Retrofit Measures Research Articles

Supportive governance for city-scale low carbon building retrofits: a case study from Shanghai

ABSTRACT There is significant potential for reducing energy use and emissions from buildings through energy efficiency retrofits. However, a number of barriers, including long payback periods and uncertainties around business models and technologies, restrict large scale implementation. A recent joint project, piloting green energy schemes and low-carbon investments in public and commercial buildings in the Changning district of Shanghai, China, indicated opportunities to break through these barriers. This study conducted a cost benefit analysis to investigate how an innovative combination of financial and non-financial supported retrofits, and could serve as a model for other urban areas. In total, 44 retrofit sub-projects were carried out and achieved energy savings of 30,217 tons of coal equivalent. The average payback period was 2.43 years, and with subsidies was further reduced to 1.79 years. The Changning Low Carbon Office played a critical role in coordinating and supporting the uptake of retrofit measures but non-economic factors continue to restrict investment by financial institutions and the implementation of retrofits on a larger scale. Key policy insights Public and commercial building retrofits in Shanghai are found to generate commercially acceptable payback periods while having achieved significant energy and emissions reductions. Subsidies from the city and district governments significantly reduced the payback periods of energy efficiency retrofits, but may also crowd out investment by financial institutions. The Changning Low Carbon Office has coordinated energy efficiency retrofitting efforts, provided access to information, helped to connect investment funds with project opportunities and support project management. Achieving the deeper retrofits needed to achieve China’s climate targets may require more substantial financial incentives.

COMPARATIVE SEISMIC PERFORMANCE ASSESSMENT OF UHPC JACKETING AND SCED BRACING TECHNIQUES

Observed damage to existing pre-seismic code buildings in previous earthquakes has raised interest among the engineering community for improving the performance of these structures using different seismic retrofit measures. This paper throws light on contemporary techniques for the seismic retrofit of RC buildings, namely ultra-high-performance concrete (UHPC) jacketing and self-centering energy dissipative (SCED) braces. Detailed fiber-based numerical modeling of a benchmark structure is undertaken to evaluate the effectiveness of the selected retrofit measures. The case study structure is a two-story pre-seismic code residential building designed for gravity and wind loads, exhibiting poor seismic performance. Along with the two retrofit strategies investigated, several parameters are also considered. Inelastic static pushover and incremental dynamic analyses are conducted to select the retrofit measures and assess their effects on seismic performance. Using a collection of far-field earthquake records and a set of performance criteria, fragility functions are constructed to assess the vulnerability of the benchmark structure with and without the retrofit solutions. The study shows that the adopted index that links cost to the seismic performance obtained from the fragility functions can provide a rational ranking of the selected retrofit approaches relative to the existing building and support selecting the most effective and economical alternative.

Structural Repair/Retrofit of Brick Masonry Walls

The various methods presently available for the repair of brick masonry walls are reviewed. Particular attention is given to structural repair made necessary as the result of earthquake induced damage or retrofit measures to be applied to an existing masonry structure to increase seismic resistance. Among the techniques discussed are: crack injection with epoxy or resin, crack or void injection with a cement based grout, surface coating methods, base isolation, repointing or limited replacement of damaged elements and installation of steel reinforcing elements. Use of nondestructive evaluation methods to determine the initial damaged state and the condition of the repaired masonry wall will also be presented.

Evaluation of the aircraft fuel economy using advanced statistics and machine learning

