Using Display Energy Certificates to quantify schools' energy consumption

The UK non-domestic sector accounts for 2 million buildings and 19% of national CO₂ emissions, representing a significant opportunity for emission reductions. However, substantial improvement of the stock requires a greater understanding of current energy performance characteristics. This paper explores energy consumption in English schools, using data from the Display Energy Certificates (DECs) database. DECs are a key step in understanding the non-domestic stock, incorporating national-scale statistical data, covering bottom-up details of the individual buildings. Significant variations in emissions between primary and secondary schools and academies exist, primarily caused by large differences in electricity consumption. Considering pupil numbers is shown to accentuate the differences, revealing a 47% rise in CO₂ emissions per pupil from primary to secondary schools, and a further increase between secondary schools and academies. The extent to which building characteristics, including location, heating, ventilation and air-conditioning (HVAC) and size, influence performance has also been evaluated. Location, HVAC and school density are shown to correlate with variations in energy use. Finally, a comparison of current school performance against past data reveals considerable reductions in fossil-thermal energy consumption over the last decade. However, this has been offset by a significant increase in electricity consumption, resulting in rising typical emissions across the school types.

Le secteur non domestique britannique représente 2 millions de bâtiments et 19% des émissions de CO₂ du pays, ce qui constitue une importante opportunité de réduction des émissions. Cependant, une amélioration substantielle du parc exige une plus grande compréhension des caractéristiques actuelles des performances énergétiques. Cet article examine la consommation d'énergie dans les écoles anglaises, en utilisant les données provenant de la base de données des Display Energy Certificates (DEC – Certificats de Performance Energétique à afficher). Les certificats DEC sont une étape clé pour mieux connaître le parc non domestique, intégrant des données statistiques à l'échelle nationale et couvrant en détail selon une approche ascendante les différents bâtiments. D'importantes variations des émissions entre les écoles primaires, les écoles secondaires et les académies existent, principalement dues à de grandes différences dans la consommation électrique. Il est démontré que la prise en compte du nombre d'élèves accentue les différences, révélant une hausse de 47% des émissions de CO₂ par élève entre les écoles primaires et secondaires, une hausse supplémentaire intervenant entre les écoles secondaires et les académies. A également été évalué le degré d'influence sur les performances des caractéristiques des bâtiments, au nombre desquelles l'emplacement, le chauffage, la ventilation mécanique et la climatisation (CVCA), ainsi que la taille. Il est démontré que l'emplacement, la CVCA et la densité des écoles sont en corrélation avec les variations de la consommation d'énergie. Enfin, une comparaison des performances actuelles des écoles par rapport aux données passées révèle des réductions considérables de la consommation d'énergie thermique fossile au cours de la dernière décennie. Cependant, ceci a été contrebalancé par une augmentation importante de la consommation d'électricité, qui s'est traduite par une hausse des émissions moyennes sur l'ensemble des types d'écoles.

indicateurs de référence, parc immobilier, émissions de CO₂, Certificats de Performance Energétique (DEC), consommation d'énergie, écoles     

Using Display Energy Certificates to quantify public sector office energy consumption

The influence of internal and external characteristics on energy use in the public sector office stock in England and Wales is explored using a database of 2600 Display Energy Certificates (DECs) combined with other sources of disaggregated office information. The DEC office benchmarks are shown to match the median fossil thermal and electrical consumptions well. Analyses of heating, ventilation and air-conditioning (HVAC), size, occupancy density, building age, location and rateable value are considered. While newer offices are shown to have lower typical fossil-thermal consumption than older offices, this is counterbalanced by higher electrical consumption, resulting in higher typical CO₂ emissions. This has implications for the UK's emissions reduction targets for 2050, indicating that while building regulations that focus on thermal performance have been successful, a focus on electrical consumption (both regulated and unregulated) is key. The results are also compared with existing benchmarks for all UK offices, splitting the sample into four generic types, and compared with a similar smaller study of private offices. This indicates that public offices typically used less energy than the general benchmarks had previously predicted, particularly for prestige offices.     

