Search

Urban overheating is the most documented phenomenon of climate change impacting humans. This article presents the most recent developments on the magnitude and characteristics of urban overheating and the potential synergies with global climatic change. It analyses the latest qualitative and quantitative data on the impact of higher urban temperatures on buildings' energy supply and demand, heat-related mortality, morbidity and wellbeing, human productivity, survivability of low-income populations, and environmental quality of cities. It describes the state of the art on the development of innovative mitigation materials, advanced urban greenery, heat dissipation, and evaporative techniques as the main mitigation and adaptation technologies to offset the impact of urban overheating. It also analyses the current knowledge on the impact of each mitigation technology on energy, health, environmental quality, urban economy, and survivability. Finally, this article presents the main future challenges related to urban overheating and proposes a specific research agenda to alleviate and counterbalance its impact on human life. [ABSTRACT FROM AUTHOR]

Income, housing unit size, number of appliances owned and other components of socio-economic status (SES), are variables generally considered to influence residential energy use. Using structural equation modeling of SES indicators from the U.S. residential energy consumption survey (RECS), we provide evidence that SES, usually modeled as a latent construct with effect indicators, is better conceptualized as including at least some causal indicators. We studied the mediating effect of housing unit size and number of owned appliances on the relationship between SES, household size and residential energy consumption (REC). We found that household size was positively associated with REC, as a direct effect. SES had a strong impact on REC, while being mediated by housing unit size and number of appliances owned. In conclusion, research must take the latent nature of SES into account to uncover its total influence on REC. [ABSTRACT FROM AUTHOR]

Local and global climate change increases the ambient temperature of cities by several degrees with important consequences on energy consumption, health and the economy. Advanced urban mitigation technologies contribute to decrease the ambient temperature and counterbalance the impact of urban heat islands. The present paper analyses and presents in a comparative way the mitigation potential of the known mitigation technologies using performance data from about 220 real scale urban rehabilitation projects. The average and peak temperature drop of reflective technologies, greenery, evaporative systems, earth to air heat exchangers and their combinations is calculated and presented. The mitigation potential of the main systems like cool roofs, cool pavements, green roofs, urban trees, pools and ponds, sprinklers, fountains, and evaporative towers, is analysed. It is found that the potential of the main mitigation technologies is considerable and can counterbalance UHI effects partly or fully. The average peak temperature drop calculated for all projects is close to 2 K, while the corresponding decrease of the average ambient temperature is close to 0.74 K. Almost 31% of the analysed projects resulted in a peak temperature drop below 1 K, 62% below 2 K, 82% below 3 K and 90% below 4 K. [ABSTRACT FROM AUTHOR]

The term energy poverty is used to describe a situation of a household not able to satisfy socially and materially the required levels of its energy services. Energy and fuel poverty is an increasing problem in the European Union. Although the specific conditions vary from country to country the drivers defining fuel and energy poverty are similar in all Europe. This paper aims to present the state of the art regarding the energy demand and indoor environmental quality of low income households in Europe. The characteristics of this specific population group are presented including details on the specific energy consumption, the indoor comfort and finally the impact of the specific living conditions on the occupants' health. [ABSTRACT FROM AUTHOR]

Urban heat island and global warming increase significantly the ambient temperature. Higher temperatures have a serious impact on the electricity consumption of the building sector increasing considerably the peak and the total electricity demand. The present paper aims to collect, analyze and present in a comparative way existing studies investigating the impact of ambient temperature increase on electricity consumption. Analysis of eleven studies dealing with the impact of the ambient temperature on the peak electricity demand showed that for each degree of temperature increase, the increase of the peak electricity load varies between 0.45% and 4.6%. This corresponds to an additional electricity penalty of about 21 (±10.4) W per degree of temperature increase and per person. In parallel, analysis of fifteen studies examining the impact of ambient temperature on the total electricity consumption, showed that the actual increase of the electricity demand per degree of temperature increase varies between 0.5% and 8.5%. [ABSTRACT FROM AUTHOR]

The energy performance of buildings directive (EPBD) (91/2002/EU) opened the way for member states of European Union to create and apply a holistic approach on buildings’ energy performance. Taking into consideration the reduced ratio of new buildings, energy refurbishment of existing building stock appears as a nodal point. In particular, buildings in Greece accounts approximately 4 million, while 70% has been constructed before the implementation of the first Thermal Insulation Regulation (TIR), thus they do not have any insulation. So, there is an extremely high potential for energy conservation in Greek building stock. Therefore, an extensive field study was carried out in northern area of Greece in Thessaloniki, through a detailed questionnaire. The purpose of the research is to create an integrated thermal insulation scheme in order to succeed the highest mitigation of energy losses through building envelope. Retrofitting insulation solutions were evaluated and applied through various simulation scenarios with different levels of insulation thickness. [ABSTRACT FROM AUTHOR]

