Comparing cost-optimal and net-zero energy targets in building retrofit

The recast of the European Union's Energy Performance of Buildings Directive introduced the concept of nearly zero-energy buildings, requiring its adoption from 2021 by all new buildings and existing ones submitted to major renovations. European Union member states must also ensure minimum energy requirements for buildings in order to achieve cost-optimal levels during their life cycle. Cost optimality and nearly zero-energy buildings are important concepts in European Union energy policies. These concepts are related, but one is more focused on costs, while the other is more concerned with low energy consumption and on site-renewable energy harvesting. If these approaches result in major differences in the selection of the best package of retrofit measures, then the transition from the cost-optimal concept to nearly zero-energy buildings might be problematic. To assess the most cost-effective solutions to achieve net-zero, a building in Porto, Portugal, was analysed. This determined not only the most cost-effective retrofit solutions but also compared these net-zero solutions with those resulting from the cost-optimal calculation. Both approaches lead to similar results, indicating that the transition between ‘cost optimality’ to ‘nearly zero-energy buildings’ could occur in Portugal.     

Elaboration of energy saving renovation measures for urban existing residential buildings in north China based on simulation and site investigations

It is necessary to determine whether to implement a retrofit measure or not based on its energy saving and economic benefits, when conducting a retrofit project. The common way to do that is to set up a building simulation model and calculate its energy saving and economic benefits. Because of the great discrepancy between the actuality and the building simulation model, it is very important to use the factual energy use to calibrate the model, so as to accurately predict the benefits of retrofit measures. Although the energy efficiency retrofit of residential buildings in north China is implemented in a large scale, it seldom knows whether the commonly used retrofit packages are optimized. Therefore, a typical residential building is selected in Beijing, and the energy saving and economic benefits of different retrofit measures are analyzed using a simulation model calibrated with its actual space heating energy use, and the optimized retrofit packages are put forward. Results shows the retrofit of space heating system is a very attractive measure due to its relatively low investment but good energy saving benefit, and roof retrofit is also cost effective, while window retrofit and wall retrofit are not economic to conduct separately. Four optimized retrofit packages are figured out to realize the 50% and 65% reductions of space heating intensity required in the energy efficiency standards, which have less investment costs compared with currently widely used packages, and the retrofit packages for the 65% reduction is more cost-effective than the packages for the 50% reduction.     

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.     

A multi-aid optimization scheme for large-scale investigation of cost-optimality and energy performance of buildings

According to the European Energy Performance of Buildings Directive (EPBD-2010/31/EU), all EU-Member states are obliged to continuously apply analysis on cost-optimal levels of minimum energy performance requirements towards nearly/net zero energy buildings. To perform such techno-economic analysis, a large number of technical/financial assumptions should be covered and possibly billions of design/operation options should be explored. This is computationally expensive. This study introduces a novel multi-aid optimization scheme (MAOS) for supporting robust cost-optimal decisions on energy-performance levels of buildings. The scheme's feature is reduction of the computational cost by avoiding time-consuming simulations through the use of post-processing and/or simplified models (when possible), while holistic optimization is adopted for considering multivariate interactions between possible design/operation options and financial/technical assumptions. The effectiveness of MAOS is demonstrated by optimizing a single-family house under 108-financial scenarios, where more than 1.6¹⁰ solutions would be possible. The results show significant (～95%) time reduction compared with those of the usual simulation-based optimization approach.     

建筑运行能耗监测与节能诊断系统的开发

国家机关办公建筑和大型公共建筑的高耗能问题日益突出,该类建筑的节能改革正成为当前建筑节能工作的重点,因此做好此类建筑运行能耗尤其是暖通空调设备运行能耗的监测与节能诊断分析对实现"十一五"节能目标有重要意义.本文设计开发了建筑运行能耗监测与节能诊断系统硬件子系统,该系统不仅能监测耗能量,还能监测用能品质.主要研究内容包括以MS SQL Server 2000作为平台设计了能耗监测与数据信息数据库系统,开发了建筑运行能耗监测数据采集服务器程序与客户端查询分析程序,建筑用户凭密码可在网上查询最新的监测数据并得到分析报告,从而帮助建筑用户实现能源系统由粗放型管理转变为精细型、科学化管理.在此系统基础上,通过工程案例分析,发现空调系统中存在严重的"大流量、小温差"现象和电力系统中存在"三相不平衡"能源浪费问题.     

