Operational Energy Use Research Articles

Characterising the English school stock using a unified national on-site survey and energy database

The recent commitment towards a net-zero target by 2050 will require considerable improvement to the UK’s building stock. Accounting for over 10% of the services energy consumption of the United Kingdom, the education sector will play an important role. This study aims to improve the understanding of English primary and secondary schools, using national on-site survey data with several large-scale disaggregate data sources. Property Data Survey Programme (PDSP) data on 18,970 schools collected between 2012 and 2014, Display Energy Certificate (DEC) and school census data from the same period were linked and processed to form a unified schools dataset. Statistical analyses were undertaken on 10,392 schools, with a focus on energy performance, and the relationship to several building and system characteristics. The analyses may point to the possibility of assessing operational energy use of schools in a more disaggregate manner. New datasets with detailed and accurate disaggregate information on characteristics of buildings, such as those used in this study, provide opportunities to develop more robust models of the building stock. Such data would provide an opportunity to identify pathways for reducing carbon emissions effectively and provide lessons for other organisations seeking to achieve significant reductions for achieving climate change goals. Practical Application: Outputs from this study are expected to benefit researchers in various organisations to establish a basis for typical buildings and their performance, facilities managers to assess the operational energy efficiency of school buildings, and relevant public bodies to make informed decisions on improving energy efficiency of the school stock.

Estimation of Carbon Footprint of Residential Building in Warm Humid Climate of India through BIM

In recent years Asian Nations showed concern over the Life Cycle Assessment (LCA) of their civil infrastructure. This study presents a contextual investigation of a residential apartment complex in the territory of the southern part of India. The LCA is performed through Building Information Modelling (BIM) software embedded with Environmental Product Declarations (EPDs) of materials utilized in construction, transportation of materials and operational energy use throughout the building lifecycle. The results of the study illustrate that cement is the material that most contributes to carbon emissions among the other materials looked at in this study. The operational stage contributed the highest amount of carbon emissions. This study emphasizes variation in the LCA results based on the selection of a combination of definite software-database combinations and manual-database computations used. For this, three LCA databases were adopted (GaBi database and ecoinvent databases through One Click LCA software), and the ICE database was used for manual calculations. The ICE database showed realistic value comparing the GaBi and ecoinvent databases. The findings of this study are valuable for the policymakers and practitioners to accomplish optimization of Greenhouse Gas (GHG) emissions over the building life cycle.

Overview and Main Findings for the Austrian Case Study

As part of a project investigating in the potential greenhouse gas mitigation effect of the increased use and production of mass timber worldwide, a comparative study was carried out to show the potential benefit of mass timber use in buildings in central Europe. After designing a mass timber building functionally equivalent to an existing conventional building, cradle to grave life cycle assessments (LCA) were calculated. The reference is an eight-story building with mixed use in Vienna, originally built in reinforced concrete. Global Warming Potential (GWP) is defined as the central parameter of interest. Calculated life cycle phases are A1–A3 (resource to production), A4 and A5 (transport to site and construction, respectively), B4 (replacement in the use phase), and C1–C4 (End of Life), as well as D (benefits and loads beyond the building life). It can be shown that the total mass of the timber building is 47% lower than of the concrete building. Considering life cycle phases A1 to A5, the timber building shows 18% less embodied carbon. Taking the whole building life cycle and the operational energy use (B6) into account, differences in GWP are much lower, as the heating system, though equipped with high efficiency and clean Austrian electricity grid mix, has much higher impact than the other phases.

A comparative life cycle assessment between green walls and green facades in the Mediterranean continental climate