Fuel represents a significant proportion of an airline’s operating costs. Statistical analyses and physical models have been used to monitor and estimate fuel consumption up to now, but these can have considerable inaccuracies. This means that, currently, there are no suitable detection methods for the evaluation of aircraft retrofits, of which some only suggest a fuel efficiency potential in the tenths of a percent range. This article examines suitable assessments of the fuel economy of aircraft and especially aircraft with and without retrofitting. For this purpose, the effects of technical influences such as measurement errors and external uncertainties such as turbulence on the evaluation of the fuel economy are examined in more detail. The focus of the article is on a discussion of possible optimization potentials of conventional statistical evaluation methods, especially regarding possible misinterpretations and spurious correlations. This discussion is exemplarily based on a case study of simulated flight data of an Airbus A320 (with and without improved wing tips (sharklets) as an exemplary retrofit). For this purpose, a suitable simulation environment is presented in which relevant environmental parameters such as wind and turbulence can be set, and measurement errors in the recorded data can be manipulated. It is found that measurement errors as well as turbulence can lead to a bias in key figures that are used for the evaluation of fuel flow signals. The effect of turbulence can partly be mitigated by the use of an improved key figure the authors propose. The investigation is also carried out using a data-based evaluation method to simulate the fuel flow using a machine learning model (random forests), whereby the effects of turbulence and measurement errors significantly influence the fuel flow predicted by the model in the same order of magnitude as potential retrofit measures.

Energy-Efficient Retrofit Measures (EERM) in Residential Buildings: An Application of Discrete Choice Modelling

Cross-country evidence on the adoption of energy-efficient retrofit measures (EERMs) in residential buildings is critical to supporting the development of national and pan-European policies aimed at fostering the energy performance upgrade of the building stock. In this light, the aim of this paper is to advance in the understanding of the probability of certain EERMs taking place in eight EU countries, according to a set of parameters, such as building typology, project types, and motivation behind the project. Using these parameters collected via a multi-country online survey, a set of discrete-choice (conditional logit) models are estimated on the probability of selecting a choice of any combination of 33 EERMs across the sampled countries. Results show that actions related to the building envelope are the most often-addressed across countries and single building elements or technology measures have a higher probability of being implemented. The modelling framework developed in this study contributes to the scientific community in three ways: (1) establishing an empirical relationship among EERMs and project (i.e., retrofit and deep retrofit), (2) identifying commonalities and differences across the selected countries, and (3) quantifying the probabilities and market shares of various EERMs.

Out-of-plane loaded masonry walls retrofitted with oriented strand boards: Numerical analysis and influencing parameters

The computational prediction of the out-of-plane behaviour of unreinforced masonry walls is a challenge. However, computational numerical models may provide, if properly calibrated, a powerful tool to predict the behaviour of new retrofit techniques. This paper presents the Finite Element (FE) modelling of masonry walls retrofitted with oriented strand boards (OSB) aiming the prediction of its out-of-plane behaviour. Such retrofit measure has been proposed by the authors for brick masonry walls and its efficiency has been demonstrated through experimental studies on small-scale and larger-scale masonry specimens (out-of-plane monotonic tests). The data gathered in the experimental phase has been used here to calibrate the numerical FE-based models (i.e. non-retrofitted and retrofitted). For this purpose, a detailed micro-modelling strategy has been followed assuming a perfect bond between mortar joints and brick units. The so-called Concrete Damage Plasticity (CDP) model has been adopted to describe the constitutive relation of the masonry and the OSB timber panel. The connection between the masonry and the OSB panel has been modelled through elastic anchors. Numerical results show a good agreement with the experimental data, in terms of observed damage pattern and capacity curve (within 10% difference). The calibrated numerical model has been instrumental in developing a parametric analysis to study the effect of different OSB thicknesses, the side of the application of retrofit, and the spacing between connections through anchor rods. These revealed that the out-of-plane capacity of the system is directly proportional to the OSB thickness and that the spacing between steel connectors should be lower than 500 mm for an adequate response.

