Measured energy savings from residential retrofits: Updated results from the BECA-B project

This study summarizes measured data on energy savings from conservation retrofits in existing residential buildings. We have compiled building performance data on approximately 115 retrofit projects (almost twice the size of the initial study) that we put into four general categories: utility-sponsored conservation programs, low-income weatherization programs, research studies, and multifamily buildings. The sample size for each project varies widely, ranging from individual buildings to 33 000 homes. Retrofits to the building shell, principally insulation of exterior surfaces, window treatments, and infiltration-reduction measures, are the most popular, although data on various heating system retrofits are now available. The average retrofit investment per unit in multifamily buildings is approximately $695, far lower than the average of $1350 spent in single-family residences. The median annual space heat savings in the four categories range from 15 to 38 GJ. Savings achieved are typically 20%–30% of pre-retrofit space heating energy use although large variations are observed both in energy savings and in costs per unit of energy saved. Even given the wide range in savings, most retrofit projects are cost-effective. Approximately 75%–80% of the retrofit projects have costs of conserved energy below their respective space heating fuel or electricity prices.     

Retrofit cost-effectiveness: Estonian apartment buildings

The economic viability and investment cost of the energy retrofit of apartment buildings are analysed through different energy efficiency levels. To analyse retrofit policy cost-optimal energy efficiency levels and investment costs, a baseline of measured actual energy usage of apartment buildings was created and then individual energy-saving measures and retrofit packages were composed. The cost-optimal level over a 20-year period for apartment building retrofit was a low-energy-building energy performance level, with an investment cost of €150–170/m². Retrofit to low energy building level would be economically viable but the investment capability of apartment owner associations is found to be insufficient for the necessary investments to achieve low-energy-building energy performance. Therefore, it is necessary to determine what levels of financial support can encourage retrofit to occur. The analysis of the current retrofit shows that subsides will increase investment by apartment owner associations into energy efficiency improvements. The target group for energy efficiency retrofit subsidies should be apartment buildings that reach low energy building performance level or at least match the energy performance requirement for new buildings.     

Actual electricity savings and audit predictions for residential retrofit in the pacific northwest

An important and unresolved issue concerning home energy audit programs is the accuracy of the engineering calculations. That is, the accuracy of audit predictions of energy savings for recommended retrofit measures is generally unknown. Data available from a recent evaluation of the Bonneville Power Administration Residential Weatherization Pilot Program allow comparison and analysis of the relationships between actual electricity savings and audit estimates of likely savings.The BPA program offered free home energy audits to identify cost-effective conservation measures to reduce space and water heating electricity use. The program also offered zero-interest, deferred-payment loans for installation of measures recommended during the audit.The actual reduction in annual electricity use averaged 4130 kWh across participant households. The cost of the retrofits that yielded this saving averaged $2100. The median ratio of actual-to-estimated saving is 0.66. Thus, on average, two thirds of the expected saving is actually realized. However, there is substantial variation in this ratio. Actual electricity use increases in the second year for more than 10% of these homes. On the other hand, actual savings are more than double the audit estimates in more than 10% of the homes.     

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.     

A case study for the evaluation of realistic energy retrofit strategies for public office buildings in the Southern Hemisphere

The building sector offers significant opportunities for reducing the energy consumption with considerable economic, environmental and health benefits. Governments can lead the way by retrofitting existing public buildings to reinforce their commitment to improve energy efficiency. Similar design standards, end-uses and operational profiles are usually established for public buildings based on the services they offer. Retrofitting a public building can therefore serve as an ideal test-bed for energy efficiency measures for other buildings within a particular service category. This study first analysed the current electricity consumption of a public office building in Mauritius, located in the Southern Hemisphere. A complete model of the building was created, validated and then simulated to investigate the impact of realistic retrofit strategies on the electricity consumption. Results showed that lighting retrofit achieved the most significant reduction while measures that improved the thermal envelope of the building resulted in smaller energy savings. The possibility of exploiting solar energy was explored by simulating a 70 kW_p photovoltaic system installed on the roof. An equivalent of 8.5% of the annual electricity consumption of the building could thus be generated. A financial analysis is also presented for all retrofit scenarios in terms of annual return and payback period.     

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

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

The use of tuff stone cladding in buildings for energy conservation

Heating the houses in cold climates requires large quantities of heat energy to be spent. The building sector consumes more energy in the form of heat than other sectors. Therefore, considerable energy savings can be obtained by using natural rocks with low thermal conductivity in insulating the buildings. In this study, the amount of energy conserved by using porous tuff stone in external walls of buildings is calculated. It was shown that considerable energy savings can be achieved by using tuff stone for facing buildings in cold climate zones such as Isparta region. The cost of installing tuff stone panels for facing buildings will be paid back in four years by savings in heat energy.     

