Comfort Levels In Buildings Research Articles

Acoustic and thermal properties of panels made of fruit stones waste with coconut fibre

Using natural porous and fibrous materials for acoustic and thermal conditioning in the construction sector is a solution to achieve a comfort level in buildings. The novelty of this research work lies in employing agricultural and agro-industry waste to solve noise and thermal insulation problems. This study was conducted to investigate a multilayered panel made of fruit stones and coconut fibre from agro-industry waste. Acoustic absorption, and acoustic and thermal transmission, tests were run on four different fruit stone types, olive, cherry, apricot and peach, plus a coconut fibre layer. Although they are not structural elements, bending tests were run to ensure panels’ structural integrity. Acoustic tests complied with the recommendations of Standards ISO 10534–2 and ASTM E 2611–09, based on the standing wave tube to obtain the acoustic absorption coefficient and sound transmission loss, respectively. Standard EN 12667 was considered for the thermal test to determine the thermal conductivity coefficient based on the hot plate method. The results show an average sound absorption coefficient above 0.5 and sound insulation over 25 dB within certain frequency ranges. The cherry panels had absorption values of around 0.7 and apricots had sound insulation values of up to 30 dB. Samples’ thermal transmittance coefficient values were between 3.0 and 3.4 (W/m2K), which indicate panels’ ability to provide thermal insulation. The cherry and olive panels obtained the lowest thermal conductivity (around 0.14 W/mK). The backing effect of the coconut fibre layer improves all the panels’ acoustic absorption and thermal properties.

Innovative cementitious mortar incorporated with sepiolite based shape-stable phase change material for thermal controlling of buildings

In light of the urgent demand for enhanced temperature control within the realm of construction and building applications, this research presents an innovative shape-stabilized phase change material (PCM). Effective thermal energy storage has been made possible by combining myristic acid (MA) and lauric acid (LA) with sepiolite in cement mortars. These innovative PCM-incorporated mortars present promising solutions for reducing daytime cooling loads and enhancing thermal comfort in buildings. The research thoroughly examines the influence of Sepiolite infused with PCM on the thermoregulatory efficiency of cement mortar in specially designed test chambers simulating real ambient conditions. The research findings underscore the material's remarkable thermal stability, reliability, and capacity to efficiently absorb and release substantial latent heat. The study discloses the latent heat storage properties of the SEP/LA-MA composite, with 79.01 J/g absorbed during melting and 78.67 J/g released during solidification. Thermal durability, evaluated through 500 consecutive cycles, demonstrates consistent phase transition characteristics. Post-cycling, the composite maintains an impressive 78.68 J/g latent heat of fusion, retaining 99.5% of its original capacity. The TGA results emphasize the exceptional thermal stability of Sepiolite, LA-MA, and the composite, underscoring their ability to withstand typical operating conditions effectively. The introduction of these innovative cement-based composites with shape-stable PCM holds significant potential for enhancing various building components, aiming to elevate both energy efficiency and comfort levels in buildings.

The Application of UAVs in the Evaluation of Thermal Comfort Levels in Buildings Equipped with Internal Greenhouses

A greenhouse is used to improve thermal comfort (TC) levels for its occupants in winter conditions using solar radiation, which involves low energy consumption. The aim of this research is the application of unmanned aerial vehicles (UAVs) in the evaluation of thermal comfort levels in buildings equipped with internal greenhouses. The new building design is developed numerically, and a building thermal simulator (BTS) numerical model calculates the indoor environmental variables. A new alternative and expeditious method to measure occupants’ comfort levels using UAV technology is applied using a UAV dynamic simulator (UAV DS). The evolution of the measured variables used for evaluating the predicted mean vote (PMV) is compared using the two numerical methodologies: BTS and UAV DS. In the second one, the mean radiant temperature (MRT) measuring methodology, the floor temperature, the lateral walls’ temperatures, the ceiling temperatures, and the air temperature are applied. In the method presented in this paper, a new building design is developed numerically, which includes a central greenhouse equipped with a semispherical dome, four auditoriums distributed around the central greenhouse, occupant distribution, and a ventilation methodology. The building geometry, the solar radiation on transparent surfaces, the TC, and the UAV mission methods are presented. The results show that, in general, the central greenhouse and the ventilation methodologies provide acceptable TC levels. The UAV monitoring mission, which includes two vehicles, provides good environmental variable replication, particularly when the environmental variables present greater variations. In the auditorium and greenhouse, the ceiling and lateral surface temperatures, respectively, can be used as an MRT approximation. The BTS numerical model is also important for developing buildings using renewable energy sources to improve the TC levels.

