The impact of energy efficient refurbishment on the space heating fuel consumption in English dwellings

The aim of this study is to examine the effect of a major domestic energy efficiency refurbishment programme on domestic space heating fuel consumption. The case study dwellings were monitored either before or after (or both) the introduction of energy efficiency retrofit measures such as cavity wall insulation, loft insulation, draught stripping and energy efficient heating system. Property and utility consumption data were collected and half-hourly living room and main bedroom temperatures were monitored for 2–4 week period over two winters from a total of 1372 households selected from five major urban areas in England. Space heating fuel consumption was normalized to account for variation in the indoor–outdoor temperature difference and the dwelling floor area. The findings show that cavity wall and loft insulation can reduce the space heating fuel consumption by 10% in centrally heated properties and 17% in non-centrally heated properties. However, the introduction of a gas central heating system, although theoretically more efficient, has no significant impact in reducing fuel consumption even after adjusting for increased internal temperature.     

Occupant related household energy consumption in Canada: Estimation using a bottom-up neural-network technique

A national model of residential energy consumption requires consideration of the following end-uses: space heating, space cooling, appliances and lighting (AL), and domestic hot water (DHW). The space heating and space cooling end-use energy consumption is strongly affected by the climatic conditions and the house thermal envelope. In contrast, both AL and DHW energy consumption are primarily a function of occupant behaviour, appliance ownership, demographic conditions, and occupancy rate. Because of these characteristics, a bottom-up statistical model is a candidate for estimating AL and DHW energy consumption. This article presents the detailed methodology and results of the application of a previously developed set of neural network models, as the statistical method of the Canadian Hybrid Residential End-Use Energy and Greenhouse Gas Emissions Model (CHREM). The CHREM estimates the national AL and DHW secondary energy consumption of Canadian single-detached and double/row houses to be 248 PJ and 201 PJ, respectively. The energy consumption values translate to per household values of 27.8 GJ and 22.5 GJ, and per capita values of 9.0 GJ and 7.3 GJ, respectively.     

Uptake of energy efficiency interventions in English dwellings

Little detailed evidence has previously been available regarding the uptake rate or prevalence of energy efficiency interventions among specific household groups. This study uses the Home Energy Efficiency Database (HEED) to investigate both the combination of measures that have been installed, and in which dwellings, according to key neighbourhood socio-demographic variables, including income and tenure. Analysis of 2000–07 data indicates that approximately 40% (9.3 million) dwellings in England had approximately 23.7 million efficiency measures installed, with an average of 2.5 measures per dwelling. Building fabric-related measures were the most frequent (e.g. cavity wall insulation, loft insulation and glazing) with an average of 2.1 million installed each year. Dwellings with the highest number of fabric interventions (the top 20%) were more likely to be found in areas with low income, with more owner-occupied dwellings, experiencing lower winter temperatures, having a lower proportion of flats, and having a slightly higher proportion of older adults and children. Energy efficiency installations have tended to occur among specific types of households or parts of the building stock. These findings have implications for the design of future government programmes for targeting energy efficiency measures to specific household groups or dwelling types.     

Field assessment of thermal behaviour of historical dwellings in France

In many countries, there is a great number of old buildings with local architectural, patrimonial, aesthetic and historic interest. They are the products of the vernacular traditional architecture fully integrating the environmental, social and economic local constraints.Moreover, this built inheritance is more heterogeneous than the modern stock of existing buildings. The historical buildings were built with different architectural designs featuring local styles of construction, different techniques and historical expertise.By experience, the actors of the building sector know that the thermal behaviour of historical buildings are not those of modern buildings set up at the time of the industrial period. However, they do not have assessed these specific thermal characteristics of historical buildings.This paper describes the complexity of architectural designs of historical dwellings in France. A field investigation during one year highlights various thermal characteristics of 11 dwellings. It provides a new understanding of thermal behaviour of these historical dwellings. The results show the thermal characteristics of historical dwellings and their differences with modern architecture.     

Environmental impact of building-related and user-related energy consumption in dwellings

Energy consumption in dwellings contributes significantly to their total negative environmental impact. This paper quantitatively assesses the environmental impact of building-related and user-related gas and electricity consumption in a Dutch apartment dwelling using life cycle assessment (LCA) methodology. Several scenarios for gas and electricity consumption are compared to assess what effect changes in building characteristics and user behaviour have on the environmental impacts of energy consumption. This study shows that gas consumption significantly contributes to four environmental impact categories, which can be most effectively countered by reducing the heat demand of the dwelling. A 23% reduction in gas consumption leads to up to 13% less overall environmental impacts. Particularly in buildings with low heat demand, electricity consumption dominates all environmental impact categories. These can most effectively be reduced by changing the electricity demand of the user: 47% less electricity consumption leads to a 9–45% reduction in the total environmental impact. However, since electricity consumption continues to rise, the environmental effects of electricity use may be better reduced by changing the environmental impact of the electricity supply. Theoretically, when electricity consumption remains the same, over 90% less environmental impact could be reached by using 100% wind power to generate electricity.     