Building energy use compilation and analysis (BECA). Part B: Retrofit of existing North American residential buildings

BECA-B assesses the technical performance and economics of energy conservation retrofit measures. The data collected thus far represent measured energy savings and retrofit costs for over 65 North American residential retrofit projects. The samples size within each project ranges from individual homes to 33 000 dwellings participating in a utility-sponsored program. The median value of space heating energy savings is 24% of the pre-retrofit consumption. For fuel-heated homes, the median cost of conserved energy is $3.66/GJ, substantially less than the U.S. Average 1981 prices for purchased energy of $4.27/GJ for natural gas and $8.25/GJ for fuel oil. For ten of the eleven electric heat retrofits the cost of conserved electricity is less than the 1981 U.S. average price of 6.2¢/kWh.     

Analysis of an information monitoring and diagnostic system to improve building operations

This paper discusses a demonstration of a technology to address the problem that buildings do not perform as well as anticipated during design. We partnered with an innovative building operator to evaluate a prototype information monitoring and diagnostic system (IMDS). The IMDS consists of a set of high-quality sensors, data acquisition software and hardware, and data visualization software including a web-based remote access system, that can be used to identify control problems and equipment faults. The information system allowed the operators to make more effective use of the building control system and freeing up time to take care of other tenant needs. They report observing significant improvements in building comfort, potentially improving tenant health and productivity. The reduction in the labor costs to operate the building is about US$ 20,000 per year, which alone could pay for the information system in about 5 years. A control system retrofit based on findings from the information system is expected to reduce energy use by 20% over the next year, worth over US$ 30,000 per year in energy cost savings. The operators are recommending that similar technology be adopted in other buildings.     

Energy budgets for office buildings?

To study the feasibility of devising energy performance codes – energy budgets – for office buildings, a major Canadian research project monitored the performance of existing buildings to verify a computer programme, which then provided a model for testing the effect on energy consumption of independent variables. The results showed that building height is far more important than size, and that shape and climatic location can be allowed for in relatively simple formulae. The knowledge thus gained, when applied to calculate the effect of better energysaving measures for the office blocks chosen, indicated potential savings of 44–50 per cent with little capital cost.     

The life cycle impact of refurbishment packages on residential buildings with different initial thermal conditions

Existing buildings constitute a large portion of the UK’s housing stock. Refurbishment of existing buildings can, therefore, have an important role in achieving the UK government’s CO₂ reduction targets. While building regulations and rating frameworks mainly focus on the improvements of the operational performance of buildings, Life Cycle Analysis is considered to be a more appropriate framework to account for long–term CO₂ savings. This study evaluates a range of retrofit approaches (simple, medium, and deep), in terms of Life Cycle Carbon Footprint applied on a terraced house—one of the most common housing archetypes in London. The initial state of the original building has also been examined assuming three initial states (never refurbished, refurbished in compliance with the 1976 and with the 2000 building regulations). Results showed that for all initial state scenarios, deep retrofit achieved the lowest life cycle carbon emissions, in absolute figures, compared to the simple and medium retrofits. Simple retrofit packages, on the other hand, achieved quick and significant improvements, especially in buildings with poor initial thermal conditions. The study also indicated that retrofit packages applied on highly efficient building fabrics result in longer carbon payback time periods. The study recommends establishing a ‘staggered’ retrofitting approach, which pushes for ‘older building first’ and ‘simple retrofit packages first’, as these gain quick CO₂ savings. Deep retrofit packages and treatment of relatively new buildings should be implemented at a later stage, to push buildings further to Zero–Carbon target.

     

大型商场节能改造案例研究

大型商场具有内区大、内热扰大、能耗密度大、基本常年需供冷等特点,是大型公共建筑节能改造的重点之一。本文以一个实际的大型商场节能改造为典型案例,通过介绍其节能改造过程及技术,为大型公共建筑或类似建筑的节能改造提供借鉴参考。该案例改造前后能耗实测对比,建筑年能耗约降低98万度电,单位建筑面积中央空调系统能耗由121kWh/m2降低到75kWh/m2,中央空调系统节能率达到38%。     

Comparison of actual energy savings with audit predictions for homes in the north central region of the U.S.A.