寒冷地区高校既有建筑节能技术体系研究

当前,降低建筑能耗的投资约为降低工业能耗投资的5倍,因此建筑节能的能效水平及技术的经济性就尤为重要。基于我国为数众多的各类高校已成为国内重要的能源消耗大户,以寒冷地区高校既有建筑为研究对象,阐述通过能耗调查和测试数据,进行建筑能耗模拟分析,可找到既有建筑能耗的关键问题,并确立节能改造原则,制定相应的节能技术体系,此为解决高校既有建筑节能问题的关键。对技术的应用则应针对不同的既有建筑能耗特点和改造资金投入状况,进行灵活的技术组合和应用,构成不同层次的节能技术群,使得改造得以真正地实施。     

Building energy use compilation and analysis (BECA). Part C: Conservation progress in retrofitted commercial buildings

Data on actual energy use were compiled for 223 retrofitted U.S. commercial buildings and analyzed for several quantities of interest: average savings, average retrofit cost, correlation between cost and savings, type of retrofit attempted, etc. Dominant building types were schools and offices; nearly all buildings included operations and maintenance changes as part of the retrofit. Eight-nine per cent. of the buildings which saved energy by retrofitting achieved a payback (simple) in less than 3 years. Nine per cent. of the buildings failed to save (generally because of improper maintenance), indicating there is some risk in conservation investment. Average savings for the entire sample were 20 per cent., at an average cost of $0.62 per square foot. On a more limited subsample, energy savings predictions made by the auditors prior to retrofit were compared with actual energy savings. About 60 per cent. of the time, actual savings exceeded predictions. Data were available on 15 buildings for savings achieved over a number of years following the retrofit; in most cases the savings persisted, and even increased.     

既有建筑钢窗节能改造性能分析

建筑外窗是影响建筑热环境和造成建筑能耗过高的主要原因,对其实施节能改造是降低既有建筑能耗的有效措施之一。目前针对金属钢窗的节能改造主要是采取整体更换方式进行,不但费时、扰民,而且破坏性强、材料浪费严重。针对这个问题,提出了一种新型的节能改造方法——"塑钢复合法",研究结果显示,该方法不但具有较好的节能效果,而且成本较低。     

A cost effective approach to design of energy efficient residential buildings

The objective of this study is to identify cost-optimal efficiency packages at several levels of building energy savings. A two-story residential building located in Jordan is selected as a case study. DesignBuilder software is used to predict the annual energy usage of a two-story residence in Irbid, Jordan. Real-time experimental data from a single isolated controlled room was used to verify the proposed model. In addition to energy analysis, the economic, environmental, and social benefits of the proposed design have been investigated. The sequential search optimization approach is used to estimate the minimum cost of the building while considering various design scenarios. In addition, the impact of various energy conservation techniques on residential buildings is assessed, and the payback period for each program is calculated. Ultimately, the optimal combination of design to achieve energy efficiency measures has been identified in several climate regions. The simulations results predict that the annual electricity consumption can be reduced up to 50% if the proper combinations of energy conservation measures are selected at the lowest cost. The payback period is 9.3 years. Finally, energy efficiency measures can lead to a total of 9470 jobs/year job opportunities.The study provide practical framework to link between energy performance criteria and economic goals of building. Linking the energy performance requirements to economic targets provides guidelines for homeowners, contractors, and policymakers for making a suitable decision regarding the retrofitting of existing residential buildings. The study focuses on developing new methodologies that support minimizing costs during a building's lifecycle while maximizing environmental benefits which can not be identified by a series of parametric analyses using individual energy-efficient measures.     

夏热冬冷地区居住建筑节能65%的探讨——以杭州市"景上公寓"建筑节能示范项目为例

实施节能65%是夏热冬冷地区居住建筑下一步节能工作的重点.结合杭州"景上公寓"节能示范工程,探讨了该地区居住建筑实施节能65%标准的可行性.通过CHEC节能计算软件对示范工程进行节能计算,从而对节能率、围护结构节能要求和标准进行了分析;同时,根据夏热冬冷地区的气候特点,结合示范工程的实际情况,进一步对杭州地区居住建筑节能设计的相关问题进行了探讨.     

