Comfort In Buildings Research Articles

Optimizing hybrid ventilation and daylight-linked dimming control for carbon reduction and thermal comfort in a subtropical high-rise office building

The dominant contributors to electricity consumption in existing buildings are air-conditioning and lighting systems. This study aims to optimize hybrid ventilation and daylight-linked dimming control in a subtropical high-rise office building. The objective is to reduce carbon emissions while ensuring thermal and visual comfort. These two strategies can be retrofitted in a typical curtain wall system with vertical windows without encountering any technical limitations. EnergyPlus is used to analyze the impact of these strategies on enhancing thermal comfort and illuminance while achieving electricity savings in the high-rise office building. Based on the typical meteorological year of Hong Kong, using natural ventilation in perimeter zones can reduce the energy use intensity (EUI) by 2.6 to 3.41 % for 30.09 to 34.97 % of total operating hours, depending on window-to-wall ratios (WWRs). Furthermore, daylight-linked dimming control in perimeter zones can reduce EUI by 18.91 % to 21.9 % in the HVAC portion and 8.09 % to 12.25 % in the lighting portion during 91.39 % to 98.28 % of total operating hours. Using daylighting with a high WWR helps reduce 6.31 to 9.21 % in total greenhouse gas emissions. The study also develops a logistic regression model using three climatic variables to predict the natural ventilation status. Overall, the use of daylighting greatly improves the percentage of acceptable predicted mean vote (PMV), with the greatest improvements observed in perimeter zones facing east and west on the middle floors. However, the combined application of both strategies results in a tempered improvement. The novelty of this study lies in providing guidance on suitable WWRs for implementing both strategies to achieve carbon reduction. Moreover, the significance lies in providing a quantitative assessment of how enhanced ventilation and lighting controls contribute to lower carbon emissions while improving thermal comfort.

Assessment of acoustic comfort in a hostel building inside an educational campus

In the contemporary built environment, noise has emerged as one of the most pervasive and pressing issues across all building typologies. However, in recent times, an enhanced cognizance of the adverse impacts of noise pollution on human health has taken root. Specifically, within educational campuses, hostels, as the primary abode for most students, have been identified as sites where the assurance of indoor acoustic comfort is critical to bolster productive endeavors. However, the assessment of indoor acoustic comfort remains a less researched facet of indoor environmental quality. As a response to this knowledge lacuna, our research puts forth an innovative methodology that facilitates the assessment of the acoustic comfort of hostel buildings while meticulously analyzing the factors that impact the occupants' acoustic comfort. A case study hostel at the NIT Trichy campus has been selected, and two rooms from the same hostel block have been identified for further examination. The outdoor sound level is gauged at 2 meters from the facade, while the indoor sound level is assessed at the center of each room. Additionally, the reverberation time is measured in both rooms using the Bedrock SM 30 class -2 sound level meter. The collated data has been processed, and the results have been obtained. Furthermore, the methodology, as proposed by Project New TREND, has been employed to assign an acoustic class for each room. Room 1 has been categorized under class B, with a KPI of 4 points, while Room 2 has been allocated to class C, with a KPI of 3 points. This research posits a novel methodology that can enable designers to evaluate the acoustic class of hostels, which, in turn, can help them optimize facade elements to accentuate the indoor acoustic comfort.

A spatial mapping of thermal comfort and air quality (SMTC-AQ) framework for the built environment using computational fluid dynamics approach

Indoor environmental quality (IEQ), driven by thermal comfort and indoor air quality (IAQ), is a major factor that impacts occupant's well-being and productivity since people spend 80–90 % of their time indoors. The current approaches for assessing and quantifying IEQ presume fixed values and ranges in naturally ventilated (NV) spaces within the simulation environment. However, such an approach cannot capture point-to-point changes that occur in the built environment due to localized variations of environmental variables such as air velocity and temperature. This study proposes a sensing and simulation-based framework, Spatial Mapping of Thermal Comfort and Air Quality (SMTC-AQ) in a computational fluid dynamics (CFD) environment to address this. Salient characteristics of SMTC-AQ include the modification of predicted mean vote (PMV) for NV spaces, specifically for the Indian context, and the implementation of the under-explored concept of domain-decoupling utilizing the ISHRAE weather file. Using SMTC-AQ, the study determines the optimal window-to-wall ratio (WWR) and opening-to-wall ratio (OWR) for a case study room in an Indian academic building, considering both IAQ and thermal comfort. In the study, indoor air velocity and temperature are first validated with field data, followed by a scenario analysis to assess the impact of opening characteristics on IEQ. The findings show that for building spaces in tropical climates with moderate outdoor temperatures and lower relative humidity, thermal comfort, and IAQ can be improved by implementing higher WWR and OWR. Moreover, WWR is a more relevant criterion for improving thermal comfort and a better OWR design is crucial for enhancing IAQ in NV spaces.

