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.     

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.     

Effects of energy retrofits on Indoor Air Quality in multifamily buildings

We assessed 45 multifamily buildings (240 apartments) from Finland and 20 (96 apartments) from Lithuania, out of which 37 buildings in Finland and 15 buildings in Lithuania underwent energy retrofits. Building characteristics, retrofit activities, and energy consumption data were collected, and Indoor Air Quality (IAQ) parameters, including carbon monoxide (CO), nitrogen dioxide (NO₂), formaldehyde (CH₂O), selected volatile organic compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX), radon, and microbial content in settled dust were measured before and after the retrofits. After the retrofits, heating energy consumption decreased by an average of 24% and 49% in Finnish and Lithuanian buildings, respectively. After the retrofits of Finnish buildings, there was a significant increase in BTEX concentrations (estimated mean increase of 2.5 µg/m³), whereas significant reductions were seen in fungal (0.6‐log reduction in cells/m²/d) and bacterial (0.6‐log reduction in gram‐positive and 0.9‐log reduction in gram‐negative bacterial cells/m²/d) concentrations. In Lithuanian buildings, radon concentrations were significantly increased (estimated mean increase of 13.8 Bq/m³) after the retrofits. Mechanical ventilation was associated with significantly lower CH₂O concentrations in Finnish buildings. The results and recommendations presented in this paper can inform building retrofit studies and other programs and policies aimed to improve indoor environment and health.     

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.     

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.     

Assessment of energy and natural resources conservation in office buildings using TOBUS

The potential for optimum energy use and conservation of natural resources in representative southern and northern European office buildings is evaluated using the new European TOBUS methodology and software for office building refurbishment. Various scenarios are being accessed for energy and water conservation in office buildings. The proposed retrofit actions focus in the areas of space heating and cooling, artificial and natural lighting, service hot water, office equipment, elevators and sanitary water. The resulting conservation and related costs are taken into account in order to help the auditor classify the retrofit actions for an audited building. The TOBUS methodology and tools have been implemented to study four Hellenic office buildings and two from Denmark in order to demonstrate the applicability of the overall approach. Energy conservation in Hellenic and Danish buildings range for space heating from 5 to 71 and 0.5 to 6%, for space cooling from 1 to 38 and 4 to 20%, for artificial lighting from 40 to 53 and 26 to 62%, for office equipment from 13 to 62 and 13 to 87% and for elevators at 35 and 23%, respectively. Sanitary water conservation can reach 74% in all audited buildings.     

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.     

The impact of consumer behavior on residential energy demand for space heating

Besides technical parameters, consumer behavior is the most important issue with respect to energy consumption in households. In this paper, the results of a cross-section analysis of Austrian households are presented. The impact of the following parameters on residential energy demand for space heating have been investigated: (i) thermal quality of buildings; (ii) consumer behavior; (iii) heating degree days; (iv) building type (singleor multi-family dwellings). The result of this investigation provides evidence of a rebound-effect of about 15 to 30% due to building retrofit. This leads to the conclusion that energy savings achieved in practice (and straightforward the reduction in CO₂ emissions) due to energy conservation measures will be lower than those calculated in engineering conservation studies. Straightforward, the most important conclusions for energy policy makers are: (i) Standards, building codes, respectively, are important tools to increase the thermal quality of new buildings; and (ii) Due to prevailing low energy prices, a triggering tool has to be implemented which may be rebates or loans.     

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.     

Measuring residential duct efficiency with the short-term coheat test methodology

Assessing the thermal efficiency of a forced-air distribution system is difficult, in large part because of interactions between energy loss mechanisms and other building characteristics. This paper describes short-term coheating, a method of measuring the thermal efficiency of residential heating and cooling distribution systems in situ, and presents the results of a series of studies that utilized the short-term coheat methodology. Short-term coheat tests were conducted in 53 residential buildings including both site-built and manufactured housing. The magnitude of the distribution efficiency, defined as the ratio of the energy required to heat the building if there were no duct losses to the actual heating energy required, ranged from less than 50% for homes with disconnected ducts to more than 90% for well sealed and insulated systems. Duct retrofits were also performed at 20 of the test sites and, following the retrofits, on average, the homes required 16–17% less heating energy. These results show that residential distribution system losses can be responsible for substantial energy loss and that duct retrofits are a viable energy conservation strategy for homes with distribution systems located outside of the conditioned space.     

