Indoor Temperature Research Articles

Mechanically ventilated classrooms in central Italy's heritage school buildings: Proposal of archetypes and CO2 prediction models

This study proposed a typological analysis to identify the archetypes of classrooms equipped with controlled mechanical ventilation (CMV) in Italy and an experimental campaign on 58 typical classrooms to identify the main indoor microclimatic characteristics and CO2 concentrations. From the analyses carried out, general information was gathered on the heating systems and the main energy and acoustic improvements carried out in the schools. The typological analysis identified four different types of mechanical ventilation systems installed in three different classroom archetypes: wide, square and deep, with percentages of window area of 25 %, 30 % and 40 % respectively.The field measurement campaign showed that, in terms of CO2 concentration, mechanical ventilation was effective in the winter period, while in the mid-season and summer periods, natural ventilation was predominant due to the opening of windows by the occupants. Furthermore, in the case of manual control, incorrect use of the machine by the occupants, who reported noise-related problems or insufficient user training, resulted in CO2 levels above the recommended limits.Multivariate regressions developed for schools equipped with CMVs predicted maximum and average CO2 concentrations as a function of minimum and maximum indoor and outdoor temperatures with a significance (R2, correct) of 76 % and 83 % respectively.

Cold and costly to sweaty and stressed: how an NGO-led citizen science project measures indoor temperature to advocate for change

Cold and costly to sweaty and stressed: how an NGO-led citizen science project measures indoor temperature to advocate for change

Residential Indoor Temperatures and Health: A Systematic Review of Observational Studies

Residential Indoor Temperatures and Health: A Systematic Review of Observational Studies

Impact of refrigerant undercharge faults on building indoor conditions and HVAC system operation in residential Buildings: A simulation study

This study investigates the impact of refrigerant undercharge on indoor temperature and HVAC system performance in residential buildings. Simulation models for typical residential buildings in Orlando, FL and Indianapolis, IN were developed using the ResStock database. A refrigerant undercharge fault model was then applied to the simulations with varying levels of fault intensity. The paper offers an extensive analysis, revealing that variations in supply air temperature, equipment runtime, and cooling energy consumption due to the level of refrigerant undercharge faults are notably significant on a summer representative day. Similarly, on a winter representative day, changes in supply air temperature and runtime are significant as well as changes in supplemental heat energy consumption. We find that occupants may remain oblivious to these faults during the cooling season, particularly when the HVAC system is oversized; in that case, supply air temperature data could help detect a fault. Another challenge is that during the heating season, when the supplemental heater operates, it is difficult to identify a refrigerant undercharge fault using only indoor and supply air temperature data. This study finds that supply air temperature, equipment runtime, and supplemental heater energy consumption data can help in detecting refrigerant undercharge faults.

Simulation of low energy building thermal energy cycle in IoT smart city planning based on environmental sensors and deep learning

With the intensification of global climate change, the reduction of building energy consumption has become an important goal of smart city development. By optimizing the thermal energy circulation system, low energy buildings can not only reduce energy consumption, but also improve living comfort. In recent years, with the help of environmental sensors and deep learning technology, the intelligent management of building heat energy cycle has become a research hotspot. The research constructs an intelligent thermal energy circulation system that integrates multiple environmental sensors for real-time monitoring of indoor and outdoor temperature, humidity and other key environmental parameters. A deep learning algorithm is used to analyze the collected data to optimize the control strategy of the thermal energy cycle. Through simulation, the energy efficiency performance of the scheme under different climatic conditions and building types was evaluated. The experimental results show that the control strategy based on environmental sensors and deep learning can significantly improve the thermal energy utilization efficiency of low-energy buildings, and the average energy consumption is greatly reduced compared with the traditional management mode. The system shows good adaptability and stability under different climate conditions. Therefore, the application of environmental sensors and deep learning technology in the thermal energy cycle of low-energy buildings can effectively promote the energy efficiency management of smart cities.

Day-ahead optimal dispatching for airport integrated energy system based on load-storage coordination

Airports are characterized by high energy consumption, with the cooling supply load being the primary contributor. Fully exploiting the optimization potential by utilizing the elastic characteristics of cooling supply load is the key to energy saving and decarbonization of airports. Firstly, this paper proposes to build a load-storage integrated energy system architecture by incorporating the ice storage system; secondly, a day-ahead optimal dispatching model with the goal of minimizing operating costs and carbon emissions is established; finally, taking an airport as an example, the NSGA-II algorithm is applied to solving the model, and various typical scenarios are compared and analysed. The daily photovoltaic consumption rate and indoor temperature range are used to evaluate the dispatching results. The system optimal dispatching model improves its performance greatly compared to the design condition, with a reduction of 33.3% for the operating cost and 31.9% for the carbon emissions. Five scenarios are included in the optimization project to characterize different environmental conditions, and the results demonstrate that the proposed optimization model can almost achieve full photovoltaic consumption while ensuring that the indoor temperature is in the passengers' comfort zone in the face of different degrees of photovoltaic output fluctuations and outdoor temperatures. Research outcomes in this paper provide a reference for improving the energy flexibility potential of airports.