Scalable Photochromic Film for Solar Heat and Daylight Management.

The adaptive control of sunlight through photochromic smart windows could have a huge impact on the energy efficiency and daylight comfort in buildings. However, the fabrication of inorganic nanoparticle and polymer composite photochromic films with a high contrast ratio and high transparency/low haze remains a challenge. Here, a solution method is presented for the in situ growth of copper-doped tungsten trioxide nanoparticles in polymethyl methacrylate, which allows a low-cost preparation of photochromic films with a high luminoustransparency (luminous transmittance Tlum = 91%) and scalability (30 × 350 cm2 ). High modulation of visible light (ΔTlum = 73%) and solar heat (modulation of solar transmittance ΔTsol = 73%, modulation of solar heat gain coefficient ΔSHGC = 0.5) of the film improves the indoor daylight comfort and energy efficiency. Simulation results show that low-e windows with the photochromic film applied can greatly enhance the energy efficiency and daylight comfort. This photochromic film presents an attractive strategy for achieving more energy-efficient buildings and carbon neutrality to combat global climate change.

A combined experimental and numerical analysis framework for the design of aluminum windows

Windows form an essential part of modern architecture owing to their crucial role in the energy efficiency of the building, functionality, durability, and aesthetic appeal. Despite their relevance, window designs are mainly carried out in an ad-hoc fashion. At the same time, more sophisticated approaches rely on trial-and-error experiments involving expensive custom die-casting and wind load experiments. This study proposes a robust numerical framework for economically designing new Aluminum window profiles. Specifically, we use a finite element model to determine the maximum threshold wind load and regions of failure for an Aluminum sliding window. The model is validated against experimental results. Further, a comparative study between windows made of regular 6063-Al alloy and Duranium™ (patented new aluminum alloy) is also performed to evaluate the role of material properties in the structural response of window sections. Interestingly, despite having comparable elastic modulus, we noted that the windows made of Duranium™ survive higher loads and exhibit significantly lower plasticity. Altogether, the present work demonstrates that the numerical model can accurately predict the failure patterns, loads, and deflections for the window frames and, hence, can easily be developed into an automated analysis framework for the optimal design of window frames. This could potentially improve the overall safety, comfort, energy efficiency, and sustainability of buildings at both the construction and usage stages.

Influence of cross-ventilation cooling potential on thermal comfort in high-rise buildings in a hot and humid climate

The rising cooling energy demand, caused by the increase in global average temperature and the frequency of heat waves, is currently leading to a significant increase in global electricity consumption. Passive cooling strategies, such as ventilative cooling, can provide acceptable indoor thermal comfort with no or minimal energy consumption, offering an alternative to air conditioning systems in buildings. This paper investigates the effectiveness of natural ventilation in an iconic post-modernist high-rise building in India: Charles Correa's Kanchanjunga Apartments. The research, employing CFD simulation paired with building energy simulation, demonstrates how cross-ventilation can improve the ventilative cooling efficiency in buildings, ensuring affordable indoor thermal conditions even in adverse climatic conditions like the Indian one. Thanks to night-time structural cooling, a maximum reduction in the operative temperature of up to 5.3 °C was achieved compared to the scenario without natural ventilation and up to 6.4 °C compared to the outdoor temperature peak on the hottest day. Consistently with the Indian Model for Adaptive Comfort, cross-ventilation ensures a reduction in discomfort hours of up to 58 % on the hottest day and a total reduction in discomfort hours on a typical monsoon and winter day. The paper aims to assist architects and policymakers in quantifying the cooling potential of natural ventilation in high-rise buildings, suggesting passive solutions for cooling energy saving.

