Using national input/output data for embodied energy analysis of individual residential buildings

Embodied energy (EE) analysis has become an important area of energy research, in attempting to trace the direct and indirect energy requirements of products and services throughout their supply chain. Typically, input-output (I-O) models have been used to calculate EE because they are considered to be comprehensive in their analysis. However, a major deficiency of using I-O models is that they have inherent errors and therefore cannot be reliably applied to individual cases. Thus, there is a need for the ability to disaggregate an I-O model into its most important ‘energy paths’, for the purpose of integrating case-specific data. This paper presents a new hybrid method for conducting EE analyses for individual buildings, which retains the completeness of the I-O model. This new method is demonstrated by application to an Australian residential building. Only 52% of the energy paths derived from the I-O model were substituted using case-specific data. This indicates that previous system boundaries for EE studies of individual residential buildings are less than optimal. It is envisaged that the proposed method will provide construction professionals with more accurate and reliable data for conducting life cycle energy analysis of buildings. Furthermore, by analysing the unmodified energy paths, further data collection can be prioritized effectively.     

Life-cycle energy analysis of buildings: a case study

Energy use is a widely used measure of the environmental impact of buildings. Recent studies have highlighted the importance of both the operational and embodied energy attributable to buildings over their lifetime. The method of assessing lifetime building energy is known as life-cycle energy analysis. With Kyoto target obligations necessitating the quantification of greenhouse gas emissions at the national level, it seems increasingly probable that analyses of this kind will increase in use. If conducted in primary energy terms, such analyses directly reflect greenhouse gas emissions, except for a few processes which involve significant non-energy related emissions such as cement manufacture. A Life-Cycle Assessment would include these issues, as well as other environmental parameters, though probably with a corresponding decrease in system boundary completeness. This paper briefly explains some of the theoretical issues associated with life-cycle energy analysis and then uses an Australian based case study to demonstrate its use in evaluating alternative design strategies for an energy efficient residential building. For example, it was found that the addition of higher levels of insulation in Australia paid back its initial embodied energy in life-cycle energy terms in around 12 years. However, the saving represented less than 6% of the total embodied energy and operational energy of the building over a 100-year life cycle. This indicates that there may be other strategies worth pursuing before additional insulation. Energy efficiency and other environmental strategies should be prioritized on a life-cycle basis.

La consommation d'énergie est un paramètre très utilisé lorsque l'on veut mesurer l'impact des bâtiments sur l'environnement. Des études conduites récemment ont mis en lumière l'importance de l'énergie opérationnelle et celle de l'énergie intrinsèque dégagées par les bâtiments pendant leur durée de vie. L'analyse énergétique des bâtiments pendant leur cycle de vie est une méthode d'évaluation de l'énergie d'un bâtiment pendant sa durée de vie. Pour respecter les objectifs de la Conférence de Kyoto, il faut quantifier les émissions de gaz de serre au niveau national; il semble donc de plus en plus probable que la pratique de ces analyses va aller en augmentant. Si elles portent sur l'énergie primaire, ces analyses rendront parfaitement compte des émissions de gaz à effets de serre, sauf pour quelques procédés industriels, comme la fabrication du ciment, où les émissions de ces gaz ne sont pas liées à l'énergie. Toute évaluation du cycle de vie doit tenir compte de ces questions mais aussi d'autres paramètres environnementaux, mais avec, sans doute, une moindre netteté des limites des systèmes. Le présente communication expose brièvement quelques uns des problèmes théoriques liés aux analyses ènergétiques sur le cycle de vie et s'appuie sur une étude de cas australienne pour démontrer son utilitè à évaluer d'autres stratégies de conception de bâtiments à usage d'habitation à faible consommation d'énergie. On a constaté, par exemple, qu'en Australie le fait d'ajouter des niveaux d'isolation remboursait en 12 ans environ l'énergie intrinsèque initiale en terme d'énergie sur le cycle de vie. Toutefois, les economies répresentaient moins de 6% de l'énergie intrinsèque totale et de l'energie opérationnelle du bâtiment sur un cycle de vie de 100 ans. Cela veut dire qu'il serait peut etre intéressant d'envisager d'autres stratégies avant d'augmenter l'isolation. On devrait donner priorité à l'efficacité énergétique et à d'autres stratégies environnementales sur la base du cycle de vie.     