A review of bottom-up building stock models for energy consumption in the residential sector

Efficient and rational implementation of building stock CO₂ emission reduction strategies and policies requires the application of comprehensive building stock models that have the ability to: (a) estimate the baseline energy demand of the existing building stock, (b) explore the technical and economic effects of different CO₂ emission reduction strategies over time, including the impact of new technologies, and (c) to identify the effect of emission reduction strategies on indoor environmental quality.     

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%).     

Towards a universal energy efficiency index for buildings

The growing worldwide demand for energy is basically satisfied through natural resources such as oil or natural gas generally acknowledged as being responsible for climate change through greenhouse gas emissions. The building sector accumulates approximately a third of the final energy consumption. Consequently, the improvement of the energy efficiency in buildings has become an essential instrument in the energy policies to ensure the energy supply in the mid to long term, and to meet the targets stated in the Kyoto Protocol. During the last decade and being sensitive to this fact, many national governments and international organizations have developed new regulations to achieve those targets. One of these regulations is the European Energy Performance of Buildings Directive but, to date this certification does not follow a standard procedure which is universally accepted.This paper aims to contribute to this standardization, proposing an energy efficiency index for buildings that relates the energy consumption within a building to reference consumption. The proposed energy index can be obtained in a simple manner by combination standard measurements of energy consumption, simulation and public databases. Furthermore, the index is upgradable whenever new data are available.     

Evaluation of BIM energy performance and CO2 emissions assessment tools: a case study in warm weather

ABSTRACT

The EU members have adopted regulations and official methods for evaluating the energy performance in buildings. Most of these methods are applied at the end of the project phase, with few opportunities to correct erroneous design decisions when the desired building energy performance is not achieved. It is demonstrated that there is no European standard for sustainability and that the decision-making process during the development of a building project is compromised by the methodologies and some concepts, as thermal inertia, are withdrawn. Currently, the industry has been developing alternative tools for evaluating energy performance and CO₂ emissions in buildings over their entire life cycle. These software programs, which belong to the BIM environment, use databases and make simplifications adapted to the stage of design when the software can be applied. The main objective of this paper is to evaluate the accuracy of this software and how the databases and simplifications influence the decision-making process in building design. Calculation examples are carried out with various tools and compared to real building performance data. The results demonstrate that, as with the official methods, the tools influence the results and therefore condition, sometimes wrongly, the decision-making process to produce better buildings.     

Improving energy benchmarking with self-reported data

Energy benchmarking for buildings has become increasingly important in government policy and industry practice for energy efficiency. The questions of how energy benchmarking is currently conducted, and how it might be improved using rapidly growing quantities of self-reported data, are examined. A case study of commercial office buildings in New York City demonstrates how the rapid growth in self-reported data presents both new opportunities and challenges for energy benchmarking for buildings. A critique is presented for the scoring methodology and data sources for Energy Star, one of the largest and most successful benchmarking certification schemes. Findings from recent studies are examined to illustrate how this certification currently works in the marketplace. Self-reported building energy data are rapidly growing in Portfolio Manager (the user interface to Energy Star) due to mandatory energy benchmarking laws, and can be used to improve Energy Star's current scoring methods. These self-reported data are tested and improved for analysis by applying theories and methods of data quality developed in computer science, statistics and data management. These new data constitute a critical building block for the development of energy efficiency policies, and will affect how government, consultants, and owners measure and compare building energy use.     

Analysis of energy and carbon flows in the future Norwegian dwelling stock

A dynamic analysis of future energy and carbon flows (2000–2050) is performed on the aggregated residential building stock in Norway. The basis for the analysis is a dynamic material flow analysis of floor areas and the main building materials. By adding energy intensity assumptions for space heating, water heating, domestic electrical appliances and embodied energy in construction materials, the future corresponding delivered energy demand is calculated. This forms the basis for life cycle estimation of the future direct and indirect greenhouse gas (GHG) emissions. The predicted demand for delivered energy in 2025 will increase by 24.0% and 12.5% above those for 2000 and 2010, respectively, and then remain stable towards 2050. Energy savings per unit of floor area are counterbalanced by growth in the building stock. The very high influence of energy technology assumptions within the electricity generation market is demonstrated, along with the large differences between using attributional and consequential life cycle assessment principles in the calculation of future emissions. Future electricity demand met by marginal power generation technologies in the European market will yield substantially higher GHG emissions. The simulations demonstrate the policy, strategy, and practical challenges in achieving significant long-term energy and GHG emission reductions from the residential building stock in a country with a rapidly growing population.