Dynamic Evaluation of the Effects of Climate Change on the Energy Renovation of a School in a Mediterranean Climate

This paper addresses the effects of long-term climate change on retrofit actions on a school building located in a Mediterranean climate. Dynamic energy simulations were performed using Termolog EpiX 11, first with conventional climate data and then with future year climate data exported from the CCWorldWeatherGen computational software. To date, many incentive actions are promoted for school renovations, but are these measures effective in preventing the discomfort that will be found due to overheating generated by climate change? Today, one of the main objectives in retrofit measures is the achievement of ZEB (Zero Energy Building) performance. Achieving this target requires first and foremost a high-performance envelope. This study evaluates the impact of retrofit strategies mostly applied to the school building envelope, over the years, considering three different time horizons, until 2080. Thermal performance indices and indoor operative temperature under free-floating were evaluated. The results highlight that, with a changing climate, it is no longer possible to assume a constant static condition to evaluate retrofit actions, but it is necessary to develop a predictive mathematical model that considers the design variability for future years. There is an urgent necessity to ensure both the safety and comfort of buildings while also anticipating future variations in climate.

Coordinated energy-environmental-economic optimisation of building retrofits for optimal energy performance on a macro-scale: A life-cycle cost-based evaluation

Given that energy-efficiency policies focus on meso- or macro-scale interventions, it is imperative to establish a macro-scale evaluation approach for building retrofits to support policymaking in building energy conservation, management and sustainability. This study applies the generic idea of optimising the energy, economic and environmental outputs to propose a facile framework for evaluating the prospects of building retrofits on a macro-scale. Here, an extensive optimisation approach integratinglife cycle cost evaluation and an environmental assessment is formulated, involving coordinated on-site survey, modelling and data analytics. The model framework is corroborated by a case study analysis focused on identifying the optimal retrofit solution for low-rise office buildings in Shanghai. Simulation results show that modifications in occupancy regime, improvements in natural ventilation, heating and cooling systems, cool roofs insulation and installation of renewable energy systems (such as geothermal and solar/photovoltaics) are the basic retrofit measures for a macro-scale intervention to attain maximum life-cycle benefits. Individually, an estimated investment cost for each retrofit project varied within RMB 1 – 5 million with a payback period < 13 years, depending on the building characteristics. Overall, an investment estimated at RMB 1.7 billion (with a payback period of 6 years) is required to achieve ~ 80% energy reduction with a carbon dioxide savings of ~ 243 Gg-CO2/yr. In summary, this study provides a guidance framework for stakeholders to evaluate investments on retrofit projects, including existing and prospective ones.

Energy-efficient retrofitting of multi-storey residential buildings

Purpose Sustainable retrofitting of aged buildings plays a significant role in reducing energy demands and greenhouse gas emissions. This study aims to assess the performance and effectiveness of energy retrofit measures (ERMs) for an archetype of aged multi-storey residential buildings. Design/methodology/approach The methodology consists of three parts, namely, a desktop study including the selection of a case-study building and identification of ERM options for the building; development of a computer model to simulate the building’s energy use in the baseline scenario and different scenarios of ERMs; and evaluation of the ERMs based on energy-saving rate. Findings Among the 13 ERMs tested, lighting-related ERMs were found to be optimal measures while window fin is the least suitable option in terms of energy saving. Based on the research findings, a two-level retrofitting framework was developed for aged multi-storey buildings. Research limitations/implications Future studies may take a similar approach of this study to develop retrofitting frameworks for other types of buildings, and further research paper can be extended to study retrofitting for buildings in a district or a region. Practical implications The findings of this study can serve as a reference for building owners to select effective ERMs for aged multi-storey buildings, which invariably exist in developed cities. Originality/value This study presents a pioneering work where an energy model and a building archetype were used to analyze the energy savings of a variety of ERMs that are applicable to aged multi-storey buildings.

