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• This paper quantifies model errors in fan pressurization tests in windy anisothermal conditions. • Maximum error is characterized with fan-induced, weather-induced, and reference pressures. • Both the power-law and the quadratic law can yield significant errors at low pressures. • Possibilities for testing in windy anisothermal conditions are extended compared to ISO 9972. Building pressurization test methods assume that the flow through building envelopes follows a power law or a quadratic law with a specific correction to account for wind and stack effects. This paper investigates the model error stemming from these assumptions using a numerical approach. The model developed calculates the air flow rate through a building envelope assuming it can be viewed as an array of parallel cracks following a quadratic law. On the one hand, the model gives the ideal leakage air flow rate at a given reference pressure across all leaks; on the other hand, it calculates the leakage air flow rate at the same reference pressure that would be obtained with a pressurization test. In calm isothermal conditions, sensitivity analyses show the error in the leakage air flow rate is in the range of –32% to 0% and −15% to 25% at 4 Pa for the quadratic and the power laws, respectively; it is in the range of 0% to 1.5% and −1% to 0.7% at 50 Pa. In windy anisothermal conditions, the range of the relative error strongly depends on the constraints put on the induced pressures. In our analyses, ISO 9972 constraints disqualify a significant number of tests without reducing the maximum error. The results obtained on a very large number of tests enabled us to derive a simple relationship between the maximum error on the leakage air flow rate, the fan-induced pressure, the weather-induced pressure, and the reference pressure. This relationship could be used for estimating uncertainties in pressurization tests for a given building in given weather conditions without invalidating tests a priori based on criteria such as the zero-flow pressure or the wind speed. The discussion details the model limitations. Note in particular that it applies only to steady weather conditions. Further research is necessary to consider unsteady conditions which are common in the field. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the findings of a case study with building simulation using EnergyPlus dynamic thermal simulation software, in which wall insulation was varied together with cooling set-point temperature in a hot and dry climate of Botswana. Against the established norm that adding wall insulation reduces annual fuel consumption, it is shown in this paper that this is not always the case: there are instances where adding wall insulation directly increases annual fuel consumption. Initial cost of insulation aside, as the cooling set-point temperature is gradually increased, the building switches from an “insulation reduces cooling load” to an “insulation increases cooling load” behaviour. In other words, the well established knowledge that “the lower the u-value the better” gets overridden by “the higher the u-value the better”. We termed this a “point of thermal inflexion”. Simple graphical demonstration of the existence of this point is presented in the paper. According to the findings, design engineers and building economics related professionals who quantify investment on insulation can get disastrous results if they assume that all buildings behave pro-insulation since a building may behave anti-insulation. [Copyright &y& Elsevier]

Providing a comfortable and pleasant indoor environment for the occupants is the primary objective of an efficient ventilation process. Therefore, it is important to gain a proper understanding between the interaction of airflow and the occupants which determines the ultimate ventilation strategy and as one of the final outcomes, the architecture layout itself. The CFD (Computational Fluid Dynamics) methods provide an accurate and robust tool to simulate the complex airflow structure in enclosed spaces. Among the CFD simulation approaches, the large eddy simulation (LES) and its hybrid variants such as detached eddy simulation (DES) provides the information on the flow behavior by modeling the small turbulent structures of the airflow encountered in an indoor environment. These methods are highly sensitive to the boundary conditions which are the pivotal factors in an indoor airflow modeling and its accuracy. The main objectives of this paper are: (a) to assess the performance of different LES and DES models in capturing velocity and thermal fields (b) to investigate the effect of manikin’s shape on the accuracy of predictions. Three LES SGS (sub-grid scale) and one DES models are applied in this study considering the cases with and without the radiation from the manikin. Moreover, the effect of simplifying the manikins’ geometry on velocity and thermal distribution is investigated. Results showed that a detailed manikin shape can provide more accurate predictions (4–10%) at some locations, especially those close to the manikin’s body. As for performance of the applied models, Comparisons showed that ZEM and WALE models provide a better predictions of velocity and temperature fields by 3–10% at different locations. [ABSTRACT FROM AUTHOR]

