cooling energy demand under future climate change scenarios across various global regions, including hot and cold climates. They are also consistent with Gilani and O’Brien (2021), who projected an energy consumption increase exceeding 30 kWh/m² for mixed-mode office buildings in hot climates (ASHRAE climate zone 1).

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    Figure 9
    Cooling heat load (bar) and proportion of annual air conditioning operating hours to annual occupied hours (diamond) for North-South building solar orientations
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    Figure 10
    Cooling heat load (bar) and proportion of annual air conditioning operating hours (diamond) to annual occupied hours for East-West building solar orientations

    The floor number significantly influenced results, with higher floors experiencing greater wind speeds, which led to improved thermal performance through enhanced natural ventilation, reducing air-conditioning operating hours and cooling loads. Given the reference model’s mixed-mode ventilation operation, natural ventilation was assessed based on air exchange rates during natural ventilation periods (Figure 11). The building’s solar orientation had little influence on air change rates (differences around -3% to 3% between both), which can be attributed to the room’s cross ventilation on adjacent facades, which ensures that, for most wind directions, at least one window is windward. As the predominant wind direction in São Paulo is South/South-Southeast (S/SSE), the South-East offices had a slightly higher air exchange rate. Air exchange rates show very little differences between the SSP2-4.5 and SSP5-8.5 scenarios, therefore only the SSP2-4.5 scenario was presented. It is worth highlighting that, on higher floors, elevated indoor air speed can impede the use of cross ventilation, as occupants may close windows to avoid discomfort from strong drafts.

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    Figure 11
    Air change rates for climate change scenario SSP2-4.5

    Effects of climate change on the urban embedded building

    Figure 12 illustrates the cooling loads and annual air-conditioning operating hours for the North-East and South-East facing office rooms on the 5th floor (the reference model’s middle floor) of the North-South oriented building. Increased built-environment density leads to greater shading on the reference building, directly reducing its cooling loads.

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    Figure 12
    Cooling loads and annual air-conditioning operating hours of the North-East and South-Eastfacing office rooms, building’s solar orientation North-South, middle floor (5th) – isolated building and low, medium and high-density scenarios

    Only 30% of the scenarios within the urban context resulted in higher cooling loads, if compared to the isolated building scenario, as shown in Table 5 (analysis considering the 5th floor only). The high-density scenario showed cooling loads reduction for all weather files and for both office rooms (North-East and South-East), with a maximum demand decrease of 56% (North-East facing office room, SSP2-4.5 weather file for 2080).

    For the future weather files, both IPCC climate change scenarios (SSP2-4.5 and SSP5-8.5) resulted on cooling loads increase, if compared to the current weather file scenario (Table 6). However, the increase was less pronounced in scenarios with higher urban density, indicating that the shading effects of the surrounding built environment contributed towards reducing the office rooms cooling loads. Among the analysed climate change scenarios, the SSP2-4.5 (2080) exhibited the lowest percentage increase compared to the current scenario. Consistent with Han, Taylor and Pisello (2017) and Salvati, Coch, and Morganti (2017), these findings confirm that shading from nearby obstructions reduces energy consumption by lowering cooling loads. It is worth highlighting, however, that this analysis focused solely on results from the 5th floor and did not account for heating loads, which are minor during the day given the climate and location.

    Figure 13 illustrates the air exchange rates during natural ventilation periods of the South-East facing office room on the 5th floor (the reference model’s middle floor) of the North-South oriented building. A higher density of the built environment correlates with lower air exchange rates. This is primarily due to the formation of wind shadow zones on building facades, which reduces wind pressure and, therefore, inhibits cross ventilation. In fact, this can be confirmed by the wind pressure coefficients (Cp) of the South and East facade openings (Figure 14). Increased built density, especially in the medium and high-density scenarios, leads to negative wind pressure coefficients, impairing cross-ventilation in office rooms. Lower floors are also affected in the low-density scenario.