Optimization of indoor temperature sensor deployment in large spaces for multiple building operation scenarios using the genetic algorithm

Indoor Environmental Quality (IEQ) monitoring is significant for occupant comfort and system operation. Due to the complicated nature of the indoor environment, large spaces generally require an appropriate sensor deployment scheme for scientific, comprehensive, and cost-effective IEQ monitoring. However, most sensor deployment methods rely on manual experience without quantitative guidance. This study develops an optimization method for sensor deployment in large spaces by selecting air temperature as the targeted IEQ parameter. Three typical operation scenarios are considered separately and simultaneously for sensor deployment optimization. The effectiveness of the method has been demonstrated in an airport terminal. The results indicate that the proposed method outperforms the traditional methods in all scenarios. For each scenario, 20–30 (one per 300–450 m2) is the appropriate deployed number due to the marginal benefit decrease of additional sensors. Optimal deployed locations exhibit similarities and contradictions in different scenarios and trade-offs are required in a multi-objective optimization.

Investigation of dynamic start-up and thermal airflow characteristics for air-carrying energy heating and cooling system: Sidewall, ceiling, and composite walls

The dynamic start-up process of the air-carrying energy radiant system (ACERS) is crucial for operation control. The dynamic heat transfer process of sidewall, ceiling, and composite walls for air-carrying energy heating and cooling systems was investigated using field experiments and numerical simulation. A new dynamic start-up model was proposed to rapidly predict the dynamic response time and heat transfer surface temperature for controlling indoor temperature. Six schemes with different thermal flow characteristics resulting from temperature difference and velocity uniformity were quantitatively studied through numerical simulation, which helps determine their rationality. The results show that the dynamic start-up model aligns well with experimental data, with an error of less than 3 %. The fast response time of the air medium heat transfer surface for heating/cooling is short (less than 0.5 h). The ceiling provides better adjustability compared to the sidewall. In the unstable state (Gc < 0), the Gc-related buoyancy has a vertical promotion effect, leading to increased convection and decreased vertical temperature difference in the room. Adding the sidewall heating to the ceiling heating reduces the indoor vertical temperature difference by 23 % for the composite walls heating compared to the ceiling heating. Convection accounts for 27 % of the sidewall heating, which is 2.7 times higher than that of ceiling heating (11 %). Combining the dynamic start-up model with numerical analysis enables rapid prediction and analysis of the thermal performance of ACERS, which can be applied to advanced control and optimization for energy-saving applications.

Performance analysis of air-to-ground heat exchanger in equatorial Yaoundé: Hourly and daily thermal behaviour and efficiency optimization

This study examines an air-to-ground heat exchanger operating continuously during Yaoundé’s hottest month. The paper focuses on identifying cooling and heating periods based on the local thermal comfort range. We equally determine the duct length needed for 70 % efficiency at various air inlet speeds. Ground temperature measurements are taken to inform an analytical model predicting air outlet temperatures. Additionally, calculations are made for hourly thermal efficiency and potential. The results reveal ground temperatures ranging from 20.8 °C to 23.4 °C within 5 m of the surface. To achieve 70 % efficiency, duct lengths range from 44.3m to 48.7m depending on air inlet speed (0.5–1.5 m/s). The air-to-ground heat exchanger system can effectively cool buildings between 8am and 10pm, delivering comfortable air temperatures (23.5–25.5 °C). The air-to-ground heat exchanger can also provide heating from midnight to 5am before switching to cooling for the rest of the day. This demonstrates the potential of air-to-ground heat exchanger systems in equatorial climates to maintain comfortable indoor temperatures throughout the day by both heating and cooling buildings. The study's implications suggest that AGHEs can significantly enhance energy efficiency in building systems in equatorial regions, offering a sustainable solution for climate control. The novelty of this research lies in its detailed analysis of AGHE performance in a specific equatorial climate, addressing previously unexplored aspects of hourly and daily thermal behaviors, and providing valuable insights for optimizing AGHE systems in similar climates.

Thermal comfort in a two-storey malaysian terrace house: Are passive cooling methods sufficient in present and future climates?

