Virtual Building Dataset for energy and indoor thermal comfort benchmarking of office buildings in Greece

The knowledge of building stock energy data of a country is a very significant tool for energy benchmarks establishment, energy rating procedures and building classification boundaries determination, according to the Directive 2002/91/EC and its implementation in EU Member States. The lack of building energy databases in many EU Countries, including Greece, and the difficulties of collecting them lead to the investigation of other potential solutions. The aim of this paper is to present a method of a Virtual Building Dataset (VBD) creation for office buildings in Greece. The philosophy of VBD is based on the creation and simulation of random office buildings that could be found or built in Greece, taking into account the Greek constructional and operational characteristics of office buildings and Greek legislation. The VBD consists of 30,000 buildings (10,000 in each climatic zone) with their detailed constructional and operational data and of their simulation outputs: the annual specific energy consumption for heating, cooling, artificial lighting, office equipment and an indoor thermal comfort indicator. Based on VBD results the energy and indoor thermal comfort benchmarks for office building sector in Greece are assessed and presented.     

Relationship between quality of building maintenance management services for indoor environmental quality and occupant satisfaction

Two surveys were carried out to investigate the correlation between building maintenance management services for indoor environmental quality (IEQ) and occupant satisfaction. Each maintenance management organization manager was surveyed using the Evaluation Index of Maintenance Management Service Quality, created by Akira Takakusagi. Seven office buildings in Seoul, Korea were investigated in the first survey, and two buildings from the first survey were selected for analysis in the second survey. One is a building with good maintenance management services but low occupant satisfaction, and the other is an office building with low maintenance management services but high occupant satisfaction.     

A new and innovative look at anti-insulation behaviour in building energy consumption

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.     

The impact of building-integrated photovoltaics on the energy demand of multi-family dwellings in Brazil

Brazil faces a continuous increase of energy demand and a decrease of available resources to expand the generation system. Residential buildings are responsible for 23% of the national electricity demand. Thus, it is necessary to search for new energy sources to both diversify and complement the energy mix. Building-integrated photovoltaic (BIPV) is building momentum worldwide and can be an interesting alternative for Brazil due its solar radiation characteristics. This work analyses the potential of seven BIPV technologies implemented in a residential prototype simulated in three different cities in Brazil (Natal, Brasília and Florianópolis). Simulations were performed using the software tool EnergyPlus to integrate PV power supply with building energy demand (domestic equipment and HVAC systems). The building model is a typical low-cost residential building for middle-class families, as massively constructed all over the country. Architectural input and heat gain schedules are defined from statistical data (Instituto Brasileiro de Geografia e Estatística—Brazilian Institute for Geography and Statistics (IBGE) and Sistema de Informações de Posses de Eletrodomésticos e Hábitos de Consumo—Consumer Habits and Appliance Ownership Information System (SIMPHA)). BIPV is considered in all opaque surfaces of the envelope. Results present an interesting potential for decentralized PV power supply even for vertical surfaces at low-latitude sites. In each façade, BIPV power supply can be directly linked to local climatic conditions. In general, for 30% of the year photovoltaic systems generate more energy than building demand, i.e., during this period it could be supplying the energy excess to the public electricity grid. Contrary to the common belief that vertical integration of PV is only suitable for high latitude countries, we show that there is a considerable amount of energy to be harvested from vertical façades at the sites investigated.     

The effect of suspended ceilings on energy performance and thermal comfort

The objective of this study is to determine the potential energy savings and thermal comfort benefits of exposing concrete in the ceiling to the indoor air as an alternative to suspended ceiling. The performances were assessed through monitoring of room air and surface temperatures in an office building in operation, and simulation of different scenarios with a calibrated building simulation model. In this study, it is shown that ESP-r is capable of simulating an advanced controlled office building in operation with good agreement with the measurements. The results presented in this paper indicate that exposed concrete in the ceiling both reduces the number of hours with excessive temperatures considerably and create a better and more stable thermal environment during the working day. Also, exposed concrete increases the achievements of utilizing night free cooling significantly. However, by removing the suspended ceiling, only minor annual heating energy savings are achieved.     

