European residential buildings and empirical assessment of the Hellenic building stock,energy consumption,emissions and potential energy savings

The existing building stock in European countries accounts for over 40% of final energy consumption in the European Union (EU) member states, of which residential use represents 63% of total energy consumption in the buildings sector. Consequently, an increase of building energy performance can constitute an important instrument in the efforts to alleviate the EU energy import dependency (currently at about 48%) and comply with the Kyoto Protocol to reduce carbon dioxide emissions. This is also in accordance to the European Directive (EPBD 2002/91/EC) on the energy performance of buildings, which is currently under consideration in all EU member states. This paper presents an overview of the EU residential building stock and focuses on the Hellenic buildings. It elaborates the methodology used to determine the priorities for energy conservation measures (ECMs) in Hellenic residential buildings to reduce the environmental impact from CO₂ emissions, through the implementation of a realistic and effective national action plan. A major obstacle that had to overcome was the need to make suitable assumptions for missing detailed primary data. Accordingly, a qualitative and quantitative assessment of scattered national data resulted to a realistic assessment of the existing residential building stock and energy consumption. This is the first time that this kind of aggregate data is presented on a national level. Different energy conservation scenarios and their impact on the reduction of CO₂ emissions were evaluated. Accordingly, the most effective ECMs are the insulation of external walls (33–60% energy savings), weather proofing of openings (16–21%), the installation of double-glazed windows (14–20%), the regular maintenance of central heating boilers (10–12%), and the installation of solar collectors for sanitary hot water production (50–80%).     

A green roof model for building energy simulation programs

A physically based model of the energy balance of a vegetated rooftop has been developed and integrated into the EnergyPlus building energy simulation program. This green roof module allows the energy modeler to explore green roof design options including growing media thermal properties and depth, and vegetation characteristics such as plant type, height and leaf area index. The model has been tested successfully using observations from a monitored green roof in Florida. A preliminary set of parametric tests has been conducted on prototypical 4000 m² office buildings in Chicago IL and Houston TX. These tests focus on evaluating the role of growing media depth, irrigation, and vegetation density (leaf area index) on both natural gas and electricity consumption. Building energy consumption was found to vary significantly in response to variations in these parameters. Further, this response depended significantly on building location (climate). Hence, it is evident that the green roof simulation tool presented here can serve a valuable role in informing green roof design decisions.     

The retrofit of industrial air-conditioning system on energy efficiency and emission reduction

According to the requirement of Chinese National Policy of energy efficiency and emission reduction, optimized retrofit on the air-conditioning system of existing building is not only a measure to improve the building energy efficiency but also an important part to implement the emission reduction. This article put forward pertinent retrofit schemes after conducting analysis on the air-conditioning system of an industrial enterprise. With comparing the feasibility and the prospective effect of each retrofit scheme, the better one was determined.     

Energy consumption and the potential of energy savings in Hellenic office buildings used as bank branches—A case study

Energy performance of non-residential buildings and in particular of office buildings used as bank branches is very limited. This paper presents new data from 39 representative bank branches and results from a more in-depth analysis of information from energy audits in 11 typical bank branches throughout Greece. The data was used to derive practical energy benchmarks and assess various energy conservation measures. Accordingly, the average annual total energy consumption is 345 kWh/m². The breakdown of the different end-uses reveals that HVAC averages 48% of the final energy consumption, lighting averages 35% and other office and electronic equipment average 17%. The most effective energy conservation measures reach annual energy savings of 56 kWh/m² by regulating the indoor set point temperature, while the use of HF electronic ballasts and CFL lamps may save about 22 kWh/m² and 29 kWh/m² with and without the use of the external marquee sign, respectively.     