Surface temperature measurements carried out during summer period, at canyons' facades, pavements and street inside a deep urban canyon, in the center of Athens. At the same time experimental data of air temperature were collected through extensive monitoring in the center of the urban canyon. CFD simulations performed in order to calculate surface temperature in buildings' facades and at street level as well as air temperature inside the canyon. On the first part of this study comparison carried out between the measured and calculated values for a) surface temperature for the initial coating and b) the air temperature in the center of a deep street urban canyon. The calculated data have been thoroughly analyzed and used as well for the CFD model validation. The second task of this work was the calculation of the surface and air temperature, inside the deep urban canyon, by using a "cool" coating and the possible mitigation of the heat island effect in the specific urban area. The use of "cool" coatings, providing high reflectivity of solar radiation on the materials used on pavements and walls inside a canyon, estimated able to decrease surface temperature up to 7-8°C at ground level. The decrease on walls' surface temperature estimated close to 2-3°C. Ambient air temperature inside the urban street canyon may decrease up to 1°C. The reduction of absorbed solar radiation may lead to the energy consumption and thermal comfort conditions in cities and fight the increased heat island effect. [ABSTRACT FROM AUTHOR]

Highlights: [•] Very low indoor temperatures in low and very low income housing in Athens Greece. [•] Very low energy consumption because of the energy crisis. [•] Important environmental social and health problems associated to low indoor temperatures. [ABSTRACT FROM AUTHOR]

Abstract: The urban heat island (UHI) phenomenon is mainly caused by the differences in the thermal behaviour between urban and rural settlements that are associated with the thermal properties of urban materials, urban geometry, air pollution, and the anthropogenic heat released by the urban activities. The UHI has a serious impact on the energy consumption of buildings, increases smog production, while contributing to an increasing emission of pollutants from power plants, including sulfur dioxide, carbon monoxide, nitrous oxides and suspended particulates. This study presents the applicability of artificial neural networks (ANNs) and learning paradigms for UHI intensity prediction in Athens, Greece. The proposed model is tested using Elman, Feed-Forward and Cascade neural network architecture. The data of time, ambient temperature and global solar radiation are used to train and test the different models. The prediction accuracy is analyzed and evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Social, financial, energy and technical data from about 1110 households have been collected during 2004 in the major Athens area. The sample has been divided in seven income groups and a detailed analysis has been performed. Important conclusions have been drawn regarding the quality of households, the operational conditions and the energy spent per income group. Low income people are more likely to be living in old buildings with poor envelope conditions. The cost per person and unit area is much higher for the low income group for both heating and electricity. Fuel poverty is quite high, especially when the actual oil prices are considered. [Copyright &y& Elsevier]

Electrochromic glazing can involve substantial energy consumption in the building sector with their optical properties driven either by various occupant needs or environmental conditions. This paper presents comparison of ten different control strategies developed for such a glazing system in terms of specific energy consumption of a PASSYS test cell where the glazing was installed. The control strategies include scheduled ON–OFF controllers, a PID and advanced fuzzy controllers which were developed using experimental data. We used energy simulation to analyse the annual heating, cooling and lighting demands investigating the influence of each control strategy to the thermal behaviour of the building. [Copyright &y& Elsevier]

Abstract: The present paper deals with the energy performance, energy classification and rating and the global environmental quality of school buildings. A new energy classification technique based on intelligent clustering methodologies is proposed. Energy rating of school buildings provides specific information on their energy consumption and efficiency relative to the other buildings of similar nature and permits a better planning of interventions to improve its energy performance. The overall work reported in the present paper, is carried out in three phases. During the first phase energy consumption data have been collected through energy surveys performed in 320 schools in Greece. In the second phase an innovative energy rating scheme based on fuzzy clustering techniques has been developed, while in the third phase, 10 schools have been selected and detailed measurements of their energy efficiency and performance as well as of the global environmental quality have been performed using a specific experimental protocol. The proposed energy rating method has been applied while the main environmental and energy problems have been identified. The potential for energy and environmental improvements has been assessed. [Copyright &y& Elsevier]

This article deals with the energy performance of eight new and existing museum buildings located around Europe. Various energy efficiency and microclimate improvement measures have been adopted to reduce the energy consumption of the buildings and improve the comfort conditions. The investigation was implemented in two principal phases. During the first phase, energy simulation studies were performed in all buildings to evaluate the efficiency of the proposed measures and the various design possibilities. The energy consumption for heating, cooling, lighting and other electrical devices was calculated with and without the application of the proposed techniques and the corresponding energy conservation was estimated. Therefore, the proper measures from the energy point of view were adopted. During the second phase, measurements of the energy consumption were performed in the buildings after the finalization of the construction and the implementation of the proposed measures. The energy conservation was again calculated to evaluate the energy efficiency of the final construction. In addition to the energy aspect, the environmental impact of the final construction of the museums was investigated by calculating the reduction of the CO2 emissions due to the applied energy conservation techniques. Finally, the economic efficiency was examined by assessing the payback period of the adopted measures.The results of the present work show that the adaptation of energy conservation techniques in museums buildings can reduce significantly the energy consumption by respecting at the same time the requirements of the exhibition spaces and the comfort conditions of the visitors. [ABSTRACT FROM AUTHOR]