Assessment of the dynamic thermal behaviour of a test room using computer simulations and experimental measurements

People spend most of the time indoors and adequate comfort level in buildings is fundamental for their well-being and productivity. These issues can be investigated using both simulation models and experimental measurements in dedicated laboratories or in real buildings. The numerical and experimental approaches need to be combined in order to overcome the limitations of each one. This paper presents the application of a detailed numerical model to the CORE-CARE laboratory built at the University of Padua, a test room employed for indoor environmental quality (IEQ) evaluations. The HVAC plant consists of a mechanical ventilation unit and radiant systems for space heating and cooling. Each radiant surface presents different constructive characteristics and can operate independently. The test room is a novelty in this panorama, as it was integrated in an existing building, as a room for regular use. The impossibility of controlling external disturbances makes the dynamic modelling of the room extremely important, for the laboratory control and knowledge. For this reason, the test room behaviour in response to different HVAC system settings and external disturbances is analysed. Two experimental campaigns were carried out both in the heating and cooling seasons, activating one surface at a time, in order to both validate the model and set-up the transient thermal behaviour of the laboratory. In summer, three experimental set-ups were arranged: closed blinds, opened blinds and presence of a thermal dummy. The data analysis highlights that the North surface exhibits the fastest response in both seasons, whereas the floor is the slowest due to its inertia. In summer, the active surface equilibrium temperature is closer to the water supply temperature for responsive and massive surfaces, and it rises with incoming solar radiation and thermal dummy heat gain. The cooled floor enhances the space's thermal stratification. Simulation results show that the model reproduces the system's real dynamics, with a maximum RMSE of 2.3 and 1.9 °C for the North surface and air temperature.

Green glass space based design for the driven of sustainable cities: A case study

• Green glass space was proposed driven by energy efficiency and thermal comfort. • Seasonal operation characteristics and design parameters of GGS were explored. • GGS can decrease heating energy consumption by about 50% compared with N-GGS. • ADPI is above 85% and PD is below 1% at various heights and angles of GGS. • The optimal design parameters of GGS are at a height of 0.9 h and an angle of 90°. Demand for thermal comfort is high in regions characterized by hot summers and cold winters. Active solutions commonly used to improve comfort level in buildings may increase energy consumption, which hinders the sustainable development of cities. It is of great significance to balance the comfort and energy during the building design phase. Passive solutions present the potential in energy saving, such as glass curtain wall. However, it is difficult to ensure thermal stability in building because of the unsteady heat exchange through glass curtain wall, further affecting the balance. In this work, transitional space consisting of glass façade, i.e., green glass space (GGS), between indoor and outdoor environments is proposed to achieve a favorable balance. The impacts of design parameters (i.e., height and angle of green glass space) are investigated on both thermal comfort and energy efficiency, which are carried out in a case study. Numerical simulation is validated by experimental data. Air distribution performance index (ADPI) and percentage of dissatisfied (PD) are used as indicators to evaluate thermal comfort. Energy saving coefficient is put forward as an index for energy efficiency of green glass space. Results showed that (1) green glass space can decrease heating energy consumption by approximately 50% compared with non-green glass spaces, (2) air distribution performance index is above 85% and percentage of dissatisfied is below 1% at various heights and angles, and (3) optimal design parameters of green glass space are achieved at a height of 0.9 H (H is the building height) and an angle of 90° This study can provide an important reference of design strategy for the sustainable development of green building and cities.

Automatic fouling detection in district heating substations: Methodology and tests

Diagnosis of anomalies in heat exchangers of district heating substations is an essential point to assure high comfort level in buildings, as well as to exploit energy sources efficiently. The aim of this paper is to propose a methodology for automatically detecting fouling in the heat exchangers located in the substations of a district heating system. The methodology is tailored for large district heating networks, where a large number of buildings should be examined with reasonable availability of data. Fouling is analysed using only the data collected by the meters installed in the substations: the mass flow rate on the primary side and the temperatures on both sides of the heat exchanger. Evaluation is difficult due to the rawness of the data gathered and the variable operating conditions, which are adjusted on the basis of the external temperatures and set-points. The software created to implement the proposed methodology receives rough data as the input and it is able to manage data gap and lack of data. Furthermore, it provides a graphical output, which can be used for assisting the operators who manage the network and plan the cleaning schedules. The software has been tested considering space heating substations in six distribution networks of the Turin district heating system, for a total amount of 325 heat exchangers. A regular application of the approach and the cleaning of the heat exchangers presenting fouling is expected to lead to an average annual decrease of about 1.6% of the primary energy consumption in the entire network.

