Formaldehyde (HCHO) is a toxic compound of concern in indoor environments (Jung and Awad 2021a; Awad and Jung 2021). The sources of HCHO found in rooms are highly varied, and this compound, typically released from building materials and furniture, continues to be emitted over extended periods due to material characteristics (Jung and Al Qassimi, 2022; Jung and Awad, 2021b). Accordingly, it is necessary to investigate the factors influencing indoor HCHO generation and identify effective control measures (Dubai Municipality, 2024, pp. 6–7; Jung et al., 2021c).

Dubai Municipality has established specific guidelines for indoor air quality to promote healthier living environments (Arar et al., 2022). These guidelines, known as HSD GU119“Technical Guidelines for Indoor Air Quality (IAQ) for Healthy Life,” were released in January 2023 (Arar and Jung 2022; Dubai Municipality, 2024). According to a Dubai Healthcare City report, 15% of Dubai residents have experienced symptoms of Sick Building Syndrome (SBS) caused by various indoor and outdoor air pollutants (Najini et al., 2020; Jung and Awad, 2023). In response, the Dubai Municipality initiated IAQ concentration standards (Dubai Municipality, 2022, p. 32). These standards specify that new houses, before occupancy, must have less than 0.08 ppm (parts per million) of HCHO, less than 300 μg/m³ of Total Volatile Organic Compound (TVOC), and less than 150 μg/m³ of Particulate Matter less than 10 microns (PM₁₀) after 8 h of continuous monitoring (Dubai Municipality, 2024, pp. 31–33). These regulatory efforts align with broader strategies for pollutant mitigation in dense urban housing, as outlined by Jung and Abdelaziz Mahmoud (2023), who emphasize the role of ventilation design in maintaining healthy IAQ in Dubai’s high-rise residences.

Previous studies have shown that HCHO emissions are influenced by environmental factors, including temperature and humidity (Mushtaha and Helmy, 2017; Liang et al., 2016a). This aligns with previous research, which has also emphasized the broader role of material emissions, ventilation strategies, and microclimatic conditions in shaping indoor air quality (Batterman et al., 2017; Hussien et al., 2023b; Tagliabue et al., 2021; Yang et al., 2020). However, explaining the mechanism behind the impact of microclimate factors on the behavior of building materials used in Dubai houses remains a methodological challenge (Maghrabie et al., 2021). This is primarily due to the use of diverse building materials with varying compositions, types, and histories in real houses, as well as the implementation of various construction methods for each material (Kaunelienė et al., 2016).

While temperature and humidity control in indoor environments are fundamental measures to reduce HCHO generation, the influence of these factors on HCHO levels in Dubai houses has not been sufficiently documented (Jung and El Samanoudy, 2023; Al Qassimi and Jung, 2022). In particular, understanding the characteristics of HCHO generation based on actual indoor temperature control practices in Dubai residences control practices can be an effective means of proposing control strategies in indoor environments, such as houses (Mushtaha et al., 2021).

Dubai experiences extremely hot, long, windy, and humid summers, with an average high temperature of around 40 °C and overnight lows of around 30 °C in August, the hottest month. The region generally experiences sunny days every year (Jung et al., 2022a). Winters are relatively mild, with an average high of 24 °C and overnight lows of 14 °C in January, the coolest month (Jung et al., 2021a).

Due to the widespread use of air conditioning, actual indoor temperature and humidity control are often highly restricted (Jung et al., 2022e). Previous studies have produced inconsistent results regarding the relationship between temperature, humidity, and the generation of chemicals in residential spaces (Awad et al., 2022). This inconsistency can be attributed to reporting results in different situations and under varying conditions (Jung et al., 2022b). Therefore, it is necessary to systematically discuss these results to address the diversity of experiments, investigations, and analysis methods (Jung et al., 2021b). Consequently, this study aims to propose a plan for controlling HCHO in residential indoor environments by analyzing the dependencies of HCHO emissions on temperature and humidity under actual indoor temperature control practices in Dubai residences. The research adopts a dual approach: single-point measurements conducted in 50 newly constructed houses and continuous monitoring in three representative houses. This combined design provides both broad cross-sectional insights and in-depth temporal analysis, enabling a more comprehensive understanding of emission behaviors. By linking emission patterns with actual residential management practices, the study contributes to the development of adaptive, context-specific strategies for mitigating indoor HCHO pollution in hot-climate housing.