Retrofitting post-war office buildings: Interventions for energy efficiency, improved comfort, productivity and cost reduction

Within the UK non-domestic building stock, offices built between 1940 and 1980, are especially in need of retrofit, they can suffer from high energy consumption and thermal discomfort. Many post-war offices will still be in use throughout the first half of this century. This paper evaluates retrofit strategies for post-war office buildings accounting for the improved energy efficiency, thermal comfort and hence productivity, and reduction of capital and running costs. The aim of the paper is seeking optimal, generic retrofit strategies to provide guidance to building owners, occupiers and other decision makers. Dynamic thermal modelling is used to compare retrofit outcomes for existing building standards (PartL2B) and higher standards (Passivhaus retrofit: EnerPHit). The effects of location and orientation and both current and future UK weather conditions (2050) are considered. Multiple combinations of heating and cooling strategies and retrofit measures are assessed. The analysis methodology uses a sophisticated comfort, productivity and cost assessment. An Overall Building Thermal Discomfort (OBTD) index is introduced which enriches the current CIBSE overheating criterion 1 by including the number of occupants. Productivity improvements as a result of better comfort are included in cost calculations. Cost benefits are calculated both for buildings used by the owner (CBO) and for buildings let to a tenant (CBT). On cost and energy grounds, UK building regulation compliant retrofit is optimal provided that passive summertime overheating controls, such as night ventilation, blinds and/or overhangs, are installed. The EnerPHit standard retrofit provides resilience as the climate warms provided summer cooling is available, for example through mixed-mode ventilation.

Understanding low-carbon housing retrofit within a wider nexus of practices

Low-carbon retrofit of owner-occupied housing will make a significant contribution to reducing UK CO2 emissions. However, despite placing the home within its social context, there remain concerns that existing practice theory studies on this topic fail to adequately conceptualise ‘large’ phenomena such as retrofit. In response to this gap, this research adopts a novel nexus-of-practice approach to understanding home improvements. Drawing on thirty-one in-depth interviews and walk-through tours with owner-occupiers in Bristol, a rigorous line-by-line coding and analysis of the relationships between components of practice is undertaken. Particular attention is given to: connections between home improvement practices and the wider nexus of practices; how these connections can increase adoption of low-carbon retrofit measures; and the implications of these for the role of the architect. The findings reveal indirect relationships between low-carbon retrofit measures and other home improvement practices. They also illustrate that professional competences associated with low-carbon retrofit measures are poorly connected to the wider nexus. These connections have implications for policy seeking to encourage higher levels of low-carbon retrofit, and contribute to architects’ ability to recognise and seize opportunities to maximise the environmental benefits of owner-occupier home improvement projects.

Analysing Energy-Saving Behaviours in Italian Households

In the European context of moving to a low-carbon economy, knowledge regarding household decisions surrounding residential heating systems is crucial for policymakers in order to design effective policies both to reduce non-renewable energy consumption and to enhance energy efficiency in the residential sector. The choices made by households concerning decisions on how to heat their homes can significantly influence the related environmental impacts. This research examines two aspects of decision making with respect to heating system upgrades in Italian households using, for the first time, data from the 2013 Italian Households Energy Consumption survey: the choice of using renewable energies for space heating and decision to invest in energy efficient retrofits. Our findings show that household socio-economic characteristics and contextual factors are critical for good decision-making regarding heating system. We also find that previous cash retrofit investments and dwelling characteristics are important determining factors both for the choice of heating system based on renewable sources and for the subsequent decision regarding the adoption of energy efficient retrofit measures.

Method for probabilistic evaluation of post-earthquake functionality of building systems

Recent large earthquakes have caused significant building damage resulting in lengthy functional recovery times. Post-earthquake recovery time can be minimized through improved design of building systems essential for providing continuous operation. This study presents a novel method for probabilistic evaluation of the post-earthquake building’s functionality to support functionality-based seismic design. Aligned with the PBEE methodology, the proposed method utilizes FEMA P-58 damage assessment results in conjunction with fault trees of complex building systems to find the percent of building area with compromised functionality and to identify building components that impair its functionality. The primary user-defined inputs are probabilistic limit state functions of individual building components, which define the damage thresholds for partial (local) and full loss of the building functionality. The proposed method is highly flexible; it has a modular structure that allows easy extension by adding new features. A case study is conducted for an existing 13-story building to demonstrate the functionality evaluation and showcase how its results can guide the retrofit measures for improved seismic performance.