Une analyse dynamique des flux futurs d'énergie et de carbone (2000-2050) est réalisée en Norvège sur l'ensemble du parc de logements (immeubles résidentiels). La base de l'analyse consiste en une analyse dynamique des flux de matières des surfaces au sol et des principaux matériaux de construction. En ajoutant des hypothèses relatives à l'intensité énergétique concernant le chauffage d'ambiance, la production d'eau chaude, les appareils électroménagers et l'énergie intrinsèque des matériaux de construction, la demande future correspondante en énergie livrée est calculée. Ceci constitue la base pour l'estimation du cycle de vie des futures émissions directes et indirectes de gaz à effet de serre (GES). La demande prévue d'énergie livrée en 2025 sera en augmentation de 24,0% et de 12,5%, respectivement, par rapport à la demande de 2000 et à celle de 2010, puis demeurera stable vers 2050. Les économies d'énergie par unité de surface au sol sont contrebalancées par la croissance du parc bâti. Démonstration est faite de la très forte influence des hypothèses relatives aux technologies énergétiques dans le marché de la production d'électricité, ainsi que des grandes différences existant entre le fait d'utiliser, pour le calcul des émissions futures, les principes d'une analyse attributionnelle et ceux d'une analyse conséquentielle du cycle de vie. La demande future d'électricité satisfaite par les technologies marginales de production d'électricité dans le marché européen générera des émissions de gaz à effet de serre sensiblement plus élevées. Les simulations montrent les défis qui se posent en termes de politique, de stratégie et sur le plan pratique, pour réaliser des réductions à long terme importantes de la consommation énergétique et des émissions de GES provenant du parc bâti résidentiel.

secteur du bâtiment?parc bâti?bâtiments?réduction du CO₂?consommation énergétique?émissions de gaz à effet de serre?analyse des flux de matières?atténuation?Norvège     

Saturation, energy consumption, CO2 emission and energy efficiency from urban and rural households appliances in Mexico

Energy usage and energy efficiency are of increasing concern in Mexico, electricity generation principally depends upon fossil fuels. On one hand, the stocks of these fuels have been confirmed to be critically limited. On the other hand, in process of electricity generation by means of these fuels, a number of poisonous by-products adversely affect the conservation of natural eco-system.This paper focuses on estimation of energy consumption, energy savings, reduction of emissions of CO₂ for use of urban and rural household appliances in Mexico between 1996 and 2021.The analysis concentrates on six major energy end uses in the residential sector: refrigerators, air conditioners, washing machines, TV set, iron and heater.It is estimated that by 2021 there will be a cumulative saving of 22,605 GWh, as a result of the implementation of government programs on energy efficiency that represents a cumulative reduction of CO2 emissions of 15,087 Tg CO2.It means that Mexico can reduce in 5650 MW the generation capacity of national electricity system, which is to avoid burning 40.35 MM barrels of oil.The findings can be useful to policy makers as well as household appliances users.     

Energy and exergy analysis of prosumers in hybrid energy grids

Surplus energy can be a recurrent phenomenon in zero-energy buildings (ZEBs) with onsite generation systems, usually resulting in the export of excess electricity. Yet, converting electricity into heat and exporting it could improve the overall energy balance. This study analyses the energy and exergy performance of a Finnish nearly zero-energy building (nZEB) as a heat and electricity prosumer, and proposes alternative energy topologies to improve energy and exergy levels, primary energy demand and CO₂ emissions. The results show that increasing the installed capacity of the photovoltaic systems would lead to zero energy, exergy, emissions and a balance of primary energy. However, by instead using the surplus electricity to drive a heat pump and export heat, the currently installed capacity would lead to a net energy export of over 4000?kWh/a. Thus, energy conversion could significantly enhance the contribution from heat and electricity prosumers to smart energy grids, though not without affecting other criteria. Two management strategies arise: favouring heat export improves the net energy and CO₂ emissions reduction but lessens the net exergy, while favouring electricity export improves the net exergy and primary energy reduction. The findings highlight that energy conversion can enhance nZEB performance and its exchange with hybrid grids.     