Life-cycle energy analysis of buildings: a case study

Energy use is a widely used measure of the environmental impact of buildings. Recent studies have highlighted the importance of both the operational and embodied energy attributable to buildings over their lifetime. The method of assessing lifetime building energy is known as life-cycle energy analysis. With Kyoto target obligations necessitating the quantification of greenhouse gas emissions at the national level, it seems increasingly probable that analyses of this kind will increase in use. If conducted in primary energy terms, such analyses directly reflect greenhouse gas emissions, except for a few processes which involve significant non-energy related emissions such as cement manufacture. A Life-Cycle Assessment would include these issues, as well as other environmental parameters, though probably with a corresponding decrease in system boundary completeness. This paper briefly explains some of the theoretical issues associated with life-cycle energy analysis and then uses an Australian based case study to demonstrate its use in evaluating alternative design strategies for an energy efficient residential building. For example, it was found that the addition of higher levels of insulation in Australia paid back its initial embodied energy in life-cycle energy terms in around 12 years. However, the saving represented less than 6% of the total embodied energy and operational energy of the building over a 100-year life cycle. This indicates that there may be other strategies worth pursuing before additional insulation. Energy efficiency and other environmental strategies should be prioritized on a life-cycle basis. La consommation d'energie est un parametre tres utilise lorsque l'on veut mesurer l'impact des batiments sur l'environnement. Des etudes conduites recemment ont mis en lumiere l'importance de l'energie operationnelle et celle de l'energie intrinseque degagees par les batiments pendant leur duree de vie. L'analyse energetique des batiments pendant leur cycle de vie est une methode d'evaluation de l'energie d'un batiment pendant sa duree de vie. Pour respecter les objectifs de la Conference de Kyoto, il faut quantifier les emissions de gaz de serre au niveau national; il semble donc de plus en plus probable que la pratique de ces analyses va aller en augmentant. Si elles portent sur l'energie primaire, ces analyses rendront parfaitement compte des emissions de gaz a effets de serre, sauf pour quelques procedes industriels, comme la fabrication du ciment, ou les emissions de ces gaz ne sont pas liees a l'energie. Toute evaluation du cycle de vie doit tenir compte de ces questions mais aussi d'autres parametres environnementaux, mais avec, sans doute, une moindre nettete des limites des systemes. Le presente communication expose brievement quelques uns des problemes theoriques lies aux analyses energetiques sur le cycle de vie et s'appuie sur une etude de cas australienne pour demontrer son utilite a evaluer d'autres strategies de conception de batiments a usage d'habitation a faible consommation d'energie. On a constate, par exemple, qu'en Australie le fait d'ajouter des niveaux d'isolation remboursait en 12 ans environ l'energie intrinseque initiale en terme d'energie sur le cycle de vie. Toutefois, les economies representaient moins de 6% de l'energie intrinseque totale et de l'energie operationnelle du batiment sur un cycle de vie de 100 ans. Cela veut dire qu'il serait peut etre interessant d'envisager d'autres strategies avant d'augmenter l'isolation. On devrait donner priorite a l'efficacite energetique et a d'autres strategies environnementales sur la base du cycle de vie.     

Life cycle of buildings,demolition and recycling potential: A case study in Turin,Italy

One of the most challenging issues presently facing policymakers and public administrators in Italy concerns what to do with waste materials from building dismantling activities and to understand whether, and to what extent, the ever-increasing quantity of demolition waste can replace virgin materials. The paper presents the results from a research programme that was focused on the life cycle assessment (LCA) of a residential building, located in Turin, which was demolished in 2004 by controlled blasting. A detailed LCA model was set-up, based on field measured data from an urban area under demolition and re-design, paying attention to the end-of-life phase and supplying actual data on demolition and rubble recycling. The results have demonstrated that, while building waste recycling is economically feasible and profitable, it is also sustainable from the energetic and environmental point of view. Compared to the environmental burdens associated with the materials embodied in the building shell, the recycling potential is 29% and 18% in terms of life cycle energy and greenhouse emissions, respectively. The recycling potential of the main building materials was made available in order to address future demolition projects and supply basic knowledge in the design for dismantling field.     

A life-cycle energy analysis of building materials in the Negev desert

Environmental quality has become increasingly affected by the built environment—as ultimately, buildings are responsible for the bulk of energy consumption and resultant atmospheric emissions in many countries. In recognizing this trend, research into building energy-efficiency has focused mainly on the energy required for a building's ongoing use, while the energy “embodied” in its production is often overlooked. Such an approach has led in recent years to strategies which improve a building's thermal performance, but which rely on high embodied-energy (EE) materials and products. Although assessment methods and databases have developed in recent years, the actual EE intensity for a given material may be highly dependent on local technologies and transportation distances. The objective of this study is to identify building materials which may optimize a building's energy requirements over its entire life cycle, by analyzing both embodied and operational energy consumption in a climatically responsive building in the Negev desert region of southern Israel—comparing its actual material composition with a number of possible alternatives. It was found that the embodied energy of the building accounts for some 60% of the overall life-cycle energy consumption, which could be reduced significantly by using “alternative” wall infill materials. The cumulative energy saved over a 50-year life cycle by this material substitution is on the order of 20%. While the studied wall systems (mass, insulation and finish materials) represent a significant portion of the initial EE of the building, the concrete structure (columns, beams, floor and ceiling slabs) on average constitutes about 50% of the building's pre-use phase energy.     