The building and construction sector is a large contributor to anthropogenic greenhouse gas emissions and consumes vast natural resources. Improvements in this sector are of fundamental importance for national and global targets to combat climate change. In this context, vertical greenery systems (VGS) in buildings have become popular in urban areas to restore green space in cities and be an adaptation strategy for challenges such as climate change. However, only a small amount of knowledge is available on the different VGS environmental impacts. This paper discusses a comparative life cycle assessment (LCA) between a building with green walls, a building with green facades and a reference building without any greenery system in the continental Mediterranean climate. This life cycle assessment is carried according to ISO 14040/44 using ReCiPe and GWP indicators.Moreover, this study fills this gap by thoroughly tracking and quantifying all impacts in all phases of the building life cycle related to the manufacturing and construction stage, maintenance, use stage (operational energy use experimentally tested), and final disposal. The adopted functional unit is the square meter of the facade. Results showed that the operational stage had the highest impact contributing by up to 90% of the total environmental impacts during its 50 years life cycle. Moreover, when considering VGS, there is an annual reduction of about 1% in the environmental burdens. However, in summer, the reduction is almost 50%. Finally, if the use stage is excluded, the manufacturing and the maintenance stage are the most significant contributors, especially in the green wall system.

Forced to be green? The performance impact of energy-efficient systems under institutional pressures

With institutional pressures from various stakeholders concerned with climate change and efficient energy use in firms' operations, it has formed the belief that energy efficiency is crucial part for sustainable operations and firm competitiveness. While an increasing number of firms have adopted energy-efficient systems (EES), a limited understanding of the actual impact of EES adoption on financial performance and how institutional pressures moderate that impact remains. Based on 238 listed firms that have deployed EES, the study reveals that firms improve their return on assets (ROA), and different institutional pressures have significant and diverse effects on the performance of EES adoption. While pressures imposed by government policies and environmental non-government organizations (NGOs) provide less financial benefits of EES, pressures from competitors provide more financial benefits of EES. The research provides empirical evidence of how pressures from energy efficiency policies, environmental groups, and competitors affect the EES-performance relationship. We also discuss implications of the findings for managers, public policymakers, NGOs, and academia.

Homeowner low carbon retrofits: Implications for future UK policy

The promotion of low-carbon home retrofit among UK homeowners is widely recognised as an important strategy to reduce operational energy use in dwellings and mitigate climate change. The related predominant UK policy approach is to address various market failures and develop the market for low-carbon retrofit and innovation. The current low uptake rate of low-carbon home retrofit suggests that a complementary policy approach is necessary to increase it and support households in their change towards low-carbon living. This paper uses an innovation framework to analyse retrofit as an innovation-decision process of several stages. Low-carbon technology is conceptualised at three nested levels: product, design option and technological system. A multiple-case study approach is used to analyse eight home retrofit cases from the SuperHomes network, that achieved significant carbon emission reductions through retrofit activities. Case analysis shows that: (i) homeowners collect information for each technology level through different communication channels, which are not interchangeable; (ii) homeowners develop a certain capacity to transform their environmental concerns into substantial retrofit activities; (iii) the positive retrofit experience of homeowners is crucial to develop such capacity and to convince others to retrofit their homes. These findings have important implications for energy policy on retrofit uptake in UK to support household transition to low-carbon living.

2019 energy benchmarking data for LEED-certified buildings in Washington, D.C.: Simulation and reality

This study aims to understand the actual performance difference between LEED buildings and non-LEED buildings. Since 2012, the District of Columbia (DC) has amended regulations so that all buildings must report their building energy use. We have cross-referenced the most recently published data of the 2019 DC energy benchmarking database with the U.S. Green Building Council's LEED project database to identify DC properties in both databases that are expected to reduce building operating energy use and greenhouse gas emissions. We compared LEED office buildings and non-LEED-certified office buildings using their reported operating source and site energy use intensity (EUI). The results show that LEED office buildings do not perform better at any of the certified levels. On the contrary, those reported LEED buildings collectively use 17% more source energy and 13% more site energy than non-LEED buildings. Among the different LEED levels, LEED Silver appears to perform slightly better than the other LEED levels. Meanwhile only around 33% of qualified LEED office buildings reported their actual energy use according to the DC regulation. The purpose of this study is not to criticize the LEED rating system; instead, we want to improve the system in order to meet DC's carbon neutrality goal. To this extent, we conclude that the U.S. LEED rating system can benefit from learning from other green building rating systems that include reporting and verification as prerequisite requirements.