The selection of effective retrofit scenarios for panel houses in urban neighborhoods based on expected energy savings and increase in market value: The Vilnius case

Some of the problems associated with assessing the retrofit effectiveness of apartment buildings in urban areas are considered. The retrofit of houses should be followed by the amelioration of their surroundings. The priority order of districts to be renovated depends on the condition of the buildings in a district and on strategic urban development programmes. In order to determine the profitability of investments in housing retrofit, a number of retrofit scenarios should be developed. The authors of this paper offer a new approach to determining the retrofit effectiveness of houses based both on expected energy savings and the increase in market value of renovated buildings. In line with the proposed approach, retrofit scenarios for apartment buildings in Vilnius were developed, i.e. retrofit investment packages for various districts were prepared and arranged in the priority order for their application according to the method of geographical analysis suggested by the authors.     

The energy savings potential of using dynamic external louvers in an office building

This research is aimed at exploring the influence of external dynamic louvers on the energy consumption of an office building located in Abu Dhabi-UAE. The IES-VR software was used to predict the energy consumption of a representative office module in order to evaluate the overall energy performance of employing external louvers on the south, east and west oriented façades. The use of dynamic façades was compared to another simpler method of using light-sensor controlled light dimmers. The results show that the potential energy savings using light dimming strategy only was 24.4%, 24.45% and 25.19% for the south, east and west oriented façades, respectively. The proposed dynamic louvers system with light dimming strategy achieved energy savings of 34.02%, 28.57% and 30.31% for the south, east and west orientations, respectively. Detailed analysis of the results showed that the façade's optimal static angle was −20° for the south oriented façade and 20° for the east and west oriented façades. Using these fixed optimal angles resulted in slightly lower energy savings than that of the dynamic façades. This would seem to be a good tradeoff between savings in energy running cost and the investment required to install, operate and maintain a dynamic façades system.     

Characterization of the household electricity consumption in the EU, potential energy savings and specific policy recommendations

Although significant improvements in energy efficiency have been achieved in home appliances and lighting, the electricity consumption in the European Union household has increased by 2% per year during the past 10 years. Some reasons are associated with an increased degree of basic comfort and level of amenities and with the widespread utilisation of new types of loads. Wishing to increase the understanding of the energy consumption in the EU households for the different types of equipment including the consumers’ behaviour and comfort levels, and to identify demand trends, an energy monitoring campaign, was carried out in 12 geographically representative EU countries, accompanied by a lifestyle survey. From the measurements carried out it was concluded that Information Technologies and entertainment loads are key contributors to the power demand. In basically all types of loads there is wide range of performance levels in the models available in the market. Available technology, associated with responsible consumer behaviour, can reduce wasteful consumption. Based on a bottom up approach the European residential sector potential electricity savings that can be implemented by existing technologies and improved behaviour can reach 48%. The paper presents policy recommendations promoting market transformation and behavioural changes in the equipment selection and operation.     

绿色建筑技术在工程设计中的运用

近年来,绿色建筑已成为建筑行业的发展方向之一,它的出现符合环境,经济,能源现状,受到越来越多业内人士的重视。建筑对于环境的影响有目共睹,因此,减少建筑建设及运行过程中的能耗及污染也势在必行。绿色建筑的相关技术与日俱增,如何切合实际的运用,是建筑师们应关注的方面。正确积极的使用绿色建筑技术,对于建筑行业及整个社会,都将带来极大的益处。     

地震区某学校教学楼消能减震加固研究

以汶川地震后重灾区一学校教学楼为研究对象,利用消能减震技术,对消能减震加固方案进行了设计,以提高其抗震安全性,使之满足建筑抗震设计规范的要求,为今后类似的建筑结构加固设计提供有益的参考。     

Decoupling of building energy use and climate

Energy use intensity (EUI) and climate have a well documented correlation, which is generally applied in building energy management. Green buildings have sought to greatly reduce energy consumption and a number of examples are documented in the literature. A sample of high performance buildings constructed in a variety of global locations is analyzed here, and provides evidence that measures to reduce energy consumption have reduced EUI to the point where its correlation with heating degree days is no longer apparent. This result suggests that end-user behaviour is the next major hurdle in lowering the energy consumption of greener buildings.     