Perception of the thermal environment in high school and university classrooms: Subjective preferences and thermal comfort

This work shows some of the results of a field study about environmental comfort investigations in classrooms. In this project thermal, acoustic, visual and air quality aspects were analysed in a number of classrooms—13 classrooms at four different high schools of the Provincia di Torino and four typical medium-sized university classrooms of the Politecnico di Torino, Italy. The investigations were carried out during the heating period. Both field measurements and subjective surveys were performed at the same time during the regular lesson periods.     

Winter indoor air quality,thermal comfort and acoustic performance of newly built secondary schools in England

Previous studies have found that classrooms are often inadequately ventilated, with the resultant increased risk of negative impacts on the pupils. This paper describes a series of field measurements that investigated the indoor air quality, thermal comfort and acoustic performance of nine recently built secondary schools in England. The most significant conclusion is that the complex interaction between ventilation, thermal comfort and acoustics presents considerable challenges for designers. The study showed that while the acoustic standards are demanding it was possible to achieve natural ventilation designs that met the criteria for indoor ambient noise levels when external noise levels were not excessive. Most classrooms in the sample met the requirement of limiting the daily average CO₂ concentration to below 1500 ppm but just a few met the need to readily provide 8 l/s per person of fresh air under the easy control of the occupants. It would seem that the basic requirement of 1500 ppm of CO₂ is achieved as a consequence of the window areas being just sufficient to provide the minimum of 3 l/s per person at low and intermittent occupancy. Thermal comfort in the monitored classrooms was mostly acceptable but temperatures tended to be much higher in practice than the design assumed.     

Effects of thermal activated building systems in schools on thermal comfort in winter

There is a growing attention for the Indoor Air Quality problems in schools, but there is far less attention for the thermal comfort aspects within schools. A literature review is done to clear the effects of thermal quality in schools on the learning performance of the students: it clearly shows that thermal environment is like IAQ of great influence to the students' performance. As many studies focus on the ventilation aspects we focus more on the thermal comfort of the schools through measurements and questioners held in 14 schools equipped with different types of ventilation and heating systems.     

Analysis of thermal comfort and indoor air quality in a mechanically ventilated theatre

Theatres are the most complex of all auditorium structures environmentally. They usually have high heat loads, which are of a transient nature as audiences come and go, and from lighting which changes from scene to scene, and they generally have full or nearly full occupancy. Theatres also need to perform well acoustically, both for the spoken word and for music, and as sound amplification is less used than in other auditoria, background noise control is critically important. All these factors place constraints on the ventilation design, and if this is poor, it can lead to the deterioration of indoor air quality and thermal comfort. To analyse the level of indoor air quality and thermal comfort in a typical medium-sized mechanically ventilated theatre, and to identify where improvements could typically be made, a comprehensive post-occupancy evaluation study was carried out on a theatre in Belgrade. The evaluation, based on the results of monitoring (temperature, relative humidity, CO₂, air speed and heat flux) and modelling (CFD), as well as the assessment of comfort and health as perceived by occupants, has shown that for most of the monitored period the environmental parameters were within the standard limits of thermal comfort and IAQ. However, two important issues were identified, which should be borne in mind by theatre designers in the future. First, the calculated ventilation rates showed that the theatre was over-ventilated, which will have serious consequences for its energy consumption, and secondly, the displacement ventilation arrangement employed led to higher than expected complaints of cold discomfort, probably due to cold draughts around the occupants’ feet.     

室内空调条件下建筑围护结构屋面(墙、窗)的节能控制--建筑热环境与节能研究(之三)

在围护结构(屋顶、墙、窗)隔热控制的基础上,提出了屋顶、墙、窗的节能控制条件,窗——墙作用因子(算符)和隔热一节能作用因子(算符)。在已知墙的隔热控制指标条件下,可简单地计算出窗的隔热控制指标;同时,在已知墙、窗的隔热控制指标情况下,也可简单地计算出墙、窗的节能控制指标。     

Predictive control techniques for energy and indoor environmental quality management in buildings

The aim of the present paper is to present a model-based predictive controller, combined with a Building Energy Management System (BEMS). The overall system predicts the indoor environmental conditions of a specific building and selects the most appropriate actions so as to reach the set points and contribute to the indoor environmental quality by minimizing energy costs. The controller is tested using a BEMS installation in Hania, Crete, Greece.     