Evaluation of Life-Cycle Assessment Analysis: Application to Restoration Projects and New Construction in Alpine Climate, Japan

The present paper discusses the applications of life-cycle assessment (LCA) to construction works in Japan. LCA has been frequently used to assess the environmental impacts of new construction. Nonetheless, the applications of LCA to restoration have not been fully confirmed to date. It is said that historical buildings may contribute to sustainable development. Nonetheless, as for heritage buildings, since the protection of cultural value is usually prioritised, their environmental impacts may not be sufficiently explored. To this aim, this paper evaluated the environmental impacts of the restoration of heritage buildings. This paper consisted of two tasks. First, the restoration projects of heritage buildings in Japan were introduced. The restoration of two heritage houses was discussed, referring to heritage protection legislation in Japan. Second, LCA was performed on the restoration of heritage houses and the construction of contemporary houses. Environmental impacts were compared between the restoration and new construction with regard to greenhouse gas emissions and operational energy use. A focus was given to the amount of materials used. Restoration consumes a limited amount of materials compared to new construction, although the energy use of heritage buildings is considerable. The environmental impacts of restoration were quantified so that they were compared with those of new construction. The comparison indicated issues applying LCA to heritage buildings.

Comfort within Budget: Assessing the Cost-Effectiveness of Envelope Improvements in Single-Family Affordable Housing

In Brazil, the delivery of homes for low-inc ome households is dictated by costs rather than performance. Issues such as the impact of climate change, affordability of operational energy use, and lack of energy security are not taken into account, even though they can severely impact the occupants. In this work, the authors evaluated the thermal performance of two affordable houses as-built and after the integration of envelope improvements. A new replicable method to evaluate the cost-effectiveness of these improvements was proposed. The case study houses comprise the most common affordable housing type delivered widely across Brazil and a proposition of a better affordable housing solution, built in Porto Alegre, southern Brazil, integrating passive design strategies to increase thermal comfort. The findings reveal a potential for improving indoor thermal conditions by up to 76% and 73%, respectively, if costs are not a concern, and 40% and 45% with a cost increase of 12% and 9% if a comfort criterion of 20–25 °C was considered. Equations to estimate costs of improvements in affordable housing were developed. The authors concluded that there is a great scope for building envelope optimisation, and that this is still possible without significant impact on budget.

Integrating long term temporal changes in the Belgian electricity mix in environmental attributional life cycle assessment of buildings

The operational energy use is responsible for an important share of the life cycle environmental impact of buildings. In the national LCA method for buildings in Belgium, as in most environmental impact assessments, operational energy use and associated impacts are kept unchanged throughout the 60-year service life of the building. The energy mix will however change over the building life cycle and this will influence the impact of the operational energy use. The overall aim of this paper is to analyse how long term temporal changes in the electricity mix in Belgium might influence the life cycle environmental impact of buildings using an attributional approach. This paper focuses on three aspects. First, it analyses future scenarios for the Belgian electricity mix as it is uncertain how it will change over time. Second, the environmental impact of these changes in the mix is evaluated using the Belgian life cycle impact assessment method for buildings considering a broad set of indicators. Finally, it is investigated how these changes in the electricity mix during the building service life can be included in the attributional life cycle assessment and how this influences the overall environmental impact of the operational phase. Within this study, three dynamic scenarios are defined and compared with the static approach, i.e. current electricity mix remains unchanged during the next 60 years. The analysis reveals differences in the building life cycle environmental impact of −29% and +34% compared to the current static approach, while differences in the life cycle carbon footprint range from −59% to +33%. This highlights the importance of considering changes in the electricity mix in LCA of buildings and in considering a broad range of environmental indicators instead of solely focussing on greenhouse gas emissions when making policy decisions. In general, a major challenge for the next decade seems to be phasing out nuclear power, without increasing the environmental impact of the electricity mix.