Numerical modeling of transient heat transfer in a phase change composite thermal energy storage (PCC-TES) system for air conditioning applications

This paper presents a detailed numerical analysis to describe the transient heat transfer in a phase change composite-thermal energy storage (PCC-TES) system exchanging heat with a heat transfer fluid. The “PCC-TES” is precisely composed of 78% low temperature paraffin, namely n-Tetradecane (C14H30) and 22% expanded graphite) and a heat transfer fluid (namely, ethylene glycol). Such detailed numerical approach to precisely describe the heat exchange between this specifically proposed phase change composite thermal energy storage (PCC-TES) and the heat transfer fluid has not been yet addressed in literature. The mathematical modeling of the PCC-TES involves formulating two PDEs that represent conduction within the PCC (phase 1) and advection within the heat transfer fluid (phase 2). The two coupled PDEs were solved with a finite difference method. Numerics were implemented using Fortran. Results were validated using experimental data and demonstrated acceptable agreement and an accurate representation of this specific transient heat transfer problem. The variations between experimental time traces of temperature and numerically calculated data are estimated at approximately (4–9%) and attributed to the heat loss in the actual experiment. Accordingly, the slabs in the actual experiment needed a longer time to reach the temperature of the Ethylene Glycol entering the PCC-TES structure from the inlet at the top. The paper also demonstrated that a lumped-parameter ODE model can perform an incredibly good job of predicting the enthalpy uptake of the PCC precisely matching the PDE results for the enthalpy uptake of the PCC due to the high thermal conductivity of the graphite. The proposed PCC-TES system will be integrated with air conditioning systems to efficiently meet cooling demand and reduce emissions. Previous work by our research group has demonstrated that the [AC + PCC-TES] hybrid design can reduce compressor size by 50%, double the compressor efficiency (COP) during mid/off-peak hours, reduce electricity consumption by 30%, and cut CO2 emissions by 30% – all without compromising overall system performance or building comfort level.

Energy Saving Potential of a Combined Solar and Natural Gas-Assisted Vapor Absorption Building Cooling System

A building energy simulation study is carried out to analyze the performance of a triple-hybrid single-effect vapor absorption cooling system (VACS) operated by solar, natural gas, and auxiliary electricity-based cogeneration. A high capacity small office building subjected to different climatic conditions is considered. The system is designed to continuously maintain a specified building comfort level throughout the year under diverse environmental conditions. Simulations are done at different generator temperatures to investigate the performance in terms of total annual electric energy consumption, heating energy, and the coefficient of performance (COP). The performance of the present VACS is compared with the conventional compression-based system, which demonstrates the electric energy and cost saving potentials of the proposed VACS. Simulation outcomes are well-validated against benchmark data from national renewable energy laboratory and energy conservation building code. Interestingly, it is found that beyond a certain collector area, surplus energy savings can be acquired with the present triple-hybrid VACS as compared to the compression-based cooling. Results also show that COP of the simulated system is in line with experimental values available in the literature. Finally, recommendations are given to operate the complete system on solar and biomass resources, which provide encouraging opportunity for agriculture-based countries.

Thermal Performance of Lightweight Aggregate Concrete Containing Expanded Shale Aggregates

Achieving energy efficiency of building in north part of Kazakhstan is very critical due to the large temperature difference during long harsh and severe winter and short hot summer seasons. Energy efficient building shows significant savings to homeowners including costs reduction from energy, water, waste, and lower operations and maintenance costs. In terms of building materials, lightweight aggregate concrete (LWAC) due to its thermal properties is often used to maintain thermal comfort levels in buildings and to reduce building energy consumption. In this paper, the potential of LWAC to improve the energy performance of building was assessed for LWAC with three different mixture proportions and a normal weight concrete (NWC) for comparison purpose. The energy saving effect of LWAC was simulated using OpenStudio software tools with an EnergyPlus engine. Moreover, annual heat loss and amount of heat transfer of construction wall of building were calculated. Results showed that LWAC can improve the energy efficiency of building and thus the use of LWAC can be a good alternative to the traditional NWC.

Современные тенденции в проектировании систем теплогазоснабжения и вентиляции

The article presents the review and analysis of current trends in the design of systems of heat and ventilation. Examines two major trends in designing modern systems of heat and ventilation: the use of technologies that increase energy efficiency and improve environmental air conditions of buildings. It is noted that the development of technologies for processing air, increasing energy efficiency, continues to be a priority in the field of heating, ventilation and air conditioning. An important trend is the increased attention to the creation of ecology air mode in areas at early stages of development of the architectural concept of the building. Discusses the features and applications tipovyh pumps in buildings and facilities. Discusses the peculiarities of installing underground storage of heat and cold in aquifers, which have proliferated in recent years. The features of technology «cooling ceilings» to improve comfort levels in buildings.