Indoor air quality in energy‐efficient dwellings: Levels and sources of pollutants

Worldwide, public policies are promoting energy‐efficient buildings and accelerating the thermal renovation of existing buildings. The effects of these changes on the indoor air quality (IAQ) in these buildings remain insufficiently understood. In this context, a field study was conducted in 72 energy‐efficient dwellings to describe the pollutants known to be associated with health concerns. Measured parameters included the concentrations of 19 volatile organic compounds and aldehydes, nitrogen dioxide, particulate matter (PM_2.5), radon, temperature, and relative humidity. The air stuffiness index and night‐time air exchange rate were calculated from the monitored carbon dioxide (CO₂) concentrations. Indoor and outdoor measurements were performed at each dwelling during 1 week in each of the two following seasons: heating and non‐heating. Moreover, questionnaires were completed by the occupants to characterize the building, equipment, household, and occupants’ habits. Perspective on our results was provided by previous measurements made in low‐energy European dwellings. Statistical comparisons with the French housing stock and a pilot study showed higher concentrations of terpenes, that is, alpha‐pinene and limonene, and hexaldehyde in our study than in previous studies. Alpha‐pinene and hexaldehyde are emitted by wood or wood‐based products used for the construction, insulation, decoration, and furnishings of the dwellings, whereas limonene is more associated with discontinuous sources related to human activities.     

Survey of occupant behaviour and control of indoor environment in Danish dwellings

Repeated surveys of occupant control of the indoor environment were carried out in Danish dwellings from September to October 2006 and again from February to March 2007. The summer survey comprised 933 respondents and the winter survey 636 respondents. The surveys were carried out by sending out invitations to addresses obtained from a Danish register along with information on dwelling characteristics. Meteorological data was obtained from the Danish Meteorological Institute.Four control mechanisms (window open/closed, heating on/off, lighting on/off and solar shading in/not in use) were analysed separately by means of multiple logistic regression in order to quantify factors influencing occupants’ behaviour.The window opening behaviour was strongly related to the outdoor temperature. The perception of the environment and factors concerning the dwelling also impacted the window opening behaviour.The proportion of dwellings with the heating turned on was strongly related to the outdoor temperature and the presence of a wood burning stove. The solar radiation, dwelling ownership conditions and the perception of the indoor environment also affected the use of heating.The results of the statistical analyses form a basis for a definition of standard behaviour patterns which can be used to make calculation of energy consumption of buildings more accurate.     

Comparison between measured and calculated energy performance for dwellings in a summer dominant environment

The objective of this study is to present a comparison between the measured and the calculated energy performance of dwellings. For this purpose, the energy consumption of ten dwellings is measured for one year. The added value of this work is that it is performed in a summer dominant environment. The energy needs of the same dwellings are also calculated by means of the methodology based on European Standards described in the CEN/TR 15615:2008 technical report. According to the findings of this study, a large gap exists between the calculated and the measured energy consumption of the examined dwellings. In order to evaluate the reasons for this deviation, a detailed analysis of the heating and cooling loads of the dwellings is performed. The intermittent heating of the building is found to be simulated accurately by the employed methodology, whereas the comparison between the calculated and the measured cooling loads reveals a large deviation of about 150%. Based on the findings of this study, a factor of 0.6 should be adopted in the case of cooling schedule, compared to the heating operation of the building.     

Rice milling industry in India: energy saving potential of energy efficient motors

A somewhat generalised framework for estimating the energy savings potential of energy efficient motors in the rice milling industry in India has been proposed. Relationship between the paddy processing capacity of the rice mill and its power rating has been developed from the available data. For realistic estimation of power rating, new factors have been proposed. Regression curves of motor efficiency on its power rating have also been developed for both standard and energy efficient motors. Based on these relationships, the energy savings potential for various cases has been estimated. Finally, the financial feasibility of using energy efficient motors in place of standard motors in rice milling industries has been evaluated.     