Environmental Impact Assessment of Renovated Multi-Apartment Building Using LCA Approach: Case Study from Lithuania

In Europe, more than 75% of buildings are energy inefficient according to current energy standards. These buildings account for 40% of total energy consumption. Therefore, addressing the energy efficiency of existing buildings through various renovation measures remains of critical importance. In this study, two differently renovated multi-apartment buildings were selected to evaluate its environment impact using life cycle assessment. The buildings were built during the early 1980s, which did not meet the current energy efficiency standards. In recent times, these buildings were revised by Governmental agencies through the modernization process. The aim of the assessment is to study the environmental impacts associated with different renovation measures that has been carried out. This assessment covers the impact of new materials added, and the operational energy use. The study reveals that renovation stage accounts for 19% CO2 emission. The renovated buildings with renewable measures have a significant impact over climate change than the conventional renovation measures. Moreover, the potential savings in thermal energy used for space heating and domestic hot water preparation are 25% and 40% after conventional and renewable measures renovation, respectively. It was concluded that the total climate change potential could be reduced from 12% and 48% by retrofitting combined with renewable energy measures.

Learnings from Developing a Context-Specific LCA Tool for Buildings—The Case of LCAbyg 4

Buildings are a major cause of global resource consumption, greenhouse gas (GHG) emissions and other impacts on the environment, originating from both operational energy and material use. Informed design decisions can help mitigate potential impacts on the environment, by the use of life cycle assessment (LCA) in the early project stages. In order to mitigate building environment impacts throughout the industry, architects and engineers need tools that are integrated in the design workflow and based on the information available. Existing LCA tools for building design professionals are predominantly embedded in a specific context such as a country or a sustainability scheme. This paper provides learnings for the development of context-tailored tools for building-LCA using the case of Denmark, with specific focus on GHG-emissions that are in focus worldwide. Based on stakeholder involvement, four key areas were defined: Default information, flexibility, environmental design feedback and transparent results. Tool functions include a component library and a quantity estimator for bridging incomplete building information. A comparison monitor displays the performance of design solutions selected in the model, while a number of graphs and tables provide analysis of inventory and results. Finally, a customisable model data export, a complete input/output file for revision and custom analysis are among key functions for transparency.

How to define (net) zero greenhouse gas emissions buildings: The results of an international survey as part of IEA EBC annex 72

The concept of (net) zero greenhouse gas (GHG) emission(s) buildings is gaining wide international attention and is considered to be the main pathway for achieving climate neutrality targets in the built environment. However, there is an increasing plethora of differing terms, definitions, and approaches emerging worldwide. To understand the current progress of the ongoing discussion, this study provides an overview of terms, definitions, and key features from a review of 35 building assessment approaches. The investigation identified that 13 voluntary frameworks from 11 countries are particularly characterised by net zero-carbon/GHG emissions performance targets, which are then subject to a more detailed analysis. The review was organised in the context of the project IEA EBC Annex 72 on “Assessing Life Cycle Related Environmental Impacts Caused by Buildings”, which involves researchers from over 25 countries worldwide.In the current dynamic political surroundings and ongoing scientific debate, only an initial overview of this topic can be presented. However, providing typologies and fostering transparency would be instrumental in delivering clarity, limiting misunderstanding, and avoiding potential greenwashing. To this end, this article categorises the most critical methodological options—i.e., system boundaries for both operational and embodied GHG emissions, the type of GHG emission factor for electricity use, the approach to the “time” aspect, and the possibilities of GHG emission compensation—into a comprehensive framework for clarifying or setting (net) zero GHG emission building definitions in a more systematic way.The article concludes that although variations in the existing approaches will continue to exist, certain minimum directions should be considered for the future development of harmonised (net) zero GHG emissions building frameworks. As a minimum, it is recommended to extend the usual scope of the operational energy use balance. At the same time, minimum requirements must also be set for embodied GHG emissions even if they are not considered in the carbon/GHG emissions balance.

Analysis of the embodied energy of construction materials in the life cycle assessment of Hellenic residential buildings

As the operational energy use in new constructions is moving towards nearly zero energy buildings, the embodied energy of buildings is gaining more importance. This work elaborates the importance of embodied energy in Hellenic residential buildings by comparing the primary energy consumption during their life cycle. Field surveys were used to collect relevant data from local manufactures and determine the embodied energy coefficients of popular construction materials. The derived embodied energy intensities (EEI) and the calculated primary energy use intensities (EUI) are then used for benchmarking the buildings’ energy and environmental life cycle performance. The EEI value ranged from 3.2 to 7.1 GJ/m2, compared with annual primary EUI of 0.3 to 3.9 GJ/m2. The initial and recurrent embodied energy of building construction materials over the lifetime of a building can reach up to ~30%. The analysis quantified the time it takes for the operational energy savings resulting from energy conservation measures that are implemented in existing dwellings to recover the embodied energy impact of the new materials or products that are used. For individual measures, the average recovery time ranged from 1 to 6 years, and up to 10 years from more conservative estimates. For a combined scenario it approaches ~2 years or ~3.5 years, respectively.