Data collection and analysis of the building stock and its energy performance—An example for Hellenic buildings

The process of building labeling and certification in accordance to the provisions of the European Directive on the Energy Performance of Buildings (EPBD) constitutes a unique opportunity for collecting information on the characteristics of the building stock and its energy performance on a national and European level. Thus, there is a need to handle data from a large stock of buildings and to be able to analyse information and extract practical trends and benchmarks. Stakeholders and technical managers who oversee a number of buildings experience similar needs in order to collect, organize and monitor the energy performance of a large pool of buildings. To facilitate these efforts, a common evaluation database and complimentary software for its exploitation have been developed in the frame of a European project.This paper presents an overview of the database and its available tools, and the main results from a case study on Hellenic buildings that reveals relevant characteristics. The Hellenic database included a sample of 250 buildings from different regions in Greece, with a breakdown that is representative of the national building stock. The main results focus on the buildings’ energy performance, thermal envelope characteristics and the exploitation of solar thermal energy.     

Calibrated building energy simulation and its application in a high-rise commercial building in Shanghai

The method of calibrated computer simulation is summarized on the basis of related literatures and guidelines. It is used to analyze the energy performance of a high-rise commercial building in Shanghai, China. DOE-2 energy model is built up with the detailed data of building and system that are collected on as-built drawings, specifications, operating records and site surveys. Model calibration is conducted on the comparison between simulation output and measured energy use. Energy model is adjusted until statistics indices are met in compliance to applicable standards and guidelines. Calibrated model is used in the performance analysis for energy conservation measures (ECMs) that are about to be implemented in the retrofitting project of the high-rise, including using variable speed chilled water pumps instead of constant variable speed ones, using free cooling during winter and mild seasons, decreasing lighting power densities. Energy saving performance is simulated and calculated to find out which ECM is the best option for the building.     

Evaluating the potential for energy savings on lighting by integrating fibre optics in buildings

The effective integration of an artificial lighting system and daylight in buildings occurs only when the artificial lighting system can be switched on or off as a function of daylight levels reaching the working surface of spaces. The paper considers fibre optics technology as a means of supplementing the daylight received at the rear of rooms and the subsequent integration of the total daylight received with a controlled artificial lighting system. Such an approach would contribute not only to energy savings but also to a reduction in environmental pollution. The evaluation took place using the climatic data from seven cities in Brazil and one in the UK. Results showed that by effectively integrating daylight from windows in buildings with the artificial lighting system, energy savings ranging from 17.7% to 92.0% could be achieved in the seven cities in Brazil and savings ranging from 10.8% to 44.0% could be achieved in the UK. By incorporating fibre optic technology into the system, the potential for energy savings on lighting was then found to range from 8.0% to 82.3% for the cities in Brazil and from 56.0% to 89.2% in the UK. For the city in the UK, it was further shown that there would be a reduction in carbon dioxide emission of 122 kg/m² of built area per year if daylight from windows were integrated with the artificial lighting system, and that this would increase to 138 kg/m² per year if fibre optics technology were to be installed.     

An object-oriented energy benchmark for the evaluation of the office building stock

Energy benchmarking is useful for understanding and enhancing building performance. The aim of this research is to develop an object-oriented energy benchmarking method for the evaluation of energy performance in buildings. Statistical analysis of the four-year monitored energy consumption data for office buildings was conducted. The results show that the energy use intensity follows the lognormal distribution with the Shapiro–Wilk normality test. Based on the lognormal distribution, the energy rating system for office buildings has been established. An object-oriented energy use intensity quota determination model has been developed. This research provides practical tools that enable decision-makers to evaluate a building's energy performance and determine the energy benchmark.     