Rising temperatures due to climate change will impact both the indoor thermal comfort of naturally-ventilated housing and the cooling energy needs of air-conditioned housing in tropical regions. This study aims to evaluate the impact of rising temperatures based on the IPCC A2 scenario on indoor thermal comfort and cooling energy in a typical Malaysian terrace house. It addresses three key questions: 1) Can passive cooling (PC) achieve future thermally acceptable conditions? 2) How will PC impact cooling energy with air conditioning (AC)? 3) What is the effectiveness of various PC methods, individually and combined, in controlling indoor climate and saving energy under present and future conditions? We evaluated the effectiveness of eight PC measures—including shading, insulation, solar reflectivity, and nighttime natural ventilation—using EnergyPlus simulations. Results indicate that without PC and AC, indoor temperatures range from 26 to 31 °C, rising to 29–36 °C by the 2050s, often exceeding ASHRAE 55 standards. Currently, combined PC and nighttime ventilation can improve thermal comfort time fraction by up to 87 %. However, by the 2050s, this drops to 38 %, indicating PC alone will be insufficient, and AC systems will be essential. Additionally, in an AC scenario, PC measures reduce cooling energy by 6 % compared to the baseline under future conditions, yet demand is 67 % higher than current conditions. These findings underscore the need for integrating both PC measures and efficient AC systems to mitigate future greenhouse gas emissions from residential sectors in Malaysia and other developing hot climate regions.

Experimental and analytical study of a reverse-bootstrap air refrigerator for fresh air-conditioning

ABSTRACT The use of hydrofluorocarbons as refrigerants is reduced because of the increasing greenhouse effect. Air refrigeration system is environmentally friendly with air as working medium. In this study, a reverse-bootstrap air refrigeration cycle was proposed for fresh air-conditioning, which eliminated the hot heat exchanger to reduce volume and weight, and a full fresh air refrigerator was developed and tested in a psychrometric test room. Combining the characteristic curves of a motor-driven turboexpander–compressor (MTEC), a numerical model was established to analyze system off-design performance. The relative deviations between the predictions and experimental data were within 10%. The test and calculation were conducted at standard conditions (the outdoor and indoor dry and wet bulb temperature is 35/24°C and 27/19°C, respectively). The MTEC operating at design rotating speed 38 krpm could supply fresh air with a flow rate of 517.4 kg/h and temperature of 12.0°C, and a cooling capacity of 2.93 kW was obtained with a system Coefficient of performance (COP) of 0.315. The optimal COP and corresponding rotating speed will change with the variation of environmental parameters. As the outdoor temperature increases from 32 to 38°C, the optimal COP decreases by 29.6% and the corresponding rotating speed increases from 39.6 to 47.6 krpm. Moreover, when the outdoor relative humidity increases from 35% to 55% and the indoor temperature increases from 23 to 31°C, the COP decreases by 36.8% and increases by 31.9%, respectively. The advanced exergy analysis indicate the system avoidable exergy destructions account for 54.9%. Under the avoidable conditions, the efficiency of compressor, expander, and motor is 0.85, 0.85, and 0.95, respectively, the system COP can reach 0.946. The exergy destruction analysis of components indicates the importance to optimize the compressor.

The Impact of Wall Structure with Photovoltaic Function on Prefabricated Buildings

The wall structure is the main load-bearing component of the prefabricated building, which plays an important role in the stability and aesthetics of the building. With the deepening of the application of new energy in the construction field, the application of photovoltaic wall with photovoltaic function is becoming more and more extensive. However, there is still controversy about whether the photovoltaic function can meet the requirements of the building. On this basis, this paper discusses the wall structure with photovoltaic function in depth, and analyzes its energy consumption, heat preservation, ventilation and cost indicators. The results show that the wall structure of photovoltaic function can improve the aesthetics of prefabricated buildings, meet customer demand rate of more than 75%, save energy consumption by 25%~30%, increase indoor temperature by 1~3 degrees, and ventilate at 1.2 levels. It can be inferred that the load-bearing wall of photovoltaic function is suitable for prefabricated buildings and has the potential and role of vigorous development.