Interoperable IoT system that could adapt local context of the built environment

IoT technology has great potential to transform the built environment and, in doing so, create energy savings. With operational energy use in buildings causing around 30 per cent of CO2 gas emissions, and demand for energy use in buildings on the rise, it is necessary to develop measures to reduce consumption, and IoT could hold the key to this. Just a few examples of ways that this can be achieved are: real-time energy monitoring, with IoT smart sensors measuring the power consumption of a building to show how and where energy is used; smart lighting, whereby unnecessary lighting is switched off and energy saved; and smart metering systems, leading to higher energy efficiency, cost savings and new data sources. Indeed, IoT devices in buildings can collect important data, which has a number of important applications, and the long-term value of IoT devices in buildings comes from mining the data collected by sensors and devices as this can be used to enhance building performance and efficiency. Professor Tomonari Yashiro, based at the Institute of Industrial Science, The University of Tokyo, is exploring how ICT and the IoT could help improve the sustainability and energy efficiency of buildings.

The global energy footprint of information and communication technology electronics in connected Internet-of-Things devices

Information and communication technology (ICT) has been critical to the emergence of a new Internet-of-Things (IoT) era, as a rapidly increasing number and variety of IoT electronic devices in a wide range of end-use sectors require massive data communication in terms of volume, velocity/speed, and variety. Semiconductor technology advancements have played a key role in ICT and unlike the past ICT energy footprint analysis, which focused on the final electronic product, an attempt has been made to examine the global energy impacts for the period 2016–2025 based on the market forecasts of three major IoT IC types, i.e., sensors and actuators, connectivity, and processor ICs distributed among four major IoT device components. Total global IoT semiconductor primary energy demand is projected to increase from 2 EJ in 2016 to 35 EJ by 2025, resulting mainly from a substantial projected increase energy needed in the manufacturing of ICs, with growth in the use of sensors and energy-intensive next fab generation manufacturing. Unlike the trend in manufacturing energy, total global operational energy use is projected to decrease significantly with the development of smaller transistor size, low-power devices, and faster wireless data communication technology. Total operational energy is projected to significantly decrease from 118 TWh/year (1,2 EJ/year) to less than 1 TWh/year (0.003 EJ/year) in spite of a significantly higher anticipated growth in its market size during the 2016–2025 forecast period. Its annual share of total primary energy use is projected to reach an insignificant level of 0.01% by the end of 2025, consistent with the past limited electronic product life cycle analyses besides the analysis focus here limited to ICs in IoT devices.

Upscaling the housing renovation market through far-reaching industrialization

The European existing building stock contributes to 40% of the total energy use and 36% of the CO2 emissions. To deal with the climate crisis, European climate and energy objectives were defined. By 2050, CO2 emissions should be cut to 80-95% compared to 1990 and all buildings must be energy-neutral. The North-Sea Region alone consists of 22 million outdated dwellings built between 1950 and 1985 that are in high need of renovation. Nowadays, the renovation industry applies mainly manual on-site renovation techniques, resulting in a low renovation pace, relatively high labour costs and a long duration. To tackle the urgent need for rapid renovations, six countries of the North-Sea Region collaborate to upscale the current renovation process in the Interreg project INDU-ZERO “Industrialization of house renovations toward energy-neutral”. The project focuses on modular prefabricated renovation packages with fully integrated HVAC technologies to arrive at energy-neutral dwellings. The project researches the possibilities of far-reaching automated and industrialized production processes. A smart factory blueprint will be designed to speed up the renovation pace to a target of 15,000 renovation packages per year per factory while cutting the current price with 50%. This contribution focusses on three main topics: material use, operational energy use and transport. Firstly, the reasoning behind the renovation package design is explained. Next, the packages are adopted on an archetype dwelling to document the thermal performance before and after renovation. Finally, the associated logistics are studied. To summarize each individual research in a blanket result, the environmental impact is determined and compared to the non-renovated dwelling.