Energy use, CO2 emissions and waste throughout the life cycle of a sample of hotels in the Balearic Islands

Tourism is the most developed economic sector in the Balearic Islands. The great rise in construction activities within the last 50 years, the increase in energy use, in CO₂ emissions and in waste production due to tourism, as well as an electrical energy production system mainly based on coal and fossil fuels is not an environmentally sustainable scenario. The aim of this study is to identify the processes that have had the greatest impact on the life cycle of a tourist building. In order to do this, the energy uses, CO₂ emissions and waste materials generated have been estimated, assuming a life cycle of 50 years, within a sample of hotels from the Balearic Islands. The results show that the operating phase, which represents between 70% and 80% of the total energy use, is the one with the greatest impact; that the energy use due to the manufacture of materials represents a fifth of the total and that electric consumption is the main cause of CO₂ emissions because of the regional energy system.     

Forecasting future cooling demand in London

Cooling of buildings in the UK is responsible for around 15 TWh per year of energy demand, largely powered by electricity with highly related CO₂ emissions. The Greater London Authority wished to understand the potential impact of London's growing need for cooling on UK CO₂ emissions in the period up to 2030. This paper describes a model developed to analyse the cooling requirements for London's key building stock and assess how these would be affected by change in system mix, improvements in system efficiencies, and by varying degrees of climate change.The analysis showed that, if left unchecked, the growth in active cooling systems in London could lead to a doubling of CO₂ emissions from this source by 2030. This growth will be due to increase in building stock, increase in market share of cooling systems, and climate change. The last of these is difficult to predict, but by itself could add 260,000-360,000 tonnes of CO₂ emissions by 2030. This increase can be strongly mitigated, or even offset, by improvements in system efficiency. The difference between no efficiency improvements, and an assumed 1-3% annual efficiency improvement is around 340,000 tonnes by 2030.     

Analysis of domestic hot water energy consumption in large buildings under standard conditions in Senegal

This paper presents an investigation of the energy consumption due to domestic hot water (DHW) production in large buildings. We have studied three types of reference buildings: one office, one residence and a 3-star hotel located in Senegal. The DOE2.1E (the building energy program of the Department of Energy Version 2.1E) has been used. One of its main advantage is that it allows to take into account both energy end use categories and a great number of parameters of the building energy performance. Four climatic regions have been identified and their equivalent “standard” conditions are all defined. Those conditions are the same as the current design and operating conditions of each type of building. The DHW energy consumption is calculated and compared with the total energy generated by all end uses (lighting, cooling/ventilation, DHW, and other equipment). Before we carry out wide and systematic simulations of the three buildings energy performance, we pay special attention to check and validate the DHW part of the DOE2.1E model. There was an agreement between the recorded monthly DHW energy load on the one hand, and on the other the computed results. We end up finding results that could open new perspectives for building a strategic methodology to provide guidelines for DHW energy saving measures in large buildings in West Africa. Furthermore, it is expected that energy researchers concerned about energy and environmental efficiency would consider this study for promoting CO₂ emission reduction in relation with DHW production in large buildings.     

Comparative study between a ceramic evaporative cooler (CEC) and an air-source heat pump applied to a dwelling in Spain

The study described in this paper aims to evaluate comparatively the interest of an implementation of a ceramic evaporative cooler (CEC) compared to the use of a conventional device such as an air-source heat pump. This comparison is presented in three closely related ways: energy consumption, environmental impact and economic costs. This analysis is based on the hypothetical cooling of a specific room in a dwelling in six Spanish cities, each characterised by a different climate. The behaviour of the CEC in each climate is determined experimentally, reproducing the typical air conditions by an air-treatment unit. The total cooling demand in each city during the summer months is obtained from the data of the thermal load evolution in the room, provided by thermal load calculation software.     