The impact of energy externalities on the cost effectiveness of energy efficiency measures applied to dwellings

European Union and UK energy policy recognise the potential contribution the domestic housing sector can make in reducing energy consumption. In the UK, improvements to existing dwellings are likely to play a critical role in realising such potential. The need to consider both the value and uncertainty of external environmental and social costs in developing effective policy is also made explicit.This analysis investigates the impact of such values and uncertainties on the relative performance of a range of insulation measures applied retrospectively to an existing residential dwelling.Results from a case study suggest that large variations in capital cost, energy saving potential and the value of externalities have a significant impact on the relative cost effectiveness of these measures. However, in general, current investment decision-making based on normal market energy prices and today's climate is likely to deliver solutions that remain effective under significant levels of uncertainty.     

Integrating the rebound effect: accurate predictors for upgrading domestic heating

One particular definition of the ‘rebound effect’ has won acceptance for its conceptual clarity and mathematical robustness: the energy efficiency elasticity of demand for energy services. This is formulated as a partial differential, and its structure enables transformations with price and energy elasticities. However, when considering heating energy efficiency upgrades of homes, the mathematical predictions can be unreliable because these upgrades involve large changes in efficiency, energy and energy services, whereas differential calculus only holds true for very small changes. This could be one reason why existing estimates of rebound effects are so diverse. This paper shows how this limitation can be remedied, using the German housing stock as a case study. A curve of consumption/efficiency for this stock is derived from empirical studies and, based on the mathematical definition of the rebound effect, a rebound effect relation is derived from this. This curve is then integrated over the likely ranges of energy efficiency upgrades that would correspond to the government's policy of reducing consumption by 80%. The model is found to be mathematically coherent, and suggests energy service rebounds of 28–39% for the German stock as a whole if the 80% goal is achieved.     

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

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

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

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

Measuring the rebound effect: A case study of residential photovoltaic systems in San Diego

This study examines the effect of solar photovoltaic system installation on the electricity consumption in residential households across various geographic regions in San Diego. Using meter-level data, the electricity consumption for residential households is calculated before and after installation to assess whether there are any significant rebound effects in usage. Results reveal significant variations in the change in electricity usage depending on geographical location. The findings are relevant to regional resource planning and climate response, as the failure to account for the rebound effect may result in significant overestimation of the energy and emissions benefits of distributed renewable energy adoption.     

Network effect of transportation infrastructure: a dynamic panel evidence

This study examines the effects of transportation infrastructure (motorways) on economic growth by using a dynamic model for panel data of 19 OECD countries. The results indicate a significant nonlinear network effect of motorway extensions. Specifically, motorway construction has an increasingly positive effect as the network expands.     

Criteria for energy efficient lighting in buildings

In order to assess the energy efficiency of an indoor lighting installation, a criterion for the installed electrical power is proposed which is broadly applicable and easy to use. Introducing target values for lamps and gear and taking into account some basic lighting comfort requirements, the maximum electrical power to be installed can be predicted for any kind of application. Herewith, one or more task areas with appropriate target illuminance values may be defined. The key parameter of the criterion is the analytical expression for the target utilance as a function of common lighting design parameters.Two practical examples illustrate the validity of the criterion. In a first example, a general case where the task area is coincident with a reference plane parallel with the floor has been studied. The values obtained converge to actual target values in current practice. In a second example, the lighting design of a store with many vertical task areas is explained. These cases illustrate the advantages of the criterion as compared to energy evaluation criteria based on the normalized power density.From 2010 on, the proposed criterion will be used in Flanders to assign grants for a re- or newlighting.     

节能结构体系综述

建筑节能作为现代技术的一个发展方向,已成为国内外建筑业广泛重视的研究课题。介绍几种广泛应用的节能结构体系及其构造特点。指出发展节能结构体系是缓解我国能源紧缺矛盾、改善人民生活环境质量、减轻环境污染、实现可持续发展战略目标的关键。     

The anatomy of investing in energy efficient buildings

A building investment is a real decision because the allocated resources are typically irrevocable for long times. Investment appraisal is a logic method to process elapsing time, uncertain benefits and costs, and irrevocability related to decisions. Most analysts stop halfway the appraisal process when they carefully assess net present values and their sensitivity to uncertain future events. But sidelining irrevocability and the dynamic sequential analysis of future events and actions cause wrong decisions when the energy performance endowment of a new building is decided. Irrevocability and preclusion are explained, and their impact illustrated with a case study. Adopting realistic assumptions about the uncertain future and applying the proper methodology reveal as financially best choice the immediate investment in passive attributes and items. Irrevocability is of high relevance for building efficiency investments and for the implementation of the EU-2010 buildings directive.