“Hospital’s Thermo-neutral Zone for Patient Safety and Climate Change Sustainability

The efficacy of Iraq's direct heat recovery system is influenced by the nation's architectural design, particularly in view of the escalating climate conditions. There is an increasing worry on the necessity to openly address the local building patterns in Iraqi cities due to the challenging task of mechanically cooling buildings in the absence of electricity. The model was built using data obtained from field research carried out from January 2021 to March 2022. The field measurements of microclimatological parameters were carried out between March and August 2022 in order to evaluate the accuracy of the models. This methodology showcases the potential to make accurate predictions of future air temperatures by utilising variables as low as 5 percent. The air temperature decreases by 0.5 °C for every G increase across an area of 0.03-0.20 m2/m2, which is equivalent to a Leaf Area Index (LAI) of 4.5 m2/ha. This work introduces a standardized approach for assessing thermal comfort in real-world settings. The study examines the continuous use of hybrid ventilation systems at Kadhimiya Teaching Hospital to ensure a consistent air quality in the wards. Installing temperature control systems in these sites is vital to provide thermal comfort, as it serves as a potentially effective but expensive measure to address the impacts of climate change. Installing fans in military fortifications in Iraq seems to be a cost-efficient and uncomplicated approach to enhance their resilience against the escalating heat caused by the projected effects of global warming. However, when assessing the thermal comfort of buildings in Iraq's present and future climates, the established method proves to be considerably more advantageous.

Impact of Positioning Phase Change Materials on Thermal Performance of Buildings in Cold Climates

The building envelope, an essential component of any building, plays a critical role in meeting energy efficiency and thermal comfort requirements. Incorporating phase change materials (PCM) into the building envelope can offer an opportunity to minimize energy usage and enhance thermal comfort by offsetting daily temperature fluctuations. However, the optimal performance of PCM is contingent on the material’s placement and thickness within the building envelope. Therefore, this study investigated the effects of positioning and thickness of PCM on thermal comfort and heating loads in a lightweight timber building in Trondheim, Norway. Four scenarios were considered based on the positioning of the PCM layer in the exterior wall and roof. Using IDA ICE, parametric simulations were conducted for various PCM wallboard positions and thicknesses in the exterior wall and roof. In Nordic climates, adding PCM reduces the risk of annual overheating. The findings of this study showed that installing 75mm of PCM wallboard in the exterior wall’s inner layer reduced the annual heating load by 2.3%. Compared to the base case scenario, increasing PCM thickness reduced zonal maximum indoor air temperatures by up to 6.2°C. This study underscored the importance of carefully considering the placement and thickness of PCM in building envelopes for optimal performance.

Model predictive control for demand response in all-electric school buildings

This paper presents predictive control strategies for all-electric school buildings in cold regions to activate energy flexibility based on changes in electricity prices. A fully electric school building near Montreal, Canada, is used as a case study. This study investigates three scenarios: 1) Reference case with a proportional–integral controller and flat rate electricity price, 2) Model predictive control with flat rate electricity price, and 3) Model predictive control with dynamic electricity price. These scenarios are modelled using the resistance-capacitance thermal networks model, and energy performance is determined and compared over a typical heating season. The proposed approach takes into account the physical parameters of the building, weather predictions, and thermal comfort constraints to maintain optimal energy consumption. A building energy flexibility index is used to quantify the building energy flexibility with a focus on peak demand reduction when the electricity prices are higher than usual. The results show that the MPC strategy can reduce peak power demand by up to 100% and minimize the cost of electricity during demand response events while maintaining acceptable comfort conditions.

Assessment of Materials on Covid-19 Spread Prevention in Public Buildings

This research is an attempt to suppress the spread of COVID-19 in public buildings through the application of materials that may prevent the spreading of SARS-CoV-2 while at the same time improving audial comfort in such buildings. Study on the capability of materials to break further spreading of the virus applied by measuring the presence of SARS-CoV-2 RNA on the material based on exposure time (0, 3, 6, and 9 minutes). This RNA tracing procedure is repeated on the surface of aluminum, tiles, carbon steel, glass, gypsum, copper, and painted cement on the wall. The results showed that the CT value (cycle threshold) of all materials was approximately 25, which means that they still have the potential to spread the virus. Slightly different results occur on the gypsum surface where the viral envelope (gene E) is not detected with a CT value of 36, meaning no chance of the virus spreading. The same materials will undergo measurement of sound absorptive characteristics to assess their effect on the audial comfort in the building. The results of the study are expected to be a reference before their application as interior materials in public buildings.