推陈出新———以福建省建筑设计研究院旧楼节能改造为例

城市的发展是一个不断更新和变化的动态过程。在这种新陈代谢的过程中,如何在已有的限制条件下,以环保、经济、科学、节能减排的理念,为旧建筑注人新的生命力,完成旧建筑的重生成为近几年来关注的热点问题。本文就以福建省建筑设计研究院旧楼节能改造为例,为同类型办公楼推陈出新提供参考。     

既有办公建筑节能改造示范及能耗监测系统研究

本文对某办公大楼示范的节能改造措施进行探讨,通过建筑节能改造前后的能耗情况进行对比分析,明确了适宜的节能改造方向,并提出利用建筑能耗监测系统对改造后的建筑能耗进行分析,有利于用能管理。     

建筑节能模拟程序中的绿色屋面模型

将一个关于植物种植屋顶能量平衡的物理方程嵌入到EnergyPlus建筑能量模拟程序中。该绿色屋面模型可以考虑到持续增加的传热性能和深度,同时可考虑植物特性、类型、高度和绿叶覆盖率。通过观察佛罗里达一个被监控的绿色屋顶证实了此模型的有效性。在芝加哥和休斯顿的4000m2办公楼中进行了参数试验。这些试验集中研究了植物的深度、灌溉程度、密度(绿叶覆盖面积)在天然气和电消耗量上的作用。这些参数对建筑耗能量的影响很明显。此外,建筑物的位置(气候)对其耗能作用的影响也很大。因此,这个绿色屋面模拟工具对环保屋面的设计非常有用。     

A methodology for assessing the energy performance of large scale building stocks and possible applications

From energy statistics (primary energy consumption) and a few Census data (residential buildings floor area) the average specific primary energy use (kWh/m²) of a territorial (Regional or National) building stock may be easily evaluated. However, can we achieve a deeper insight on this building stock using basically the same data bases? This is the question which this paper is aiming at, and the results is an analytical methodology to determine the Statistical Distribution Of residential Buildings according to primary Energy consumption for heating purposes (E-SDOB) at a Regional or National scale. This tool may allow the legislator to define a performance scale for building energy certification, to introduce mandatory measures and incentives for building energy retrofits, to evaluate the potential of new technologies, etc. The main source of data required for determining E-SDOB is still the National Census, but it has to be integrated by energy standards and laws, literature and a few data taken from the authors’ experience and in situ analysis. The results obtained have been compared with those derived from two Italian Regional (Piedmont and Lombardy) energy statistics, with excellent agreement.     

Developing a new library of materials and structural elements for the simulative evaluation of buildings’ energy performance

Contemporary building energy simulation programs are not only used by researchers but also are common tools in the hands of engineers and architects. Most of them are using databases of materials and structural elements, with characteristics originating from the country or the broader region where the specific program was developed. Thus, often the particularities met in other countries are not considered. Such a database of materials and constructions systematically used in the Greek building sector was developed for use with the simulation program EnergyPlus, which has become quite popular over the last years. In order to determine the applicability of the database, the energy behaviour of a typical multistory, multifamily building was simulated, having the exact materials and structural elements and patterns used in Greece. Furthermore, different thicknesses of insulation were simulated, corresponding to local climatic conditions and, even more important, to different dates of the building's construction. The results are presented and discussed in this paper.     

Comparison between detailed model simulation and artificial neural network for forecasting building energy consumption

There are several ways to attempt to model a building and its heat gains from external sources as well as internal ones in order to evaluate a proper operation, audit retrofit actions, and forecast energy consumption. Different techniques, varying from simple regression to models that are based on physical principles, can be used for simulation. A frequent hypothesis for all these models is that the input variables should be based on realistic data when they are available, otherwise the evaluation of energy consumption might be highly under or over estimated.In this paper, a comparison is made between a simple model based on artificial neural network (ANN) and a model that is based on physical principles (EnergyPlus) as an auditing and predicting tool in order to forecast building energy consumption. The Administration Building of the University of São Paulo is used as a case study. The building energy consumption profiles are collected as well as the campus meteorological data.Results show that both models are suitable for energy consumption forecast. Additionally, a parametric analysis is carried out for the considered building on EnergyPlus in order to evaluate the influence of several parameters such as the building profile occupation and weather data on such forecasting.