Development of a framework of key performance indicators to identify reductions in energy consumption in a medical devices production facility

The consumption of energy in manufacturing operations is growing in significance and approaches to reduce the resulting environmental impacts are necessary. Whilst companies have focused on reducing energy at a facilities level, research indicates that specific production processes generate significant environmental impact through energy consumption and greenhouse gas emissions. Potential energy savings have been identified in production processes; however the necessary tools are missing. The development of energy performance indicators have been described in theory but there is little evidence of their successful application in practice. This research proposes the application of a normalised co-efficient to view production and energy data and the development of a rolling energy performance co-efficient to provide alerts to ‘out-of-control’ production operations. Implementation of the approach in a large medical devices manufacturing facility has identified significant savings. Key consideration in the development of energy key performance indicators for production operations are described.     

Energy efficiency in Spanish wastewater treatment plants: a non-radial DEA approach

Wastewater treatment plants (WWTPs) are energy-intensive facilities. Thus, reducing their carbon footprint is particularly important, both economically and environmentally. Knowing the real operating energy efficiency of WWTPs is the starting point for any energy-saving initiative. In this article, we applied a non-radial Data Envelopment Analysis (DEA) methodology to calculate energy efficiency indices for sampling of WWTPs located in Spain. In a second stage analysis, we examined the operating variables contributing to differences in energy efficiency among plants. It is verified that energy efficiencies of the analyzed WWTPs were quite low, with only 10% of them being efficient. We found that plant size, quantity of organic matter removed, and type of bioreactor aeration were significant variables in explaining energy efficiency differences. In contrast, age of the plant was not a determining factor in energy consumption. Lastly, we quantified the potential savings, both in economic terms and in terms of CO₂ emissions, that could be expected from an improvement in energy efficiency of WWTPs.     

Using energy audits to investigate the impacts of common air-conditioning design and installation issues on peak power demand and energy consumption in Austin, Texas

This study presents an analysis of a unique dataset of 4971 energy audits performed on homes in Austin, Texas in 2009–2010. We quantify the prevalence of typical air-conditioner design and installation issues such as low efficiency, oversizing, duct leakage, and low measured capacity, and estimate the impacts that resolving these issues would have on peak power demand and cooling energy consumption. We estimate that air-conditioner use in single-family residences currently accounts for 17–18% of peak demand in Austin, and we found that improving equipment efficiency alone could save up to 205 MW, or 8%, of peak demand. We estimate that 31% of systems in this study were oversized, leading to up to 41 MW of excess peak demand. Replacing oversized systems with correctly sized higher efficiency units has the potential for further savings of up to 81 MW. We estimate that the mean system could achieve 18% and 20% in cooling energy savings by sealing duct leaks and servicing their air-conditioning units to achieve 100% of nominal capacity, respectively. Although this analysis is limited to the City of Austin, understanding the methods described herein could allow electric utilities in similar climates to make better-informed decisions when considering efficiency improvement programs.     

Energy efficient design and occupant well-being: Case studies in the UK and India

The purpose of this paper is to demonstrate the relationships between sustainable building design and occupant well-being. It starts with a definition of sustainable design and well-being, and focuses on the relationships between energy performance and occupant feedback. Methodologically it draws on detailed monitoring and surveys of 12 case study office buildings in the UK and India, and the paper uses the data to explore whether energy use and associated CO₂ emissions are correlated to occupant satisfaction and comfort. The results demonstrate that increased energy use in the case study buildings is associated with increased mechanisation (e.g. centralised air conditioning) and reduced occupant control. This reduced control in turn is shown to relate to reduced occupant comfort and satisfaction. Finally, the paper reveals that the reported health conditions of occupants correlates strongly with their levels of satisfaction. The overall conclusion is that energy use in typical office buildings is inversely correlated with the well-being of the occupants: more energy use does not improve well-being.