A major challenge in applying Model Predictive Control (MPC) to building automation and control (BAC) is the development of a simplified mathematical model of the building for real-time control with fast response times. However, building models are highly complex due to nonlinearities in heat and mass transfer processes of the building itself and the accompanying air-conditioning and mechanical ventilation systems. This paper proposes a method to develop an integrated state-space model (SSM) for indoor air temperature, radiant temperature, humidity and Predicted Mean Vote (PMV) index suitable for fast real-time multiple objectives optimization. Using the model, a multi-objective MPC controller is developed and its performance is evaluated through a case study on the BCA SkyLab test bed facility in Singapore. The runtime of the MPC controller is less than 0.1 s per optimization, which is suitable for real-time BAC applications. Compared to the conventional ON/OFF control, the MPC controller can achieve up to 19.4% energy savings while keeping the PMV index within the acceptable comfort range. When the MPC controller is adjusted to be thermal-comfort-dominant that achieves a neutral PMV index at most office hours, the system can still bring about 6% in energy savings as compared to the conventional ON/OFF control. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated a potential reduction in cooling load and improvement in comfort from the implementation of night ventilation. This paper describes the performance, in terms of indoor environmental conditions, of three buildings from both the U.S. and India that use night ventilation as their primary cooling method. The research methods used the following approach: (1) Assess the cooling strategy in relation to the adaptive comfort model; (2) Develop a hybrid model, using both first principle equations and the collected data, to predict the instantaneous air and mass temperatures within each building and use the model to assess performance of the cooling strategy; (3) Determine an optimized ventilation control strategy for each building to minimize energy and maintain comfortable temperatures. (4) Develop a statistical model using collected data to predict the window opening pattern for occupants of a building using natural night ventilation. The study yielded the following results: (1) The buildings in the mild climate are successfully keeping the indoor temperature low, but also tend to be overcooling; (2) The night ventilation strategy has very little impact on indoor conditions of the buildings in the mild climate; (3) The impact of night ventilation is less significant when there is low internal loads and heavy mass; (4) The building in the hot and humid climate is keeping the indoor temperature within the comfort bounds for 88% of the year; (5) The night ventilation strategy has advantageous impact on indoor conditons of the building in the hot and humid climate, but not enough to cool the space on its own; (6) Model predictive control has the potential to further improve the performance of night ventilation. (7) Window opening behavior for the building using natural night ventilation is most heavily dependent on indoor air temperature and mass temperature. [ABSTRACT FROM AUTHOR]

• ENVI-met is used to compare microclimate between two scenarios, original and adapted. • Upgrading of buildings can enhance thermal comfort in adapting existing urban setting. • Planting new trees improves thermal comfort in urban densification. • Assessing microclimatic parameters is required within urban planning and design. Extensive transformations of large housing estates in postsocialist cities have been the subject of many studies. However, the effects of transformations resulting from urban densification, upon local microclimate, have not been fully determined. This paper addresses this issue by investigating the implications that vertical extension of residential buildings had on microclimatic parameters of thermal comfort (air temperature, mean radiant temperature, wind speed, relative humidity, solar radiation) in three large housing estates in the city of Niš, Serbia. By using ENVI-met software, outdoor microclimate is simulated in two scenarios: (1) original urban setting and (2) current urban setting, after the upgrade of existing buildings with additional floors. For the scenario with upgraded buildings, results indicate a small decrease in daytime air temperature, and small increases in mean radiant temperature and nocturnal air temperature. The effects on air temperature, relative humidity and solar radiation are more visible when upgrading low-rise structures, while the upgrade of high-rise buildings mostly affects wind speed. Research identifies tools and strategies of urban design that help in adapting inherited urban settings to temperature increase, such as positioning vertical extensions to exploit the effects of shading, conceptualizing open space in regard to building form, wind speed and solar radiation, and capitalizing on the cooling potential of trees. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims at studying the energy impact of a chilled ceiling displacement ventilation CC/DV system aided with a personalized evaporative cooler (PEC) directed towards the occupant trunk and face. A simulation model is developed for integrating the personalized cooler with the ascending thermal plume. The thermal model of the conditioned room air around the person is integrated with a segmental bioheat and thermal comfort model to predict the human thermal comfort. The model is validated with experimental data on the vertical temperature distribution in the room, and the recorded overall comfort perceived by surveyed subjects. Experimental results agreed well with predicted values of temperature and comfort level. When using personalized cooling, the DV supply air temperature can be as high as 24°C while the PEC at flow rates of 3–10l/s achieved similar comfort with a DV system at supply temperature of 21°C. At equal thermal comfort level, the integrated CC/DV system, PEC model resulted in up to 17.5% energy savings compared to the CC/DV system without a PEC. When mixed air is used in the CC/DV system additional 25% savings in energy is realized when compared with energy used for the 100% fresh air without the PEC. [Copyright &y& Elsevier]