Design and Management of a Spatial Database for Monitoring Building Comfort and Safety

As the impacts of climate change on urban environments and buildings become more and more prominent, building comfort and structural safety monitoring becomes crucial. However, efficiently storing and managing the multi-source monitoring data generated during the long-term monitoring process has been an urgent challenge. In order to solve the above problems, this paper designs and develops a spatial database management system for building comfort and structural safety monitoring based on standard database development tools. A conceptual model of a spatial database for building comfort and structural safety monitoring is proposed, and the entities, attributes, and connections in the model are discussed to transform the E-R conceptual model into a logical model supported by an object-relational spatial database management system. Based on this conceptual and logical model, a mainstream backend framework was adopted and combined with common database and programming language tools and BIM (Building Information Modeling) technology for development to establish a spatial database management system with data storage, management, analysis, and visualization functions. We designed building monitoring experiments and proved through the experiments that the database management system can stably store, analyze, and manage the monitoring data and visualize the display, with the advantages of a fast response speed and low error rate. The spatial database system improves the storage and management efficiency of building comfort and structural safety monitoring data, eliminates redundant data, and realizes comprehensive analysis and management of building comfort and structural safety monitoring data. It provides data support for building comfort and structural safety assessment, helps users analyze the formation mechanism and evolution law of the urban heat island effect, assesses the interrelationship between climate change and urban building morphology, and constructs an urban thermal environment that is more adaptable to climate change.

SOCIALIZATION OF THERMAL COMFORT STANDARDS AT SMKN 4 SOUTH TANGERANG

Vocational High School (SMK) is a formal education unit that provides education that prepares students to work in specific fields. Students can continue their vocational education after completing their education at the junior high school level. SMK Negeri 4 South Tangerang is one of the 4th Vocational High Schools in the City of South Tangerang, specializing in Building Modeling and Information Design, Health Services, Animation, and Visual Communication Design. SMKN 4 South Tangerang is located on Jalan Sumatra-Tidore, Jombang Village, Ciputat District, South Tangerang City, Banten Province, with a land area of 4,562 m2. Currently, SMK Negeri 4 South Tangerang uses a natural air circulation system with openings in each class; then, each class uses a fan for artificial air circulation. There are four types of building comfort: thermal comfort, space comfort, and audio comfort. Space comfort is related to the comfort of movement space and relationships between spaces. Meanwhile, thermal comfort is an essential part of building comfort because room temperature influences the feeling of comfort. This is because every human being has sensors on their skin that work when there are hot or cold temperatures. Thermal comfort conditions that comply with standards will help the teaching and learning process be streamlined at SMK Negeri 4 South Tangerang. So that SMK Negeri 4 South Tangerang has thermal comfort that meets standards, Budi Luhur University organizes Community Service activities to socialize the achievement of thermal comfort at SMK Negeri 4 South Tangerang. The method of implementing activities uses the concept of Problem Solving. At the same time, the Problem-Solving concept uses input stages, problem-solving processes, and output. The aim of socializing the achievement of thermal comfort is so that the management of SMK Negeri 4 South Tangerang knows how to achieve thermal comfort standards so that students at the School are comfortable when carrying out the teaching process.

Meta data analysis on building thermal management using phase change materials

Despite the extensive research conducted on phase change materials (PCM) and their effect on thermal comfort in buildings around the globe, there is still a lack of clarity regarding the direction of development and performance in this field of study. A comprehensive analysis employing bibliometrics and text-mining techniques was conducted to provide a multi dimensional overview on the role of PCMs in building thermal management. The Web of Science database was mined to collect research publication patterns and information across three decades concerning PCM deployment in building thermal management. Vos Viewer, Biblioshiny, Microsoft Excel, and orange data mining were used to analyze the corpus. The publications tally in this domain was comparatively low till 2005 but saw a dramatic uptick from 2016 onwards. China (215), India (71), and Italy (47) have the highest publication count. Finland (234) and New Zealand (166.1) have the highest average article citations. Zhang Zhengguo has authored the most papers in this discipline (17 publications). Still, Farid, Mohammed M (1571) and Luisa F. Cabeza (1405) are highly cited authors. Phase change material is the most used keyword. Additional findings include prominent institutions, authorship networks/collaborations, and the journal with maximum citations. According to the sentiment analysis of abstracts, 97.79 % of researchers are optimistic about building thermal management using PCMs. The research outcomes of this study will deliver significant contributions to the field and serve as a reference point for scholars and decision-makers as they confront the challenge of rising energy consumption and thermal comfort in buildings.