Investigation of energy performance of newly built low-energy buildings in Sweden

Energy use in the built environment represents a large part of total energy use in Sweden and is one important sector where energy conservation needs to be significantly improved in order to meet the national implementation of the European goals. One key question that needs to be investigated in relation to these goals is the performance and implementation of passive or low-energy houses. This paper presents results and an evaluation of a newly built house in an area with passive houses in Linköping, Sweden. Nine passive houses were built with the aim to be energy efficient, with an annual space heating demand of 21 kWh/m², and at the same time to have the same visual appearance as any other building in the surrounding area.This study evaluates the energy performance of a residential area with low-energy buildings based on Building Energy Simulation (BES) (IDA ICE 4), and measurements from the real object. Both annual and hourly validation is performed using room by room modeling and internal heat gains. A novel approach to internal heat gain modeling is presented using time-use data (TUD). The results show possible improvements in the design, the building envelope and in the heating control.     

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.     

Automatic generation of energy conservation measures in buildings using genetic algorithms

Building energy simulations are key to studying energy efficiency in buildings. The state-of-the art building energy simulation tools requires a high level of multi disciplinary domain expertise from the user and many technical data inputs that curb the usability of such programs. In this paper an IT tool is presented, which has the capability of predicting a building's energy utilization configuration based on the reported annual energy and a few non-technical inputs from the user; and correspondingly generates cost effective energy conservation measures for the intended savings.The approach first identifies the system variables that are critical to a building's energy consumption and searches for the combination of these parameters that would give rise to the annual energy consumption as reported by the facility. Genetic algorithms are utilized to generate this database. A statistical fit is formulated between the system variables and the annual energy consumption from the database. Using this correlation, system configuration for the target energy efficiency is determined with corresponding energy conservation measures. A cost analysis is carried out to prescribe the most cost effective energy conservation measures. Competency of the tool is demonstrated in the paper through case studies on three geographies with different climate conditions.     

Evaluation of green buildings in Sweden

This paper reports on experiences from the Swedish participation in Green Building Challenge '98 and ongoing similar work in Sweden. It argues against very simplified environmental assessment methods and recommends, as far as possible, calculation of environmental effects caused by buildings during their life cycle. Participation in the development of the GBC tool provided a broad view of the issues, clarified different opinions in a new field and provided additional stimulation while developing our national assessment methodology, EcoEffect. The environmental assessment of buildings is discussed in relation to the strength and weaknesses of the GBC system. The design and characteristics of 'green buildings' in Sweden is addressed, including ten poster presentations and two case studies presented at GBC '98. Cet article rend compte des experiences liees a la participation de la Suede au projet Green Building Challenge '98 et a des travaux similaires en cours d'execution en Suede. Il procede a l'analyse critique de methodes d'evaluation de l'environnement tres simplifiees et recommande que, dans la mesure du possible, on calcule les incidences sur l'environnement imputables aux batiments pendant leur cycle de vie. La contribution aux travaux de developpement du GBC Tool a permis d'arriver a une vision plus large des problemes, de faire la lumiere sur des opinions differentes dans un domaine nouveau et est a l'origine d'une stimulation nouvelle tout en developpant notre methodologie d'evaluation nationale, EcoEffect. L'evaluation environnementale de batiments est passee en revue sur fond de points forts et de points faibles du systeme GBC. L'article etudie la conception et les caracteristiques des 'batiments verts' en Suede; ce sujet fait egalement l'objet de 10 presentations par affiches et de 2 etudes de cas presentees a la conference GBC '98.     

Building typologies as a tool for assessing the energy performance of residential buildings - A case study for the Hellenic building stock

Successful strategies towards minimizing the energy consumption and greenhouse gas emissions attributed to the building sector require knowledge on the energy-related characteristics of the existing building stock. Despite the numerous studies on energy conservation applications in buildings, current knowledge on the energy-related characteristics of the building stock still remains limited. Building typologies can be a useful instrument to facilitate the energy performance assessment of a building stock. This work is based on a harmonised structure for European building typologies (TABULA) developed for residential buildings, but the methodology may be extended to the tertiary sector as well. National typologies are sets of model buildings with characteristic energy-related properties representative of a country's building stock. The model buildings are used as a showcase for demonstrating the energy performance and the potential energy savings from typical and advanced energy conservation measures (ECMs) on the thermal envelope and the heat supply system. The proposed Hellenic residential building typology is presented for the first time along with an assessment of various ECMs that are used for an estimate of the energy performance of building stock in Greece in an effort to meet the 9% indicative national energy savings target by 2016.     