Abstract: The combination of chilled ceiling and displacement ventilation systems can cause destruction of the displacement flow pattern in some circumstances. This paper reports on the performance of a new technique for achieving stable conditions for displacement airflow in the presence of a chilled ceiling system. The technique is based on the attachment of a honeycomb slat system to the underside of a chilled ceiling, thereby suppressing downward cool natural convection. Investigations were carried out using both computational and experimental methods for a range of typical office environment conditions. The results showed that a slat depth to width ratio of 10 could suppress the natural convection by more than 80% when the Rayleigh number reached 7×106. This confirms that the technique is capable of minimising downward cool air currents, resulting in preservation of the displacement flow pattern in the presence of the chilled ceiling. The proposed slat system can raise the general air temperature in the space allowing some displacement flow pattern to occur. The outcome of this study is the emergence of a honeycomb slat-based approach for improving the performance, together with provision of general advice for designers as regards the combination of radiant cooling/displacement ventilation systems. [Copyright &y& Elsevier]

Abstract: A retrofit study was conducted in an unoccupied manufactured house to investigate the impacts of airtightening on ventilation rates and energy consumption. This paper describes the retrofits and the results of the pre- and post-retrofit assessment of building airtightness, ventilation, and energy use. Building envelope and air distribution systems airtightness were measured using fan pressurization. Air change rates were measured continuously using the tracer gas decay technique. Energy consumption associated with heating and cooling was monitored through measurement of gas consumption by the forced-air furnace for heating and electricity use by the air-conditioning system for cooling. The results of the study show that the retrofits reduced building envelope leakage by about 18% and duct leakage by about 80%. The reduction in the house infiltration rates depended on weather conditions and the manner in which the heating and cooling system was controlled, but in general these rates were reduced by about one third. The energy consumption of the house for heating and cooling was reduced by only about 10%, which is relatively small but not totally unexpected given that infiltration only accounts for a portion of the heating and cooling load. [Copyright &y& Elsevier]

Abstract: In Thailand, traditional houses and public buildings were constructed from materials of low thermal mass. Windows and doors in such buildings are well shaded. Open windows, doors, and even gaps in the raised floor allow all interior spaces in a building to be naturally ventilated. Prior to the introduction of air-conditioning, concrete began to replace wood as walling material. New large air-conditioned buildings have glazed and closed windows so all interior spaces require air-conditioning and forced ventilation. Under the present situation, there is a tendency to believe in the merit of thermally massive walls. This paper presents results from an experimental and simulation study on comparative energy and economic performance of thermally light and massive walls that are used to enclose air-conditioned spaces. The spaces are assumed to serve three residential functions and three commercial functions. Results related to residential functions reaffirm the merits of vernacular architecture. Results related to commercial functions are mixed. However, very massive walls are not economical. [Copyright &y& Elsevier]

Abstract: The paper presents an extensive experimental and numerical study on a cross-ventilated building providing important features of the induced flow patterns at the two openings as a function of the free stream wind velocity''s magnitude and its incidence angle. The experimental data are measured via anemometers across the openings, whilst the numerical methodology is based on the time-dependant solution of the governing Navier–Stokes equations. The experimental data are compared to the corresponding numerical results, revealing the unsteady character of the flow field especially at large incidence angles. Furthermore, additional information regarding the flow field near the opening edges, not easily extracted by experimental methods, provide an in depth sight in the main characteristics of the flow field both at the openings but also inside the building. Finally, a new methodology for the approximation of the volume flow rate aerating the building based on experimental measurements of the velocity field at the openings is presented. [Copyright &y& Elsevier]

Abstract: Integration of building materials incorporating PCMs into the building envelope can result in increased efficiency of the built environment. A PCM-enhanced wall system is proposed in this paper and a simplified model for the heat exchange between the indoor environment and ambient was developed. The objective of the study was to assess the effect of occupancy pattern and ventilation on the energy savings potential of the wall system. It was found that (1) the occupancy pattern influences the value of the PCM melting point for which maximum energy savings value was reached and (2) the ventilation and its pattern reduces the relative value of the energy savings. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the experimental study of a solar-assisted ground-coupled heat pump system (SAGCHPS) with solar seasonal thermal storage installed in a detached house in Harbin. The solar seasonal thermal storage was conducted throughout the non-heating seasons. In summer, the soil was used as the heat sink to cool the building directly. In winter, the solar energy was used as a priority, and the building was heated by a ground-coupled heat pump (GCHP) and solar collectors alternately. The results show that the system can meet the heating–cooling energy needs of the building. In the heating mode, the heat directly supplied by solar collectors accounted for 49.7% of the total heating output, and the average coefficient of performance (COP) of the heat pump and the system were 4.29 and 6.55, respectively. In the cooling mode, the COP of the system reached 21.35, as the heat pump was not necessary to be started. After a year of operation, the heat extracted from the soil by the heat pump accounted for 75.5% of the heat stored by solar seasonal thermal storage. The excess heat raised the soil temperature to a higher level, which was favorable for increasing the COP of the heat pump. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the numerical three-dimensional prediction of the induced flow patterns around and inside a building, which is cross-ventilated in a natural way. The air change rate is controlled by two opposite openings on the building envelope, as a function of wind velocity and its incidence angle. The numerical methodology is based on the finite volume numerical solution of the Navier–Stokes equations, using the CFD commercial code FLUENT. The numerical results are compared with available experimental data regarding the refresh rate of the building''s room and the relative velocity profiles at the window openings, indicating a good agreement. Furthermore, a detailed description of the natural ventilation process is provided, whilst additional information regarding the induced velocity and pressure field is presented; information which cannot be easily extrapolated by experimental methodologies. Finally, the impact of the inner topology of the building on the induced flow field is investigated. [Copyright &y& Elsevier]