Investigation of indoor thermal comfort of heritage buildings in hot summer and cold winter zone of China: A case study

The heritage buildings of a country or region are frequently considered to be of value and significance to the current generation. This study investigates the winter indoor thermal comfort of heritage buildings in hot summer and cold winter zone of China. Field measurements and questionnaire surveys were used to conduct specific studies on the winter indoor thermal comfort of two typical traditional residential buildings (“Yinziwu” and “Diaojiaolou”) in the Yuan River basin heritage building area. The aim is to investigate the current status of building thermal comfort and provide a theoretical basis for promoting their sustainable development. The results show that 1) Indoor air temperatures in both types of buildings are significantly and positively correlated in winter, but both are below the human thermal comfort range. 2) Mean air temperatures measured in "Yinziwu" and "Diaojiaolou" are 8.8 °C and 9.4 °C, respectively, with neutral air temperatures of 11.1 °C and 13.8 °C. 3) Thermal sensation, thermal preference, and thermal comfort were significantly correlated in the two buildings, with ooccupants experiencing the coldest phase from 7:00–11:00 and the warmest phase from 15:00–19:00 daily. 4) "Yinziwu" occupants are more tolerant of the cold climate.

The impact of facade geometry on visual comfort and energy consumption in an office building in different climates

In recent years, there has been a heightened emphasis improving visual comfort and energy efficiency. Various solutions have been explored to achieve high-performance design. Shading devices play a crucial role in enhancing building performance by redusing solar gains, excessive daylight, and improving both energy efficiency and occupants' visual comfort. This research aims to investigate the effect of facade geometry on visual comfort and energy consumption in four different climates of Iran and categorize each variable based on effectiveness for each location. Parametric office modeling was done by using Grasshopper and Rhino software. Then, the effect of the facade on the interior lighting and energy consumption was analyzed by Radiance, Daysim, and EnergyPlus calculation engines. The Non-Dominated Sorting Genetic Algorithm (NSGA-II) was selected to optimize solutions, minimize energy consumption, maximize useful daylight illuminance, and view quality. In addition, the methodology was used to explore the framework for optimizing office facade design in Iran's diverse climatic zones. The simulation results indicate that window-to-wall ratio and inclined wall were essential for balancing daylighting performance and energy consumption. This research stated that using a self-shading design could increase the quality of view up to 75% while reducing energy consumption and the risk of glare. Results proposed a design framework to improve visual comfort and save energy. The rotating façade's wall 10°-30° reduced cooling energy demand and energy usage intensity in selected models. So, an inclined wall could be an efficient shading device to improve building's performance in Iran.

Analysis of Heating Energy Consumption of School Buildings in Shigatse, Tibet

This paper is launched against the background of excessive heating energy consumption in China, continuous calls for sustainable development, and unsatisfactory heating energy use in primary and secondary schools in Shigatse, Xizang. Through field research on the existing school buildings in Shigatse, Xizang, a large number of first-hand materials were obtained, and then through targeted summary and classification of the data, the key problems leading to high energy consumption, low clean energy utilization rate and poor thermal comfort of school buildings in Shigatse, Xizang were found. On this basis, further analysis will be conducted to address the issue, seeking ways and methods to utilize clean energy technologies such as solar heating to solve the heating problem in school teaching buildings.

Thermal Comfort Temperature Evaluation in Hospital Wards for Patient Safety and Climate Change Sustainability

The quality of Iraq's direct heat recovery system is affected by the country's construction design, particularly in light of the warming climate Reference Minimum 26.6 C Reference Average Air Temperature38.6 C,. There is growing concern that the local building patterns need to be addressed openly because the lack of electricity makes the mechanical cooling of buildings difficult in Iraqi cities. This methodology demonstrates the capability to generate precise forecasts of forthcoming air temperatures by using variables as little as 5 percent. This paper presents a standardized methodology for evaluating thermal comfort in the field. The study analyzes the hybrid ventilation systems utilized by Kadhimiya Teaching Hospital round-the-clock to maintain the constant air quality in the wards. Installing climate control is crucial in these locations to maintain thermal comfort as a potentially powerful but costly response to climate change. Adding fans to military fortifications in Iraq appears to be a cost-effective and simple method to improve their resistance to the extreme heat that is anticipated to become more common due to global warming. However, in evaluating the thermal comfort of buildings in Iraq's current and future climates, the established method is significantly more useful.