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    Figure 13
    Air exchange rates of the South-East facing office room, 5th floor, building’s solar orientation North-South
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    Figure 14
    Wind pressure coefficients for the office room located on the South-East (windward) facade
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    Table 5
    Percentage reduction in cooling loads of the scenarios within the urban context compared to the isolated building - building’s solar orientation North-South, middle floor (5th)
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    Table 6
    Percentage increase in cooling loads of the scenarios within the urban context compared to the isolated building - building’s solar orientation North-South, middle floor (5th), future weather files (in comparison to the current weather file)

    Conclusions

    This work evaluated the effects of climate change on the thermal and energy performance of a mixed-mode office building located in São Paulo, considering both isolated and urban-embedded building configurations. Four future weather files were used to simulate scenarios for the period between 2036 and 2065 (2050) and between 2066 and 2095 (2080), considering the IPCC SSP2-4.5 and the SSP5-8.5 climate change scenarios. The office rooms facing North and East facades (leeward) and facing South and East facades (windward) of the 1st, 3rd, 5th, 7th and 9th floors were included in the results analysis.

    The analysis indicates that future scenarios (2050 and 2080) will lead to a significant increase in cooling loads, ranging from approximately 74% (SSP2-4.5, 2050) to 218% (SSP5-8.5, 2080) increase for the isolated building scenario. Consequently, air-conditioning usage is projected to increase by 44% to 127% for the isolated reference model, depending on the specific future scenario. The results were influenced by several factors, including building orientation, office room orientation, and floor height. Given the study’s limited scope regarding urban scenarios and solar orientations, office room orientation had the most significant impact, while building orientation had the least. This underscores the importance of analysing office rooms individually rather than using building-wide averages.

    Three levels of urban densification – low, medium, and high-density scenarios – were established to analyse urban-embedded building configurations. Increased built-environment density leads to greater shading, directly reducing the building cooling loads. Nevertheless, a higher density of the built environment also contributes to lower air exchange rates, as a result of diminished wind pressure on building facades, and subsequent reduction in cross-ventilation. The urban-embedded building showed reductions in cooling loads of up to 56% compared to the isolated building, for the current weather file scenario. As to the climate change scenarios, a less pronounced increase in cooling loads was observed for future climate scenarios in higher-density urban contexts. While the percentage increase in cooling loads of future climate change scenarios varied between 80% (North-East office room, SSP2-4.5, 2050) and 199% (South-East office room, SSP5-8.5, 2080) for the isolated building, it varied between 72% (North-East office room, SSP2-4.5, 2050) and 181% (South-East office room, SSP5-8.5, 2080) for the high-density urban embedded building.

    This study reveals that high-density urban configurations can contribute to reduced cooling load demands in mixed-mode office buildings by limiting solar radiation through increased sky obstruction. However, further research is needed to validate these results under different input conditions. Moreover, it is essential to acknowledge that unexamined factors, such as indoor air quality, daylight availability, and acoustic performance, may significantly influence overall building performance, highlighting the necessity for a holistic assessment of this complex issue. Furthermore, substantial research remains to be conducted regarding natural ventilation, energy consumption (heating and cooling), urban densification, room and floor patterns, and building geometry.

    Considering a building’s lifespan of between 50 and 75 years, current buildings must maintain good performance in the face of climate change. It is therefore important to encourage the use of strategies to improve thermal and energy performance, such as the mixed-mode ventilation, reducing the sole dependence on air-conditioning systems. However, as natural ventilation tends to lose its potential to guarantee good thermal performance conditions in the future, due to global warming, design strategies that enhance its operation are necessary. From this perspective, this study contributes to this discussion, aiming to foster this topic and stimulate further research on urban strategies, technologies, and guidelines.

    This study acknowledges several limitations. Firstly, besides Future Weather Generator being, currently, the most up to date integrated tool for generating future weather files based on IPCC AR6 scenarios, alternative programming language packages for this purpose were not investigated. Secondly, although the individual analysis of office rooms provided valuable insights into orientation-dependent thermal and energy performance, it precluded the generation of whole-building performance data and potential compensatory effects. Lastly, while major urban and building changes due to legislative shifts are deemed less probable within the 75-year timeframe for consolidated urban areas such as the one here explored, this assumption may not hold true for all urban contexts.

    Acknowledgments

    This research was supported by the Coordination for the Improvement of Higher Education Personnel – Brazil (CAPES) – Financing code 001.

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    Edited by

    • Editor:
      Enedir Ghisi
    • Editora de seção:
      Luciani Somensi Lorenzi

    Publication Dates

    • Publication in this collection
      16 June 2025
    • Date of issue
      2025

    History

    • Received
      31 Jan 2025
    • Accepted
      18 Apr 2025
    Creative Common - by 4.0
    This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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