Application of energy rating methods to the existing building stock: Analysis of some residential buildings in Turin

The objective of this work is to contribute to the recent standardisation activity, finalized to apply the Energy Performance of Buildings Directive (EPBD). Through the energy assessment of some residential buildings in Turin (Italy), the work investigates the application of the calculation methods that have been specified in the recent European standard for the so-called “standard energy rating”. A comparison of the “calculated energy rating” with the “measured energy rating” is used to investigate the effect of user behaviour and weather conditions. Moreover, in order to draft the energy certificate and make an appropriate classification, the last part of the work investigates the way to find energy reference values of the building stock, through the study of the correlation between the input and the output data of an energy rating and the comparison of the analysed buildings.     

Life cycle assessment of building materials: Comparative analysis of energy and environmental impacts and evaluation of the eco-efficiency improvement potential

The building industry uses great quantities of raw materials that also involve high energy consumption. Choosing materials with high content in embodied energy entails an initial high level of energy consumption in the building production stage but also determines future energy consumption in order to fulfil heating, ventilation and air conditioning demands.     

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%).     

Longitudinal prediction of the operational energy use of buildings

Thus far most studies of operational energy use of buildings fail to take a longitudinal view, or in other words, do not take into account how operational energy use changes during the lifetime of a building. However, such a view is important when predicting the impact of climate change, or for long term energy accounting purposes. This article presents an approach to deliver a longitudinal prediction of operational energy use. The work is based on the review of deterioration in thermal performance, building maintenance effects, and future climate change. The key issues are to estimate the service life expectancy and thermal performance degradation of building components while building maintenance and changing weather conditions are considered at the same time. Two examples are presented to demonstrate the application of the deterministic and stochastic approaches, respectively. The work concludes that longitudinal prediction of operational energy use is feasible, but the prediction will depend largely on the availability of extensive and reliable monitoring data. This premise is not met in most current buildings.     

The development of reference values for energy certification of buildings in Lithuania

The paper deals with the experience in the field of arrangement of the building certification system in Lithuania. The arranged document provides the energy consumption in a building to estimate according to the calculation results, including heat losses through the building envelope elements, due to the ventilation, air infiltration and domestic hot water. The reference U-values for the building elements representing the best 50% of the building stock are derived. The changes in the energy consumption and reference values in regard with building renovation development are discussed.     

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.     

Structure optimization of energy supply systems in tertiary sector buildings

Trigeneration systems, also known as Combined Heat, Cooling and Power (CHCP) systems, are interesting alternatives to supply different energy services in urban districts and in large buildings, particularly in warm areas such as Mediterranean countries. These systems can provide substantial benefits from economic, energetic, and environmental viewpoints, since the cogenerated heat can be used for heating in winter as well as cooling in summer with an absorption refrigerator. This paper develops an optimization model using Mixed Integer Linear Programming (MILP) to determine the type, number and capacity of equipment in CHCP systems installed in the tertiary sector as well as to establish the optimal operation mode for the different plant components on an hour-by-hour basis throughout the year. The objective function to be minimized is the annual total cost. The optimization model considers the legal constraints imposed to feed the surplus autogenerated electricity into the grid at a regulated feed-in tariff. The optimization model is applied to design a system providing energy services for a hospital located in the city of Zaragoza (Spain). The effects of the financial market conditions and energy prices in the optimal structure of the system are analyzed.     

Improving the energy performance of the built environment: The potential of virtual collaborative life cycle tools

Advances in information and communication technologies [ICTs] offer the opportunity to improve the way energy profiling tools and techniques are used to measure and inform the energy performance of buildings throughout their life cycle. The exploitation of this potential is one of the goals of a current EU FP7 funded project, entitled “IntUBE — Intelligent Use of Buildings' Energy Information”. The overall aim of the project is to improve the energy performance of new and existing buildings via the intelligent use of buildings' energy information. The main aim the energy profiling research being conducted as part of the IntUBE project is to contribute to the development of virtual collaborative ‘life cycle’ building tools to support energy efficient building design, operation and retrofit. In order to illustrate how this may be achieved this paper defines the functions of energy simulations within the IntUBE system, outlines the systems architecture necessary to those functions and presents a case study illustrating some of the functionality under development.