Hazardous substances are predicted to volatilize within building materials in high-temperature environments, resulting in an increased generation of indoor pollutants (Wang et al., 2021). This prediction is based on the general theory that the vapor pressure of chemicals rises with higher temperatures and absolute humidity, leading to volatilization (Wen et al., 2018). A study conducted by Śmiełowska et al. (2017) revealed that the release of chemical substances indoors is influenced by both environmental characteristics and the properties of building materials (Śmiełowska et al., 2017). The previous research by Khoshnava et al. (2020) emphasized that building materials are the primary source of harmful chemical emissions in indoor environments (Khoshnava et al., 2020). Additionally, Farzanian et al. (2016) reported that the release of chemical substances from building materials is associated with their internal composition and that the material properties contribute to variations in release intensity (Dabous et al., 2022). In other words, the content within the material determines the volatilization of chemical substances, which further varies due to the distinct characteristics of each material (Celeiro et al., 2018).

The emission of chemicals from indoor building materials is influenced by microclimate factors, including temperature, humidity, and ventilation (Hermawan and Švajlenka, 2022). These environmental conditions may lead to differences in HCHO emission, particularly in response to indoor temperature control practices (Salthammer, 2019). In Dubai, indoor air conditioning is maintained consistently throughout the year due to seasonal characteristics (D'Agostino et al., 2020). However, adjustments like natural ventilation are commonly employed during winter to regulate indoor environmental conditions (Monge-Barrio et al., 2022). Therefore, it is necessary to effectively examine the relationship between indoor temperature control practices and the emission characteristics of hazardous chemicals in residential buildings to manage IAQ (Hussien et al., 2023a; Patino and Siegel, 2018).

Notably, previous studies addressing the dependence of chemical emissions on indoor temperature and humidity conditions for residential buildings often adopted methodologies involving multiple houses measured at a single point within each house (Coggins et al., 2022; Földváry et al., 2017; Langer et al., 2016). However, these studies do not consistently report a conclusive relationship between chemical release, temperature, and humidity (Mie et al., 2017; Liang et al., 2016b). This inconsistency is likely due to variations in measurement and environmental conditions as well as differences in management history (Zhang et al., 2019; Kaunelienė et al., 2016).

Candanedo et al. (2017) examined how temperature and humidity dependencies differ when analyzed at the whole-house scale versus at the level of individual houses. It is preferable to analyze individual houses rather than all houses, as each house has distinct housing specifications and management histories (Jung et al., 2022c). Furthermore, the study aims to compare temperature–humidity dependence trends using both single-point measurements in multiple houses and continuous measurements within the same house. This dual approach provides insights that support the development of effective control strategies to suppress the release of hazardous chemicals indoors.

This study presents several key contributions to the understanding and mitigation of indoor air pollutants in social housing, particularly within the context of the Arabian Gulf. First, it analyzes HCHO emission behaviors under actual residential temperature and humidity control conditions, capturing the influence of actual residential temperature management—autonomous and artificial—rather than relying on controlled laboratory simulations. Second, it employs a comparative measurement methodology, combining single-point and multi-day continuous measurements across 50 newly constructed houses to reveal temporal dynamics and spatial variability in pollutant emissions. Third, the findings challenge the conventional focus on temperature by identifying humidity as a critical regulatory factor in HCHO release, especially in environments where indoor temperatures remain below 25 °C. Lastly, the study outlines applicable, low-energy mitigation strategies—such as humidity regulation and seasonal control planning—aligned with the climatic realities of the Arabian Gulf. As González-Lezcano (2023) highlights, building design prepared for future environmental and health challenges must balance between energy efficiency and occupant health. This study advances that aim by providing empirically grounded insights applicable to the design of efficient and health-conscious social housing. These insights contribute to the development of resilient, sustainable IAQ management frameworks for social housing in hot, humid environments.