Impacts of building operational schedules and occupants on the lighting energy consumption patterns of an office space

This paper considers pre-retrofit and post-retrofit lighting energy end-use of two sub-metered office spaces. Building lighting retrofits are typically installed to reduce energy consumption and operational costs of buildings. This traditionally includes replacing lights and introducing Building Management System (BMS). Through this process, an occupant’s ability to override new computerized controls could be compromised, which can dramatically affect the overall success of the project. Therefore, the analysis focuses on the effectiveness of the lighting retrofit, influence of the BMS upgrade, occupant behavior, and the lessons learned. The analysis comprises three different phases including one pre-retrofit and two post-retrofit phases. Each of the retrofit phases lasted approximately one year, leading to the monitoring of three years of sub-metered lighting energy end-use. The results showed that when the occupants had access to the lighting switches while BMS managed the operational lighting schedule, the office area with the responsible occupant saved 23.2% compared to the pre-retrofit phase. For the second lighting retrofit phase when the occupants did not have access to the light switches, the lighting schedule operated for more than two hours after the typical work day and the occupant was not able to turn off the lights upon departure. It should be noted that there are limited numbers of studies that consider three years sub-metered lighting retrofit data with the presented granularities in this study. Similar lighting retrofit projects could benefit from the findings of this study. Finally, the results of this sub-metered lighting data could address uncertainty in the selection of lighting power density and associated schedules of building energy simulations.     

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.     

Cost-benefit analysis and emission reduction of lighting retrofits in residential sector

This study projects electricity savings, cost-benefit analysis and emission reduction of lighting retrofits in Malaysia residential sector. The cost-benefit is determined as a function of energy savings due to retrofit of more efficient lighting system. The energy savings were calculated based on 25, 50 and 75% of potential retrofits of inefficient lighting in residential sector. The study found that, this strategy save a significant amount of energy and consumers money. However, an effort to create energy efficiency awareness among consumers and subsidies efficient lighting should be identified, because this efficient lighting is quite expensive in Malaysia.     

Energy-savings predictions for building-equipment retrofits

Energy-consumption data collected from two equipment-retrofit projects before and after the retrofits was used to develop a model that estimates energy savings from retrofit projects. The computation method used in the model is based on Artificial Neural Networks (ANN). The model integrates weather variables, specific equipment-usage and occupancy data, and building-operation schedules into the pre-retrofit energy-usage pattern. It then estimates the energy usage of the pre-retrofit equipment in the post-retrofit period by using weather data, occupancy, and building-operation schedules in the post-retrofit period. The difference between the recorded energy usage of the post-retrofit equipment and the predicted energy usage of the pre-retrofit equipment in the post-retrofit period is the estimate of energy savings. For the two retrofit projects used in the ANN model, the coefficient of correlation varied from 0.957 to 0.844; the root mean square error varied from 6.81% to 16.4%; and the mean absolute error varied from 5.31% to 9.95%. Additionally, the sensitivity of the model to the input variables was analyzed with one of the retrofit project data. Dry bulb temperature, wet bulb temperature, and time (representing building-occupancy and equipment-operation schedule) were determined as the most effective variables in the ANN model. The research and findings are presented in this paper.     

Energy conservation and retrofitting potential in Hellenic hotels

Energy consumption data from 158 Hellenic hotels and estimated energy savings that result from the use of practical retrofitting techniques, materials and new energy efficient systems are presented. The data were collected during an extensive energy audit of buildings that was carried out in Hellas, within the frame of a National Energy Programme sponsored by the CEC VALOREN Programme, for energy conservation in buildings. During this short monitoring campaign and on-site visits of a trained panel of engineers to each building, all information related to the building's construction, heating, cooling and lighting systems, and all other mechanical and electrical systems, was collected. The main results and energy characteristics of cooling, heating and lighting on energy consumption and performance are discussed. The annual average total energy consumption in hotels is 273 kWh/m², one of the highest among all categories of buildings. Several scenarios for possible interventions to the building's outer envelope, heating, cooling and lighting systems are proposed and evaluated, in order to assess the effectiveness of various energy conservation techniques. Based on the results from several simulations, it is concluded that it is possible to reach an overall 20% energy conservation.     