Very low energy homes in the United States: Perspectives on performance from measured data

We present measured annual performance data from a dozen recent-vintage very low energy homes in North America. Many of the designs combine greater energy efficiency with solar electric photovoltaic power in an attempt to create Zero Energy Homes (ZEH). We also provide measured data from the first home constructed to the German Passivhaus standard in the United States. Several projects either exceeded or come very close to true net zero energy when evaluated over a year.The data indicate that very low energy use buildings can very readily be achieved in North America. Annual energy use half that or less than standard housing can be achieved for an equivalent cost of $0.10/kWh from the efficiency investment. In general, the better cost effectiveness seen from energy efficiency measures indicates that greater investment in conservation should be a prerequisite to installation of solar water heating and solar electricity in Zero Energy Homes. However, over emphasis in efficiency is also possible. This suggests that optimization tools such as BEopt and EGUSA, which characterize both renewable resource performance and that also of specific combinations of energy efficiency measures, will best guide designers to locate the most economically favorable mix to reach an energy neutral level.     

The effects of an energy efficiency retrofit on indoor air quality

To investigate the impacts of an energy efficiency retrofit, indoor air quality and resident health were evaluated at a low‐income senior housing apartment complex in Phoenix, Arizona, before and after a green energy building renovation. Indoor and outdoor air quality sampling was carried out simultaneously with a questionnaire to characterize personal habits and general health of residents. Measured indoor formaldehyde levels before the building retrofit routinely exceeded reference exposure limits, but in the long‐term follow‐up sampling, indoor formaldehyde decreased for the entire study population by a statistically significant margin. Indoor PM levels were dominated by fine particles and showed a statistically significant decrease in the long‐term follow‐up sampling within certain resident subpopulations (i.e. residents who report smoking and residents who had lived longer at the apartment complex).     

A screening methodology for implementing cost effective energy retrofit measures in Canadian office buildings

Private and public sectors own and operate an array of office buildings that consume energy and contribute to the emission of greenhouse gases (GHG). Energy demands can be reduced by applying energy retrofit measures (ERMs) to existing buildings. The choice of ERMs involves evaluation of applicability, energy end uses and cost of application versus energy savings. This paper describes a methodology developed to screen office buildings for their current level of energy consumption and potential for retrofit application. Selection of an optimal set of ERMs is influenced by climate, occupancy, heating and cooling systems, envelope properties and building geometry. When assessing the implications of applying ERMs to a large building stock it is vital to screen the complete building set for optimal retrofit opportunities. This can be accomplished by characterizing office building stock into a manageable set of archetypes and simulating building operation using energy simulation software. Using regression analyses, a model was developed for estimating the energy consumption. Present value analysis was used to optimize the evaluation of the various ERMs. The methodology developed can be used to simplify the ranking of buildings for retrofit; to select and combine ERMs, and to plan energy and GHG reduction activities.     

北方供暖地区既有居住建筑节能改造技术支撑

从当前国家建筑节能形势出发,简单阐述了北方供暖地区既有居住建筑节能改造的必要性。分析比较了近年来国内外既有居住建筑改造实例,探讨了我国北方既有居住建筑节能改造的若干技术问题。分析了节能改造各环节技术路线的基本要求,介绍了节能改造的评估与诊断方法,具体分析了节能改造的技术方案。     

Unequal spatial distribution of retrofits in Bucharest’s apartment buildings

This paper argues that the current spatial patterns of energy retrofits in post-socialist apartment buildings are unequally distributed across municipalities in Bucharest, Romania. In addition to the dominant techno-economic and social framing of this type of retrofit action, an institutional and political perspective can provide useful insights into why this occurs. By drawing on secondary analysis of statistical data, grey literature and 20 semi-structured interviews in Bucharest, three important findings emerge. First, the institutional complexity of energy retrofit of apartment buildings in Romania is underestimated and the interaction between various institutions is poor, explained by lack of trust and collective action. Second, the spatial distribution of the retrofit of apartment buildings is unequally distributed across Bucharest’s six municipalities. Third, current action for retrofit does not reach municipalities with the greatest need and potential. A more bottom-up and decentralized institutional landscape exists than is currently acknowledged in public policy and the research literature. Findings show an unequal and unfair spread of retrofit action within and between cities – raising wider implications for the potential shortcomings of European Union retrofit programmes in Central and Eastern Europe.     