Occupant performance and building energy consumption with different philosophies of determining acceptable thermal conditions

Based on building energy and indoor environment simulations, this study uses a recently developed method relying on Bayesian Network theory to estimate and compare the consequences for occupant performance and energy consumption of applying temperature criteria set according to the adaptive model of thermal comfort and the more conventional PMV model. Simulations were carried out for an example building with two configurations (with and without mechanical cooling) located in tropical, subtropical, and temperate climate regions. Even though indoor temperatures differed significantly between building configurations, especially in the tropical climate, the estimated performance differed only modestly between configurations. However, energy consumption was always lower in buildings without mechanical cooling, particularly so in the tropical climate.     

A nodal thermal model for photovoltaic systems: Impact on building temperature fields and elements of validation for tropical and humid climatic conditions

This article deals with both an experimental study and a numerical model of the thermal behaviour of a building whose roof is equipped with photovoltaic panels (PV panels). The aim of this study is to show the impact of the PV panels in terms of level of insulation or solar protection for the building. Contrary to existing models, the one presented here will allow us to determine both the temperature field of the building and the electric production of the PV array. Moreover, an experimental study has been conducted in La Reunion Island, where the climate is tropical and humid, with a strong solar radiation. In such conditions, it is important to minimise the thermal load through the roof of the building. The thermal model is integrated in a building simulation code and is able to predict the thermal impact of PV panels installed on buildings in several configurations and also their production of electricity. Basically, the PV panel is considered as a complex wall within which coupled heat transfer occurs. Conduction, convection and radiation heat transfer equations are solved simultaneously to simulate the global thermal behaviour of the building envelope including the PV panels; this is an approach we call ‘integrated modelling’ of PV panels. The experimental study is used to give elements of validation for the numerical model and a sensitivity analysis has been run to put in evidence the governing parameters. It has been shown that the radiative properties of the PV panel have a great impact on the temperature field of the tested building and the determination of these parameters has to be taken with care.     

Control tuning of a simplified VAV system: Methodology and impact on energy consumption and IAQ

Nowadays, with the improvement of living standards, air-conditioning systems have been widely used causing more health problems linked to air-conditioning systems and indoor air quality. When an air handling unit is designed for a conference room, its variable use demands an outdoor air rate control in particular to optimize energy consumption of the new air heating/cooling. Based on an experimental site, the present work shows how to combine air quality and the improvement of energy consumption thanks to a way to define a control strategy. The control problem considered here is the management of air quality associated to a control of the outdoor air rates. A review of classical tuning methods is led in order to select suitable ones. Thus, a linearization of the phenomena must be done to border the system expression in tuning methods. Several classical methods are studied and the family model is chosen: monovariable and multivariable applications are brought to fruition. Simulations and applications permit to enhance energy consumption through the choice of a strict way to tune such control equipments.     

计算机模拟在建筑节能设计中的应用

依据DBJ13—62—2004《福建省居住建筑节能设计标准实施细则》,从节能率、成本、建筑热舒适性、节能方案适宜性等方面对比分析了规定性指标节能设计法与动态权衡计算设计法的优劣。得出计算机仿真模拟技术在建筑节能设计中应用的重要性。     

Optimization of energy consumption in buildings with hydronic heating systems considering thermal comfort by use of computer-based tools

The paper deals with an optimization of parameters, which influence the energy and investment cost as well as the thermal comfort. The parameters considered in this study are: the insulation thickness of the building envelope, the supply-water temperature and the heat exchange area of the radiators. A combination of the building energy simulation software EnergyPlus ¹ and the generic optimization program GenOpt (see footnote 1) has been used for this purpose. The paper presents the application of a one-objective optimization algorithm solving the problems with two objectives, because the optimization algorithm is one-objective and the problem has two objectives, which are minimal total costs and satisfied thermal comfort. The total costs represent the sum of energy consumption and the investment costs. The thermal comfort is represented by Predicted Percentage of Dissatisfied (PPD) in this study. The optimization is used to determine the values of parameters that give the lowest sum of investment and energy cost, under the condition that the thermal comfort is satisfied. In addition, the optimization processes show the mutual influence of parameters on both the total cost and the thermal comfort.     