Utilities throughout the U.S. offer their customers on-site home energy audits. The main purpose of these audits is to give households specific suggestions on cost-effective conservation measures suitable for their home. Unfortunately, little is known about the accuracy of these audit procedures or on the actual energy savings achieved in these homes. Data from a recent evaluation of a home energy audit program in Minnesota were used to analyze the actual energy savings achieved in audited homes and the relationship between actual and predicted savings. The actual reduction in weather-adjusted natural gas use for 346 gas-heated single-family homes averaged 19 M Btu/year. The variation, however, was quite large: gas use increased in almost 20% of the homes, while gas use decreased by more than 50 M Btu/year in 10% of the homes. The median ratio of actual-to-predicted gas saving was 0.66, suggesting that, on average, two-thirds of the expected energy saving was actually realized. However, the actual saving was within 50% of the audit prediction in only 45% of the homes studied.     

Do LEED-certified buildings save energy? Yes, but…

We conducted a re-analysis of data supplied by the New Buildings Institute and the US Green Buildings Council on measured energy use data from 100 LEED-certified commercial and institutional buildings. These data were compared to the energy use of the general US commercial building stock. We also examined energy use by LEED certification level, and by energy-related credits achieved in the certification process. On average, LEED buildings used 18-39% less energy per floor area than their conventional counterparts. However, 28-35% of LEED buildings used more energy than their conventional counterparts. Further, the measured energy performance of LEED buildings had little correlation with certification level of the building, or the number of energy credits achieved by the building at design time. Therefore, at a societal level, green buildings can contribute substantial energy savings, but further work needs to be done to define green building rating schemes to ensure more consistent success at the individual building level. Note, these findings should be considered as preliminary, and the analyses should be repeated when longer data histories from a larger sample of green buildings are available.     

严寒地区既有居住建筑节能改造方案对比分析

分析了乌鲁木齐市既有居住建筑能耗现状,选取1栋典型建筑,并对其进行改造前的能耗计算。在此基础上确定3种改造方案。对改造方案能耗效益、环境效益及投资成本进行了对比评价,为严寒地区既有居住建筑节能改造提供了参考依据。     

武汉市江夏区贺站集镇建筑节能改造实践

以武汉市江夏区贺站集镇综合整治改造工程为例,针对当前既有建筑节能改造过程中由于对建筑能耗数据认识不足导致的节能改造方案一般化、标准化的问题,尝试基于实际能耗构成的重点节能改造思路、措施及方法。     

第三方权威认证及评估机构与节能服务企业在既有建筑节能改造评估中的博弈分析

节能服务企业基于合同能源管理模式实施既有建筑节能改造是我国建筑节能改造事业发展的必然选择.本文通过分析第三方权威认证及评估机构与节能服务企业在既有建筑节能改造市场运行中的行为策略,构建了收益矩阵和博弈模型;考虑第三方权威认证及评估机构与节能服务企业的期望行为和实际行为差异对收益的影响,引入了收益修正函数;提出了第三方权...     

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.     

Energy savings in Danish residential building stock

A large potential for energy savings exists in the Danish residential building stock due to the fact that 75% of the buildings were constructed before 1979 when the first important demands for energy performance of building were introduced. It is also a fact that many buildings in Denmark face comprehensive renovations in the coming years and in connection with this renovation process energy-saving measures can be implemented relatively inexpensive and cost effective. This opportunity should be used to insure the buildings in the future as far as energy consumption is concerned. This paper gives a short account of the technical energy-saving possibilities that are present in existing dwellings and presents a financial methodology used for assessing energy-saving measures. In order to estimate the total savings potential detailed calculations have been performed in a case with two typical buildings representing the residential building stock and based on these calculations an assessment of the energy-saving potential is performed. A profitable savings potential of energy used for space heating of about 80% is identified over 45 years (until 2050) within the residential building stock if the energy performances are upgraded when buildings are renovated.     

Energy retrofit and conservation of a historic building using multi-objective optimization and an analytic hierarchy process

When deciding on the best historic building retrofit,energy savings and thermal comfort can be quantitatively evaluated using an energy model,whereas conservation compatibility is intrinsically qualitative and reflects the perspective of the local heritage authority. We present a methodology that permits finding and comparing optimal retrofits for historic buildings in a multi-perspective and quantitative way. We use an analytic hierarchyprocess to quantify conservation compatibility by distilling a conservation score from the opinions of 10 experts in the field. This score,along with energy needs for heating and cooling and thermal comfort,are the three targets of a multi-objective optimization aimed at identifying optimal retrofits for a medieval building in the north of Italy,destined to become a museum. Retrofit measures considered were different kinds of external and internal envelope insulation,improvement of airtightness,replacement of windows,and ventilative cooling. The result is a portfolio of optimal retrofits that cover the whole range of conservation compatibility. We showthat in the analyzed case heritage preservation is compatible with a four-fold reduction in energy needs at a high thermal comfort level. Even higher energy savings are only achievable at the cost of heritage degradation.