Experimental and numerical investigation of a dew-point cooling system for thermal comfort in buildings

Using the latent heat of evaporation of water as a natural driving energy resource, indirect evaporative cooling (IEC) systems can decrease air temperature without increasing its moisture content. The performance of any evaporative cooling system is largely dependent on the structure and design of the heat and mass exchanger. By modifying the exchanger of the IEC system, air could be cooled below its wet bub temperature and towards the dew point temperature. In this study a numerical analysis is carried out for a modified dew point cooling system based on a proposed psychrometric energy core (PEC) with a cross-flow heat and mass exchanger for buildings air-conditioning applications. A detailed numerical model was developed for the energy core with the cross-flow exchanger using Matlab. The coupled heat and mass transfer equations were solved using a fully implicit accurate finite difference scheme to predict air temperature and humidity distribution throughout the dry and wet channels. With an intake air of 30°C temperature and 50% relative humidity and a working-to-intake air flow ratio of 0.33, the system attained a wet bulb effectiveness of 112% and a dew point effectiveness of 78% with 5mm channel height and 500mm channel length. In addition, an experimental setup was built and a dew-point cooler with a cross-flow heat and mass exchanger was tested to assess the feasibility of using such dew point cooling systems under various operational and ambient conditions. The numerical model developed was validated using published data in addition to the experimental results. Using the validated model, a parametric study was carried out for a dew-point cooler with cross-flow heat and mass exchanger to investigate the effect of different operational parameters on the overall performance and to optimize the cooling system performance to achieve the indicated thermal comfort levels in buildings.

Potential energy savings from cool roofs in Spain and Andalusia

Cool roofs are an inexpensive method to save energy and to improve the comfort level in buildings in mild and hot climates. A high scale implementation of cool roofs in Andalusia, in the south of Spain, could potentially save 295,000 kWh per year, considering only residential buildings with flat roofs using electrical heating. At the current energy prices, consumers can save 59 million euros annually in electricity costs and the emission of 136,000 metric tons of CO2 can be directly avoided every year from the production of that electricity. If radiative forcings are considered, Andalucía can potentially offset between 9.44 and 12 Mt of CO2. All the provinces in the rest of Spain are also studied in this paper. The biggest savings are achieved in Gran Canaria (48%), Tenerife (48%), Cádiz (36%), Murcia (33%), Huelva (30%), Málaga (29%), Almería (29%) and Sevilla (28%), where savings are greater than 2 euros per square meter of flat roof for old buildings with dark roofs. For the biggest cities the range of savings obtained are: between 7.4% and 11% in Madrid, between 12% and 18% in Barcelona and between 14% and 20% in Valencia.

Thermal and environmental assessment of a passive building equipped with an earth-to-air heat exchanger in France

In France, where a division by 4 of the greenhouse gases emissions is aimed from 1990 to 2050, technical solutions are studied in order to reduce energy consumption while providing a satisfactory thermal comfort level in buildings. A two-dwelling passive building has been carried out in Formerie (North-West of France), complying the “Passivhaus” standard. This building, not yet monitored, has been modeled using the dynamic simulation software COMFIE, which is dedicated to building eco-design. In order to account for the implemented ventilation system, including a heat recovery unit and an earth-to-air heat exchanger, a specific model has been developed and integrated to COMFIE as a new module. In this article, this model is described first. In order to quantify the benefits brought by a passive design, the simulation results are presented for the passive house and a reference house complying with the French thermal regulation for buildings. The heating load and thermal comfort level of both houses are compared, showing for the passive design a tenfold reduction of the heating load and a clear reduction of summer discomfort. Finally, the environmental assessment – carried out with the life cycle assessment tool EQUER – shows the reduction in primary energy consumption, global warming potential and other impacts brought by the passive house design. Passive house appears to be an adequate solution to improve the environmental performances of buildings in the French context.

Choosing the Right Parameter for Single-Duct Constant Air Volume System Supply Air Temperature Reset

To improve system efficiency under part-load conditions, the supply air temperature set point for a single-duct constant air volume air handling unit (AHU) system is often reset based on either return air temperature or outside air temperature. Both reset strategies make engineering sense as long as the reset schedules are reasonable. Quite often the decision to use one over the other is made with the assumption that they will both achieve some energy savings. However, the impact of these two strategies on AHU energy consumption could be very different. An in-depth analysis and comparison of these two commonly used supply air temperature reset strategies for a single-duct constant air volume system is presented in this paper. It is shown that the reset strategy based on outside air temperature is inherently better than that based on return air temperature, with lower energy consumption and improved building comfort level.

A qualitative study of facilities and their environmental performance

Improving indoor environmental conditions and, thus, health standards will have a direct impact on the performance of the employees and, thus, organisations and on the wealth of the community. The indoor air quality, lighting, ergonomics, acoustics and health complaints scales are widely used to determine building performance levels. The research model was tested using responses from 362 employees in 25 diverse hospitals. The results indicate that building comfort level assessments play a critical role in influencing the health complaints and building general sufficiency level judgements of the employees. These judgements differ from each other for the hospital groups classified according to the ownership criteria. This study will support a better evaluation of development policies of workplace environmental conditions by managers.