Examining Energy Poverty among Vulnerable Women-Led Households in Urban Housing before and after COVID-19 Lockdown: A Case Study from a Neighbourhood in Madrid, Spain

People with lower incomes often live in homes with poor thermal properties, making it difficult for them to maintain a comfortable indoor temperature. This vulnerability is closely related to the quality and maintenance of housing, which negatively affects indoor environmental comfort, especially in terms of energy usage, having an impact on health and well-being. Studying energy poverty from a qualitative perspective allows us to delve deeper into the experience of these people. A qualitative study was carried out through a case study of women in a situation of household vulnerability and energy poverty. Semi-structured interviews were conducted with five women-led households and two key informants before and after the COVID-19 confinement, in one of the most vulnerable neighbourhoods of Madrid. Unveiling the complexity of this topic, three categories were identified: household composition and economic resources, perception and proposals for household improvements, and household health and well-being. Furthermore, the results suggest that reliance on inefficient solutions such as electric radiators or butane-cylinder heaters for space heating in winter (more affordable in the short term, but unsustainable in the long one) shows evidence of energy precariousness, which, together with other poor housing conditions and users’ behaviours, impact clearly on health, generating or worsening chronic diseases. Research in vulnerable populations requires interventions beyond visibility, supported by key informants. Social workers and educators are essential to improving the living conditions of the most vulnerable people; however, they need social policies and adequate intervention plans and strategies to support and make their efforts effective.

Study on the Coupling of Air-Source Heat Pumps (ASHPs) and Passive Heating in Cold Regions

Air-source heat pumps (ASHPs), as an active device, are widely used in building heating and cooling processes. However, in severe cold regions, they face reduced heating efficiency and frosting problems in winter. This paper proposes a new heating solution by coupling an ASHP with passive heating systems. It combines an ASHP with passive sunrooms and heat storage systems for heating. Through software simulations and mathematical modeling, the new scheme is compared and analyzed against traditional ASHP solutions to explore the performance of this scheme in rural houses in severe cold regions of China during winter. According to simulation and calculation analysis, on the coldest day of winter, the coupling scheme can provide approximately 99.41 kWh of heat to the indoors, which exceeds the 86.67 kWh required to maintain an indoor temperature of 20 °C. The system’s power consumption is 36.96 kWh, which is 66.88% lower than that of traditional heat pump heating. The study shows that the coupling system of an ASHP and passive heating has a good heating effect in severe cold regions. For the situation of insufficient solar energy at night, the design of phase-change materials and heat storage media can meet heating needs throughout the day.

A control strategy considering buildings’ thermal characteristics to mitigate heat supply-demand mismatches in district heating systems

In district heating systems (DHS), periodic heat supply-demand mismatches (HSDM) exacerbate issues such as thermal imbalance and hydraulic instability. To mitigate these issues, this paper proposes a supply water temperature correction strategy for heating stations that considers building's thermal characteristics. Firstly, buildings are classified into energy-saving levels based on comprehensive thermal characteristic Bc and heat load index. Secondly, simulation models are developed for buildings with different thermal characteristics, and response of indoor temperature to supply-demand mismatch rates was analyzed. Then, after determining the regulation sequence and supply water temperature of heating stations, a balanced control strategy is formulated for HSDM conditions. Finally, the proposed strategy was applied to a practical combined heat and power system (CHPS) in severe cold regions. The results showed that the studied heating stations were classified into 4 types. After regulation of both insufficient and excessive heating conditions, the indoor temperature guarantee rate increased by over 20 %; the ranges of thermal imbalance degree and hydraulic imbalance degree were reduced by more than 0.09 and 0.22, respectively; the SD of supply water pressure and supply-return pressure difference were reduced by over 0.17 and 0.11, respectively. The strategy provides a reference for global balanced control of DHS under similar HSDM conditions.

Flexibility enhancement of urban energy systems through coordinated space heating aggregation of numerous buildings

Due to the intrinsic flexibility of thermal energy in buildings, collective space heating can potentially offer significant benefits to urban energy systems. In this context, this study introduces a novel thermal energy normalisation approach to capturing the collective indoor temperature dynamics of clustered buildings. The feasible operational region of the normalised equivalent building thermal energy model is derived from individual building parameters and temperature requirements through the constraint-tightening technique. By employing the thermal energy normalisation approach, the aggregate flexibility of building populations is quantified and integrated into the energy management optimisation problem for the urban energy system operator. To associate the response of the normalised equivalent building model and individual building models, a deadbeat controller is designed to synchronise the energy levels and realise robust operation for buildings. Through a series of case studies, the simulation results demonstrate that the proposed preheating coordination strategy can facilitate energy savings for energy system operation, cost-effectively perform congestion management to ensure no local network is overloaded, and ensure the satisfaction of indoor temperature requirements.