Abstract: Limiting heat losses during ventilation of indoor building spaces has become a basic aim for architects, particularly since the oil crisis of 1970. Much experience has been gained in terms of ventilation of indoor spaces. Nevertheless, due to the complex applications, attempts to create a theoretical base for solving the problems related to the issue are limited, especially determining the minimum ventilation period required within a designated space. In this paper we have approached this matter, both theoretically and experimentally. The conclusion we reached was that controlled ventilation of spaces through vent holes that successively open and close at regular time intervals can limit the excessive circulation of air masses, which in turn limits heat losses. [Copyright &y& Elsevier]

Abstract: A full-scale ventilated roof component was tested under real climatic conditions. Key constructional parameters, such as the air gap height and application or not of a layer of a radiant barrier, were examined during the tests and the performance of the component was assessed by direct comparison to a simultaneously operating conventionally constructed roof. The experimental results of the summer period are presented in this paper. The direct comparison with the conventional roof indicates significantly improved performance of the ventilated component. [Copyright &y& Elsevier]

Abstract: Green roof utilisation has been known since ancient times both in hot and cold climates. Nowadays, it has been reconsidered at issue of energy saving and pollution reduction. In this paper, some measurement sessions on a green roof installed by the Vicenza Hospital are described. A data logging system with temperature, humidity, rainfall, radiation, etc. sensors surveyed both the parameters related to the green roof and to the rooms underneath. The aim is to evaluate the passive cooling, stressing the evapotranspiration role in summer time. Furthermore, the enhanced insulating properties have been tested during winter time. A predictive numerical model has been developed in a building simulation software (TRNSYS) to calculate thermal and energy performances of a building with a green roof, varying the meteorological dataset for a specific geographic zone. [Copyright &y& Elsevier]

The present paper explores experimentally induced ventilation of a one-story detached real-size building. The building is a small well-insulated manufactured home. It is located at the Northern edge of the Negev desert in Israel.The flow of air inside the building is induced by a hot element heated by solar radiation. This element is a horizontal metal sheet mounted above the roof of the building and forming a duct connected to the inner space of the building. Heated air flows out of the duct while fresh air is sucked into the manufactured home from the surroundings.An extensive experimental study was based on continuous temperature monitoring performed inside and outside the building in summer. Velocity measurements inside the building were performed, as well. Typical experimental runs took from 12 h to a few days.The results show that effective induced ventilation has been achieved, and the air temperature inside the structure typically followed the ambient temperature. In contrast, when the manufactured home had no openings, the temperature inside it was considerably higher than the ambient, especially during the afternoon hours. [Copyright &y& Elsevier]

There is one primary goal and several secondary goals to fulfill when designing a heating, ventilation and air conditioning (HVAC) system. The main goal is to create an indoor climate that satisfies the user and this should be achieved in the most energy efficient way and with a system that also function in a long-term perspective. Higher supply air flow have the potential of increasing office workers performance and decreasing short-term sick leave. To increase the supply air flow, a cooling function is added to the air and 100% outdoor air is supplied. The main objective of this paper is to give the fundamentals for a system design that takes good indoor climate, energy efficiency and long-term operation into account. When controlling the static pressure at branch level, it is possible to vary the air flow to different zones without measuring the individual flow and without affecting the air flow to other zones. An equation for the placement of the pressure sensor is shown and the relative flow difference between the diffusers on the branch is calculated and measured. These principals are the fundamentals for a pressure controlled variable air volume (VAV) system. The fan pressure set point is optimized resulting in a decreased fan power requirement and sound generation. The flow to each zone is controlled at the diffuser outlet which prevents draft and therefore a wide range in supply air temperature can be used. [Copyright &y& Elsevier]