The archaeological museum of Delphi is one of the most visited museums in Greece with visitors ranging from about 150,000 to 300,000 per year. The building was retrofitted as a result of the Greek case study in the demonstration project ‘MUSEUMS—Energy Efficiency and Sustainability in Retrofitted and New Museum Buildings’ which was executed within the fifth Framework Programme of the European Commission DG TREN (Energie Programme). The retrofitting works aimed to integrate bioclimatic and sustainable measures in the existing exhibition halls, to minimize energy consumption and to improve comfort and exhibition quality. [ABSTRACT FROM AUTHOR]

This paper presents the results of a comparative study aiming to investigate the suitability of materials used in outdoor urban spaces in order to contribute to lower ambient temperatures and fight heat island effect. The study involved in total 93 commonly used pavement materials outdoors and was performed during the whole summer period of 2001. The thermal performance of the materials was measured in detail using mainly infrared thermography procedures.The collected data have been extensively analysed using statistical techniques. Comparative studies have been performed in order to identify the major advantages and disadvantages of the materials studied. Materials have been classified according to their thermal performance and physical properties into `cool'' and `warm'' materials. The impact of color, surface roughness and sizing has been analysed as well.The study can contribute to selection of more appropriate materials for outdoor urban applications, and thus assist to fight the heat island effect, decrease the electricity consumption of buildings and improve outdoor thermal comfort conditions. [Copyright &y& Elsevier]

A neural network approach is used in the present study for modelling and estimating the energy consumption time series for a residential building in Athens, using as inputs several climatic parameters.The hourly values of the energy consumption, for heating and cooling the building, are estimated for several years using feed forward backpropagation neural networks. Various neural network architectures are designed and trained for the output estimation, which is the building’s energy consumption. The results are tested with extensive sets of non-training measurements and it is found that they correspond well with the actual values.Furthermore, “multi-lag” output predictions of ambient air temperature and total solar radiation are used as inputs to the neural network models for modelling and predicting the future values of energy consumption with sufficient accuracy. [Copyright &y& Elsevier]

Assesses the impact of the urban climate on the energy consumption of buildings using climatic measurements from urban and suburban stations in Athens, Greece. Relative position of the measuring stations; Spatial and hourly distribution of the cooling degree hours in Athens for August 1996; Impact on the natural ventilation potential.

Urban overheating affects the energy, health, power, survivability and environmental quality of cities. We calculated the magnitude of overheating in Sydney, Australia, at close to 9 °C, which causes a cooling penalty of up to 16% and an increase in the indoor overheating levels of up to 56%. We developed and evaluated eight heat mitigation scenarios based on the use of reflective surfaces, additional greenery, an increase in the evapotranspiration rate and several combinations of these factors. We estimated that mitigation can decrease the peak ambient temperature by up to 2.9 °C, reduce the maximum annual cooling consumption by up to 1.5 TWh, decrease the CO2 emissions by as much as 1.21 MT CO 2 , reduce indoor overheating by up to 80%, decrease the heat-related morbidity by 1.07–1.49, and decrease the heat-related mortality anomaly by as much as 1.39 per 100,000 citizens. We estimated the associated water penalty range to be between 80 and 100 Gl/year or between 13 and 16.7% of the water consumption in Sydney. [ABSTRACT FROM AUTHOR]

Abstract: In the field of energy savings in buildings, the interest towards the school sector is deeply motivated: schools have standard energy demands and high levels of environmental comforts should be guaranteed. The University of Athens in collaboration with the School Authority of Greece undertook a complete program on energy classification and environmental quality of school buildings. Data on energy consumptions were gathered and analysed with the participation of 1100 schools from all the prefectures of Greece. The data have been provided by the school authority of the country (OSK), in collaboration with the management of each school building. With regards to the size of the building and the external climate variability (HDD-method) energy normalization techniques have been applied in order to homogenize the data set. An energy classification tool has been created through clustering techniques, using the collected data regarding the heating energy consumption and as a result five energy classes have been defined. To evaluate the potential energy conservation for each class, the typical characteristics of school buildings belonging to an energy class have to be identified. A new methodology based on the use of the principal components analysis (PCA) has been developed. The method allows to define in an accurate way the typical building of each energy class and thus to perform analysis on the potential energy savings for the specific group of school buildings. By reducing the dimensionality of the problem, a bi-dimensional graphic in the first two PCs coordinate system promotes the understanding of the correlation between the examined variables, as well as the determination of sub-groups of school buildings with similar characteristics. The typical school of seven variables sample is defined as the closest to the medians in the principal components’ coordinate system. [Copyright &y& Elsevier]