Enhancing the sustainability and energy conservation in heritage buildings: The case of Nottingham Playhouse

Today, there is a growing interest in developing energy efficient buildings since it is estimated that buildings account for about 40% of the total primary energy consumption in the world. In relation to existing buildings, energy efficiency retrofits have become an important opportunity to upgrade the energy performance of commercial, public and residential buildings that may reduce the energy consumption, demand and cost. In this paper we cover the energy efficiency deep retrofit process that has been carried out for Nottingham Playhouse theatre building for the aim of enhancing its environmental performance and analysing the energy efficiency gained after implementing certain proposed modifications. It is a nationally protected historic building, listed as Grade II1 on The National Heritage List for England (NHLE). The building has had insulation enhancement, doors modifications, solar energy installations, energy-saving lights, in addition to improved heating and air conditioning system. The paper presents a novel methodology; and its results indicate significant improvements in the building's energy performance which is demonstrated using infrared thermographic images and data logger sensors where significant energy savings to the building's thermal performance are obtained. The energy saving measures have been completed while maintaining the heritage building's general appearance and architectural features, which have received a Commendation Certificate from The Nottingham Civic Society for this achievement.     

Measurements of occupancy levels in multi-family dwellings—Application to demand controlled ventilation

The occupancy level of dwellings is an important parameter to know to determine the energy efficiency, energy use and indoor air quality, especially in low-energy buildings where the user-related energy uses, such as household electricity and domestic hot water heating, are significant parts of the energy balance in a building. For residential buildings, there is a lack of occupancy level data, which also needs to be resolved over time, in a way so that both short term and long term variations can be described. As a part of an ongoing study, occupancy levels were measured as building average levels in 18 apartment buildings containing 342 apartments in total with readings every 30 min for more than a year. Averages and standard deviations of occupancy level, and variation in occupancy during the year, week and day respectively are presented. The results show a highly varying occupancy level over time, which indicates the potential of demand controlled ventilation in dwellings.     

Unequal access to energy efficiency in US multifamily rental housing: opportunities to improve

The energy efficiency of US multifamily rental housing is compared with other housing types. A real and growing energy efficiency gap is documented, particularly for lower income households. Findings are based on data from the 2005 and 2009 US Residential Energy Consumption Survey (RECS). Individual energy efficiency features related to HVAC (heating, ventilation and cooling) systems, appliances, and the building envelope are analysed along with weighted and unweighted total energy efficiency indices. Multifamily units occupied by low income renters had 4.1 fewer energy efficiency features in 2005 and 4.7 fewer in 2009 compared with other households. If the number of efficiency features was on par with other housing, the savings could be in the range of US$200–400 per year for most lower-income renters in multifamily buildings. There is an astonishing lack of information on how efficiency retrofits would affect property (real estate) metrics such as cash flow and value. Available evidence suggests that millions of US properties could be good retrofit investment opportunities. Better efficiency would allow renters to increase spending on food, healthcare and other essentials. This is not only an economic issue: it has implications for household health, social equity and environmental problems tied to energy consumption.     

既有办公建筑节能改造技术经济效果分析研究

既有建筑节能改造是建筑节能工作的重要任务.以山东省某办公大楼节能改造试点经验为基础,对谊建筑改造后的节能率、节能投资、节能收益及投资回收期进行了分析研究,其结果可供既有建筑节能改造借鉴.     

基于市场特征的既有建筑节能改造中业主的行为分析

既有建筑节能改造是建筑节能的重要组成部分,主体行为是既有建筑节能改造成功的关键.本文在对既有建筑节能改造市场正外部性、信息不对称性以及动力乏失等特征进行分析的基础上,构建了业主间博弈模型,可知通过采取激励约束政策可以转移信息不对称性下业主的最优策略.而后,通过分析业主在市场信息获取中的“单向行车道”问题,提出了解决信息不对称性下业主逆向选择的对策.最后,运用经济学理论分析了业主在市场供给—需求下动力乏失的原因,并给出了相应对策.