Reflective coatings: Enhancing building performance and sustainability

Reflective coatings stand at the forefront of sustainable construction, offering a powerful solution to industry challenges posed by climate change, resource scarcity, and rising energy costs. These innovative coatings significantly enhance energy efficiency, improve thermal comfort, and contribute to urban heat management by reducing buildings' absorption of solar heat. This leads to a decreased reliance on air-conditioning systems, resulting in substantial energy savings and a lower carbon footprint for building operations. Our comprehensive study examines these coatings' application on roofs, walls, and windows, confirming their effectiveness in maintaining cooler building interiors and reducing the demand on mechanical cooling systems. By meticulously analyzing materials, application techniques, and modeling methodologies, the paper elucidates the coatings' pivotal role in promoting environmentally responsible building practices. The findings reveal that reflective coatings have the potential to reduce solar heat gain by about 40 %. This reduction can lead to a corresponding indoor temperature drop of 2–4°C in naturally ventilated buildings or a decrease in cooling energy use in air-conditioned buildings, provided the air conditioning system is not undersized. These energy savings are particularly significant in urban environments, where widespread adoption could potentially lower ambient temperatures by approximately 1°C, thus addressing the urban heat island (UHI) effect more effectively. In conclusion, our research offers a quantified assessment of reflective coatings, emphasizing their value within the broader discourse of environmentally responsible construction. Their substantial potential to support urban sustainability objectives is evident, marking them as a promising avenue for future development and implementation.

Study on photovoltaic combined air source heat pump heating system under typical meteorological conditions

Abstract This paper proposes a photovoltaic (PV) combined air source heat pump heating system for rural areas in severe cold regions of northern China, where the current clean heating methods have high costs and low efficiency. The paper uses meteonorm8 and TRNSYS software to derive the typical meteorological parameters and simulate the system performance in a guard room in Shenyang city. The paper analyzes the heat pump power consumption, PV cell power generation, and economic and environmental benefits of the system under different outdoor temperatures in the heating season. The results show that the system can meet the heating demand and maintain a comfortable indoor temperature, with an annual cost of 1603 RMB, which is 61.33% lower than a single heat pump system. The system can also reduce the emissions of carbon dioxide, sulfur dioxide, and dust by 2619.43 kg, 10.78 kg, and 6.91 kg per year, respectively, demonstrating its economic feasibility and environmental contribution.

Energy saving and carbon reduction of the application of phase change materials in rammed earth heritage buildings

ABSTRACT The combination of conventional thermal insulation materials and phase change materials (PCMs) was proposed without damaging the appearance of REHBs, the internal insulation measures of four types of expanded polystyrene (EPS) and six kinds of PCM boards combinations were investigated, and 19 retrofit cases were obtained. By conducting detailed simulations of energy consumption and indoor temperature for different cases at different locations, and comprehensively comparing multi-objects (energy-saving, economic and low-carbon), the energy consumption, cost recovery period and carbon reduction of these cases are compared and analyzed. The results show that Case I (only EPS) has the best energy-saving performance, economy and carbon emission reduction, Case III (EPS and PCM) is the second and Case II (only PCM) is the worst. The energy-saving rate of Case I and Case III (16 ℃) differs by 5.65%, while the cost, incremental benefit and payback period differ by 9.34%, 10.2%, and 1.57 years, respectively. Case III is a new and better passive retrofit measure of the REHB. Its energy-saving, cost and carbon reduction are only about 10% lower than that of Case I, but it has better indoor comfort. The outcomes can provide a reference for the innovative energy-saving retrofit cases for REHBs.

Exploring Systems Thinking and Systemic Design: Insights from a Summer School Experiment Addressing Urban Health Crises

This paper relates urban healthcare crises to the global challenges of overshoot and collapse and suggests systems thinking as an innovative approach towards addressing these amalgamated crisis situations. We begin by reviewing what systems are and how they are structured and behave, highlighting how systems thinking can identify high-leverage interventions and systemic design to achieve effective change. Subsequently, we illustrate how these system concepts were applied in an international, multidisciplinary summer school between European and Southeast Asian partners in collaboration with the World Health Organization’s (WHO) Technical Science for Health Network (Téchne). Examining how ventilation, temperature, humidity, and daylighting control strategies enhance Infection Prevention and Control (IPC), the initiative developed ideas and designs for a multiple disease treatment center that would provide isolation units and create a safe care environment for patients, families, and communities. The design process was informed through consultation with three physically and socio-economically diverse neighborhoods across the Bangkok Metropolitan Region to gain a richer understanding of the varied experiences and approaches in managing the COVID-19 disruption. Leveraging WHO guidelines, students adopted a systemic design approach to develop innovative solutions that could withstand natural hazards and used local materials and natural ventilation to prevent airborne infection and control indoor temperature. In conclusion, we propose a novel working model linking specific stages of systemic thinking and systemic design into a generalized, iterative urban and healthcare design framework that will be further refined as part of specific electives at the KU Leuven Faculty of Architecture and joint summer schools in 2023, 2024 and beyond.