Museums are buildings of particular significance due to their function and their status. At the same time they are buildings in which the principles of energy conservation are rarely applied, sometimes without reason. It has been decided by the Hellenic Ministry of Culture to convert a medieval tower, built in the year 1344 as a fortress with 0.8–1.5 m thick walls and almost no windows, into a museum. The present paper discusses the difficulties that arise in the attempt to balance between the indoor climate conditions necessary to protect the exhibits and to provide comfortable conditions to the visitors, whilst respecting the aesthetics and the historical significance of the building. Furthermore, one needs to consider the difficult but necessary task of assessing factors such as the building’s shell’s thermal conductivity and capacity, the ventilation necessary as well as the indoor air movement, in order to determine the cooling loads. Finally, the challenge lies in designing and dimensioning an effective and efficient HVAC system, which should be as discrete as possible. The present paper aims to present the results of the study, to discuss the expected energy behaviour of the building and to comment on the options for introducing energy conservation techniques. [Copyright &y& Elsevier]

"Net-zero energy", a burning concept of the current world, has been being considered and applied on a building scale for the last few decades, however, there are significant advantages to moving to the community level. This study identifies the technological advancements of net-zero energy communities through in-depth literature review study. 23 case study settlements have been identified and analyzed based on their design methodology along with some practical applications around the globe. The focus of this work is on technologies and measures utilized for the reduction of energy consumption, minimization of greenhouse gas (GHG) emissions, and the generation of electrical and thermal energy by renewables. We identified different mitigation strategies adopted for outdoor heat sources, building adaptation techniques, and renewable energy technologies along with control strategies. The study reveals that all the settlements mainly focus on the onsite energy generation, while 17 settlements among them, additionally, consider various adaptation techniques that have significantly lessened the energy demand of the buildings. A few studies (4 settlements only) incorporate some mitigation strategies to mitigate the outdoor heat sources that enable to lower the ambient temperature along with diminishing the GHGs emissions as well as minimizing the energy demand of the community. In addition, the climate zones have significant impacts on selecting the building adaptation tools and measures. Alongside the energy balance, we have also epitomized the effects of various energy management and control strategies adopted for the smooth operation of energy. Finally, we shed light on the problems and challenges of existing net-zero energy settlements and make recommendations by considering the environment, energy, and economy towards achieving the net-zero energy purpose at the community level. [ABSTRACT FROM AUTHOR]

The recent global financial and economic crisis is responsible for the significant decrease of heating energy consumption, especially in low income population that mostly live in non-thermally-performing houses. The decrease of the residents’ income results in lower internal temperatures, hence lower thermal levels and lower indoor environmental quality, which are responsible for health problems and inadequate quality of life for the residents. This paper deals with the problem of energy poverty. The aim is to investigate whether the economic crisis, which affects the heating energy consumption and the indoor thermal quality, has consequences on the social and health problems in low income families of the Republic of Cyprus, during the winter season. To this aim, an extensive continuous monitoring study in terms of indoor air temperatures was carried out, for one year since December 2013 in 38 low income households in Limassol and Paphos, two of the main districts of the island after the capital of Nicosia. Additionally, questionnaires regarding energy, environmental, social, and health data were designed and collected from each household. Consequently, a cluster analysis, based on the monitoring data related to the first two months of 2014 and the survey’s responses, was performed. Poor households of Cyprus were found to live in low indoor thermal quality, i.e. their average indoor air temperatures (ranging from 16 to 19°C) are lower than the accepted limits of the comfort zone for the island (18–21°C in winter). However, the thermal comfort and health conditions were found between the “acceptable” and “good” levels for each cluster. Additionally, a strong correlation is detected between the average internal temperature of the dwellings and the average income of the selected families. Finally, the heating energy consumption was found to be lower than the country’s average for the clusters characterized by high and partial deprivation. [ABSTRACT FROM AUTHOR]

In recent years a steadily increasing interest has been noticed, concerning the development of advanced materials for both buildings and the urban environment. The aim of the present work is to examine the performance of inorganic coatings as a passive solar technique that contributes to buildings’ energy efficiency. A number of inorganic coatings are developed. The materials used for the coatings’ developed are characterized using XRD and DTA to verify their composition. Their optical properties, i.e. the solar reflectance and infrared emittance are then measured while the samples were also exposed to the outdoor environment for surface temperature measurements. Finally the energy efficiency of the specific coatings are evaluated in an insulated and non-insulated building using ESP-r modelling tool. [ABSTRACT FROM AUTHOR]