Performance Analyses of Temperature Controls by a Network-Based Learning Controller for an Indoor Space in a Cold Area

For the sustainable use of building spaces, various methods have been studied to satisfy specific conditions required by the characteristics of space types and the energy use in operation. However, several effective control approaches adopting the latest statistical tools may have problems such as higher control precision increases energy consumption, or lower energy consumption decreases their control precision. This study proposes an optimized model to reach the indoor set-point temperature by controlling the amount of heating supply air and its temperature and investigates the efficiency of an adaptive controller to maintain indoor thermal comfort within setting ranges. In the consistency of the comfort level, the fuzzy logic controller was found to be 1.76% and the artificial neural network controller to be 17.83%, respectively, more efficient than the conventional thermostat. In addition, for energy use efficiency, both of the controllers were confirmed to be over 3.0% more efficient. Consequently, the network-based controller with the adaptive controller checking comfort levels effectively works to improve both energy efficiency and thermal comfort. This improvement can be significant in places such as commercial high-rises, large hospitals, and data centers where many spaces are intensively woven with appropriate thermal environments to maintain users’ workability.

Achieving net zero life cycle primary energy and greenhouse gas emissions apartment buildings in a Mediterranean climate

Achieving net zero life cycle energy and greenhouse gas emissions buildings is rare. This would entail not only covering operational energy use, but also embodied energy and displacing embodied greenhouse gas emissions in construction materials and renewable energy systems, across their supply chains.The aim of this paper is to evaluate the feasibility of achieving net zero life cycle primary energy and greenhouse gas emissions (NZLCPEGHG) buildings. We use a case study apartment building in Sehaileh, Lebanon and conduct a life cycle cost, energy and greenhouse gas emissions analysis over 50 years of a business-as-usual building and its NZLCPEGHG counterpart.Results show that a 6.5 kWp solar photovoltaic array, solar hot water, an improved operational energy efficiency, an all-electric operational energy demand, and a reduced embodied energy, can achieve a NZLCPEGHG apartment unit (154 m2, 4 occupants) in a four-storey building. Installing battery storage (or not) is critical regarding life cycle cost, swinging the net present value from −46 to +47 USD2020/(m2-of-gross-floor-area) over 50 years. The greenhouse gas emissions factor of the electricity grid is key to achieving a NZLCPEGHG building, with cleaner grids making it harder to displace embodied greenhouse gas emissions. We argue, inter alia, for a more transparent and comprehensive definition of NZLCPEGHG buildings, policy that subsidises this level of performance to cover additional capital costs, and reducing the initial embodied energy and greenhouse gas emissions that might never be paid-back or displaced. These measures will help address the current climate emergency.

Multi-Objective Optimization of Building Life Cycle Performance. A Housing Renovation Case Study in Northern Europe

While the operational energy use of buildings is often regulated in current energy saving policies, their embodied greenhouse gas emissions still have a considerable mitigation potential. The study aims at developing a multi-objective optimization method for design and renovation of buildings incorporating the operational and embodied energy demands, global warming potential, and costs as objective functions. The optimization method was tested on the renovation of an apartment building in Denmark, mainly focusing envelope improvements as roof and exterior wall insulation and windows. Cellulose insulation has been the predominant result, together with fiber cement or aluminum-based cladding and 2-layered glazing. The annual energy demand has been reduced from 166.4 to a range between 76.5 and 83.7 kWh/(m2 y) in the optimal solutions. The fact that the legal requirements of 70 kWh/(m2 y) are nearly met without building service improvements indicates that energy requirements can be fulfilled without compromising greenhouse gas emissions and cost. Since the method relies on standard national performance reporting tools, the authors believe that this study is a preliminary step towards more cost-efficient and low-carbon building renovations by utilizing multi-optimization techniques.