Residential energy use and conservation in Sweden

We describe energy use in Swedish homes from 1963 to 1980 using data assembled and analyzed for the first time. Changes in energy use by fuel and purpose before and after the 1973 oil price shock are illustrated and discussed, and savings in space heating in the year 1980, compared with the pre-embargo period, are quantified. We discuss two important elements of Swedish energy conservation policy, the building codes and the system of grants and loans to homeowners. We conclude that the grants and loans probably accelerated home retrofit measures, while the building codes will play an important role in reducing residential heat losses over the long term.     

A two-thirds reduction in the space heat requirement of a Twin Rivers townhouse

A Twin Rivers townhouse received a series of retrofits more extensive than those deployed in previous experiments at Twin Rivers, and a 67% reduction in annual energy use for space heating resulted. The retrofits included interior window insulators of various designs, basement and attic insulation and systematic attention to routes of air infiltration. The 67% reduction was approximately the savings anticipated by a simple model, in which the “second role” of insulation in improving the retention of the non-furnace heat from sun, appliances, and people appears explicitly. (In the absence of non-furnace heat, the savings of gas achieved would have been only 50%.) The retrofits appear to be a financially attractive investment at the present price of natural gas and a 10% return on investment. Further retrofits are discussed.     

上海医院建筑节能改造案例分析

医院建筑是公共建筑中能耗最高的建筑类型.在国家节能减排的大环境下,医院建筑的节能研究相对滞后,医疗主管部门急需了解医院建筑的实际能耗水平和节能潜力,并在此基础上制定相应的能耗考核指标.本文介绍了上海市医院建筑节能改造专题研究和实施试点工作中3家三级甲等医院的节能改造案例,通过对这3家医院节能改造效果进行分析,总结了存在的问题和经验,为医院建筑的相关节能改造工作提供参考.     

Transformative change: energy-efficiency and social housing retrofits in Canadian cities

The article provides the first comparative assessment of the energy-efficiency retrofit programs in social housing of the largest cities in Ontario, British Columbia and Alberta, focusing on program efficiency and effectiveness. The analytical framework explores key policy instruments – regulatory, fiscal and institutional – in relation to major results achieved. In terms of efficiency, the grant programs were highly relevant, timely and successful in meeting their objectives generating improvements in two-thirds of the social housing in Toronto, Vancouver and Calgary. The effectiveness was moderate, with targeted approaches to retrofits, integrating both mechanical and building envelope measures with high potential for energy savings. One of the greatest challenges was the high cost of the program, the lack of sustainability in funding and and the cost recovery of comprehensive retrofits..     

Optimum insulation thicknesses for building walls with respect to cooling and heating degree-hours in the warmest zone of Turkey

Thermal insulation is one of the most effective energy conservation measures for cooling and heating in buildings. Therefore, determining and selecting the optimum thickness of insulation is the main subject of many engineering investigations. In this study, the determination of optimum insulation thickness on external walls of buildings is comparatively analyzed based on annual heating and cooling loads. The transmission loads, calculated by using measured long-term meteorological data for selected cities, are fed into an economic model (P₁−P₂ method) in order to determine the optimum insulation thickness. The degree-hours method that is the simplest and most intuitive way of estimating the annual energy consumption of a building is used in this study. The results show that the use of insulation in building walls with respect to cooling degree-hours is more significant for energy savings compared to heating degree-hours in Turkey's warmest zone. The optimum insulation thickness varies between 3.2 and 3.8 cm; the energy savings varies between 8.47 and 12.19 $/m²; and the payback period varies between 3.39 and 3.81 years depending on the cooling degree-hours. On the other hand, for heating load, insulation thickness varies between 1.6 and 2.7 cm, energy savings varies between 2.2 and 6.6 $/m², and payback periods vary between 4.15 and 5.47 years.