Calibrating subjective data biases and model predictive uncertainties in machine learning-based thermal perception predictions

Heating, Ventilation, and Air Conditioning (HVAC) systems in large-scale buildings often struggle to ensure satisfactory thermal comfort for diverse occupants while minimizing energy waste. Achieving this goal requires developing reliable prediction models that capture the changing and varied occupant thermal perceptions in different spaces. Despite their widespread use, many machine learning (ML) based prediction models suffer from subjective data biases and model predictive uncertainties, causing inaccurate estimation for occupant needs and leading to suboptimal building controls. The authors propose a data-model integration method that identifies and calibrates the inherent uncertainties of existing ML models in both data and model dimensions, ensuring reliable thermal perception predictions. This method introduces the Multidimensional Association Rule Mining (M-ARM) algorithm to identify biased human responses by exploring interrelationships among four perception metrics: thermal sensation, comfort, acceptability, and preference. Our method reveals significant performance enhancements in seven ML models, enhancing the F1-score by up to 5.53%. By leveraging reliability diagrams and Expected Calibration Error (ECE) scores, we also expose the models’ vulnerability to miscalibration and the need for calibrated predictions. We further evaluate six calibration techniques (e.g., Platt Scaling and Isotonic Calibration) on these models and uncover their potential to enhance prediction reliability performance, highlighting a reduction of up to 80.66% in ECE scores. The authors also investigated the impacts of dataset sizes, classifiers, and calibration methods on the proposed method. Our research offers insight into creating robust data-driven strategies for thermal perception predictions, ultimately contributing to optimized occupant comfort and energy efficiency in buildings.

A Comprehensive Assessment of Indoor Air Quality and Thermal Comfort in Educational Buildings in the Mediterranean Climate

Maintaining good indoor air quality and thermal comfort is a challenge for naturally ventilated educational buildings, as it can be difficult to achieve both aspects simultaneously. Nonetheless, most of the existing studies only focus on one aspect. To explore the potential of balancing indoor air quality and thermal comfort, both topics must be investigated concurrently. This study assessed indoor air quality and thermal comfort in 32 naturally ventilated classrooms of 16 primary and secondary schools in the Mediterranean climate, based on a large on-site measurement campaign lasting one year that gathered over 460 hours of data. The research investigated occupants’ adaptive behaviors, analyzed the actual thermal comfort of around 600 students, and characterized the representative scenarios leading to good and poor indoor air quality and thermal comfort by clustering analysis. The results showed that poor indoor air quality was mainly due to closing windows and doors in winter, while thermal discomfort mainly occurred in summer because of the high indoor temperature. The findings suggested that a proper ventilation protocol is the key to balancing indoor air quality and thermal comfort.

Correlation of AC energy consumption and passive thermal comfort with floor levels in tropical high-rise residential dwellings

The relationship between thermal comfort, building floor levels, and HVAC energy consumption in tropical high-rise residential buildings remains unclear. These buildings face heavy cooling demands due to their immense height and volume, as well as hot-humid weather found in the tropics. Architects and building developers understand that an increase in a building's floor count increases its energy requirements, but the impact on occupant thermal requirements and AC energy consumption needs further investigation. This study aimed to evaluate the relationship between passive thermal comfort, AC energy consumption, and floor levels in tropical high-rise residential buildings through survey and experimental methods. The results showed a significant relationship between thermal sensation votes and building floor levels, as well as AC energy consumption and floor levels. The study also found a strong correlation between thermal sensation votes and predicted mean votes, AC energy use, and predicted people dissatisfied. The optimal cut-off floors for thermal dissatisfaction according to (TSV) are 22nd floor and 8th floor in summer and monsoon seasons respectively. With a 90% sensitivity and 92% specificity. This research highlights the importance of addressing thermal comfort in high-rise buildings to improve energy efficiency and thermal comfort in tropical climates.