In this research, the analysis focused on temperature control behavior and the number of measurement points in the indoor environment of residential houses. This focus is consistent with previous IAQ studies that examined measurement protocols in similar contexts (Jung et al., 2022d; Al Horr et al., 2016). To minimize content variations, measurements were taken in newly constructed apartments with identical finishing materials and completed construction before occupancy, a practice also emphasized in earlier work (Kaunelienė et al., 2016). The measurement points were categorized into two groups—single measurement points and multiple consecutive measurement points—following established approaches in housing IAQ research (Földváry et al., 2017). A single measurement point involves taking measurements at a specific time in a house (Molina et al., 2020). Multiple consecutive measurement points refer to continuous measurements at various locations within the same house (Langer et al., 2016). The temperature control behavior was divided into autonomous and artificial control (Yousefi et al., 2017). These represent actual residential temperature management practices, in contrast to laboratory-imposed simulations. Autonomous temperature control refers to the natural adjustment of temperature without the use of air conditioning, relying on external air influences (D'Orazio and Maracchini, 2019). On the other hand, artificial temperature control involves deliberately manipulating the temperature using mechanical systems (Zhao et al., 2021).

Thus, the study focused on the relationship between temperature control behavior, humidity variations, and HCHO emissions, particularly emphasizing how different measurement methodologies capture IAQ dynamics (Dodson et al., 2017). Since temperature and humidity interact in real-world settings, the study systematically categorized measurements based on control mechanisms and the number of measurement points to analyze their impact on IAQ. The experiments and analyses were structured into six measurement scenarios, categorized by control type (artificial or autonomous) and measurement design (single or multiple points, including constant temperature maintenance).

1. Single measurement point with artificial temperature control (the artificial control section), where the effects of manually regulated temperature on IAQ were observed while monitoring humidity fluctuations.

The findings of this research provide valuable insights into the emission characteristics of HCHO in indoor environments, particularly in the context of Dubai’s climatic conditions and building practices. This research is distinguished from prior work by employing field data from actual residential buildings rather than relying on theoretical or laboratory-based experiments.

Our results confirm that humidity plays a more significant role than temperature in influencing HCHO emission rates in artificially controlled environments. This challenges conventional assumptions that temperature control alone is sufficient for managing HCHO levels. Conversely, temperature emerges as a dominant factor in autonomously controlled environments, indicating that tailored mitigation strategies are necessary depending on the indoor climate control approach.

A comparison of single-point and continuous measurements further highlights the variability of HCHO emissions, underscoring the need for long-term monitoring rather than isolated data collection. These insights contribute to a deeper understanding of IAQ management in hot climates and offer specific recommendations for maintaining healthier indoor environments.

The results highlight the substantial impact of temperature and humidity on the generation of HCHO (Mendell et al., 2018; Liang et al., 2016b). The investigation involved analyzing artificial and autonomous control sections in single-measurement houses to examine the relationship between temperature, humidity, and HCHO emission.

In the artificial control section, where the temperature was intentionally increased, no linear correlation was observed between temperature and HCHO emission (Mushtaha and Helmy, 2017). This suggests that HCHO emission in this section is not solely governed by temperature. However, an explicit dependency on humidity was identified, indicating that lower humidity levels contribute to higher HCHO emissions. These findings align with previous research emphasizing the crucial role of humidity in releasing chemicals from building materials.

In the autonomous control section, where temperature and humidity were naturally regulated, a significant temperature dependence on HCHO emission was observed. This indicates that controlling temperature in indoor environments can effectively mitigate the generation of HCHO (Jung et al., 2022a). Additionally, the results consistently demonstrated a dependence on humidity, indicating that higher humidity levels are associated with lower HCHO emissions. These findings support the notion that managing temperature and humidity is vital for controlling indoor air quality and reducing HCHO levels.