Thermal study of school buildings in winter conditions

In this paper, a thermal study of a school building with real occupation levels in winter conditions is presented and a software that evaluates the air quality and simulates the thermal response of buildings with complex topology in steady-state and transient conditions is used. After validation, the numerical model is used, in the first phase, to evaluate the occupants’ comfort levels in several spaces, while in the second phase two solutions, to improve acceptable thermal comfort and air quality levels (1) the electric air-heating systems, with predicted mean vote control, and (2) three solar collectors, placed instead of the roof area, used to heat the air in uncomfortable spaces are studied.     

An internal assessment of the thermal comfort and daylighting conditions of a naturally ventilated building with an active glazed facade in a temperate climate

An active facade is often used to promote the flow of air through a building, however in order to ensure that this process is effective the facade should face a southerly orientation. This means that not only solar energy is transferred across the glazing but in sunny periods shading is needed to prevent excess brightness levels occurring on the working areas where it may result in the luminance distributions not complying with current lighting requirements. The building investigated is located in Sheffield, England and is one of the University of Sheffield's recently built green buildings. It has a high thermal mass which is used to promote the use of night cooling. This paper reports the initial findings of an internal assessment of the thermal comfort and daylighting conditions in such a building. The results have indicated that such designs are to be commended for their passive use of solar energy and can provide a high quality working environment.     

The influence of the external walls thermal inertia on the energy performance of well insulated buildings

Energy conscious building design consists in controlling the thermophysical characteristics of the building envelope such as, firstly, thermal transmittance (U-value). However, besides the U-value, the envelope thermal inertia should also be considered. The literature studies report very different estimations regarding the energy saving potential associated with the use of an adequate inertia, ranging from a few percentages to more than 80%. Therefore, this study aims at assessing the parameters enhancing or damping the role of thermal inertia, providing a variety of results. For this purpose several external wall systems with the same U-value but different dynamic properties were investigated to calculate the associated achievable energy savings. A parametric analysis was performed in progressive steps, by running the models of a virtual Test Cell and of a sample building. Both design parameters (heat transfer surface, solar control) and operational ones (ventilation rates, HVAC functional regime) were varied.It was found that the highest energy performance wall system has a proper combination of the dynamic thermal transmittance and thermal admittance values, although not necessarily the best ones. Moreover, it was shown that thermal inertia effects are enhanced if it is coupled with other energy saving measures and an efficient building use.     

Energy conservative building air conditioning system controlled and optimized using fuzzy-genetic algorithm

In this work, the combined effect of the energy conservative variable refrigerant volume (VRV) system and the variable air volume (VAV) system was experimentally investigated using genetic fuzzy optimization method that yielded better thermal comfort, indoor air quality (IAQ) requirements without compromising on the energy savings potential. The proposed system was tested using the demand controlled ventilation (DCV) combined with the economizer cycle ventilation (ECV) techniques and examined for a year-round building air conditioning (A/C) application. The supply air temperature (SAT) set points were varied under three distinct strategies and the optimal solutions obtained for the fuzzy systems designed resulted in an enhanced energy conservative potential. The test results of the proposed system were compared with the conventional fan coil A/C system. Based on the three strategies of the supply air temperature, the proposed system yielded an improved per day energy savings potential of 54% in summer and 61% in winter design conditions. Furthermore, for the strategies considered the proposed system achieved an annual energy conservative potential of 36% and exhibited more possible ways to achieve thermal comfort, IAQ and energy conservation.