The analysis of multi-measurement houses further emphasized the impact of temperature and humidity on HCHO emission. The artificially controlled section exhibited a clear linear relationship between temperature and HCHO emission, indicating that higher temperatures result in increased HCHO generation. However, no significant dependency on humidity was observed in this section, suggesting that temperature control plays a more substantial role in HCHO emission compared to humidity control.

Variations were observed between individual houses in the autonomous control section of multi-measurement houses. Sobha Creek Vistas Tower A displayed a temperature-dependent trend, whereas Sobha Creek Vistas Reserve did not exhibit a linear relationship. However, both houses consistently demonstrated a dependence on humidity. These findings underscore the importance of considering specific house characteristics and management history when examining the dependencies between temperature and humidity.

Furthermore, in Sobha Creek Vistas Tower B, where a constant temperature of 25 °C was maintained, a strong temperature dependence on HCHO emission was evident. This confirms the effectiveness of maintaining a stable temperature in controlling HCHO levels in indoor environments. Overall, the results of this study reaffirm the substantial influence of temperature and humidity on HCHO emissions in residential houses in Dubai. Controlling temperature and humidity is an effective strategy for managing indoor air quality and reducing HCHO levels. However, it is essential to consider the unique characteristics of each house and its management history when implementing temperature and humidity control measures.

Additionally, variation in HCHO emission patterns across homes with identical layouts suggests that differences in construction details—such as the use of specific adhesives, finishes, and composite materials—as well as management history, including early ventilation practices and HVAC use, play a critical role. Homes that remained sealed or unventilated shortly after construction exhibited higher emissions, reinforcing the importance of post-construction indoor climate management.

This research presents a novel comparative approach to understanding formaldehyde (HCHO) emissions under different indoor temperature and humidity control behaviors in newly constructed residential buildings in Dubai. Unlike previous studies that relied on theoretical models or laboratory conditions, this study is grounded in empirical field data, with single-point measurements from 50 houses and continuous measurements from three. This approach provides a practical and region-specific understanding of pollutant dynamics in actual living environments.

Indoor climate control was categorized into two types: artificially controlled (mechanically regulated temperature) and autonomously controlled (naturally influenced temperature). Based on the findings, the following conclusions are drawn.

1. In continuously monitored houses, when indoor temperatures were artificially maintained at or above 25 °C, HCHO emissions showed a strong temperature dependence. However, in autonomously controlled environments with lower temperatures, humidity was the dominant factor influencing the outcome. This dual-behavior challenges conventional assumptions that prioritize temperature control alone.

These findings introduce new empirical evidence that challenges single-variable IAQ assumptions. The study demonstrates that in naturally regulated or energy-conscious housing environments, humidity control can be more effective than temperature regulation in mitigating HCHO emissions. It also highlights the value of continuous monitoring over isolated data points, particularly for developing predictive and responsive IAQ systems.

By integrating these insights, the research supports context-aware, low-energy mitigation strategies aligned with the sustainability goals of social housing development in the Arabian Gulf. The practical recommendations derived from real-use conditions make this study especially relevant for policymakers, designers, and housing authorities seeking to improve IAQ without compromising energy efficiency.

Moreover, the observed variation in emission patterns among homes with identical specifications suggests that the selection of construction materials and early post-construction ventilation practices have a significant influence on HCHO behavior. These factors should be considered when designing IAQ strategies for new residential developments.

Future work should explore the long-term effects of temperature and humidity fluctuations on HCHO emissions across various building materials and ventilation designs. This would support the development of robust policy frameworks and design guidelines tailored to the specific environmental and socio-economic conditions of hot-climate residential sectors. While this research is grounded in the Gulf context, its methodology and findings can be adapted for use in other climate zones, provided that local building materials and environmental conditions are taken into account.