Evaluation of Rural Dwellings’ Energy-Saving Retrofit with Adaptive Thermal Comfort Theory

The purpose of energy-saving retrofit of rural dwellings is to obtain a more comfortable indoor thermal environment with reasonable investment. The utilization rate of heating and air conditioning equipment for dwellings in poor rural areas is very low, and the buildings operate in natural ventilation mode all year round. Since the existing research on energy-saving retrofit is aimed at air-conditioned buildings, the research methods and results are not applicable to rural dwellings. This paper proposes a set of energy-saving retrofit evaluation methods suitable for natural ventilation buildings and applies it to the research on energy-saving retrofit of rural dwellings in cold climate regions of China. The specific process is as follows: First, this paper analyzed the current situation using field research and established a typical building model. Second, the DesignBuilder software was used to simulate all 725 schemes. Subsequently, the three main retrofit measures (replacing the external insulation windows, setting the external wall insulation layer and setting the roof insulation layer) were analyzed separately, and the optimal parameters of each retrofit measure were obtained. Finally, the entropy weight method was used to perform a multi-objective optimization analysis on all retrofit plans. The results show that 6+12A+6-mm insulating glass windows + 50-mm external wall insulation + 90-mm roof insulation is the optimal energy-saving reconstruction scheme. Compared with the benchmark building, the energy-saving rate of the optimal scheme is increased by 23.81%, and the annual adaptive thermal discomfort degree-hours are decreased by 13.17%.

Retrofitting traditional buildings: a risk-management framework integrating energy and moisture

Traditional buildings constitute a large proportion of the building stock in many countries worldwide; around 40% of the UK’s housing stock was built before 1940 and was primarily made with solid masonry walls. Only 11% of UK solid-walled dwellings had insulation installed, suggesting the high potential of the low-carbon retrofit of traditional buildings. However, there is evidence of the occurrence of unintended consequences, often associated with excess moisture. A method is presented for moisture risk management that includes the development of a process and a framework. These tools are then integrated into a novel framework for the combined energy and moisture performance retrofit of traditional buildings. An example of the framework’s practical application is provided, with a focus on retrofit measures for solid-wall insulation. The proposed systematic approach demonstrates the interconnected nature of energy and moisture. It harmonises the principles needed to support organisations in the delivery of robust retrofit of traditional buildings through the integration of pre-retrofit building assessment and post-retrofit monitoring in the process. The risk-management process and framework presented can be valuable tools to support designers in providing robust and scalable retrofit measures and strategies. Practice relevance An integrated energy and moisture risk-management process is presented to support designers in the retrofit of traditional buildings. This is accompanied by a framework that explains the steps required for moisture risk management at the various stages of the retrofit process. This systematic approach harmonises the principles needed to support organisations in delivering robust low-carbon retrofits and integrates pre- and post-retrofit building assessment in the process. While previous work has addressed energy and moisture management separately, this integrates the two aspects into a framework for risk management. An example illustrates the relevant modes and methods of assessment and monitoring in support of risk management. When combined with practical guidelines and training, the risk-management process and framework can be valuable tools to provide robust and scalable retrofit measures and strategies. The framework was developed within the context of the UK construction industry; it can be adapted to other contexts.

Performance of passive retrofit measures for historic buildings that house artefacts viable for future conditions

Retrofitting a building normally aims to achieve a higher quality indoor climate in terms of thermal comfort or in terms of air quality, as well as reducing the building’s energy consumption. Alternatively, in buildings that house artefacts, the application of retrofit measures normally aims to improve the indoor climate in terms of the artefacts’ conservation. However, the outdoor climate, which greatly influences the indoor climate of buildings, is changing significantly. Hence, it is obvious that when retrofitting a building it is of key importance to consider this change, especially in historic buildings that house high-valued artefacts.This paper aims to study the performance of several types of retrofit measures in historic buildings that house artefacts by considering climate change. A validated hygrothermal model of a 13th-century church was used coupled with future weather files and a risk-assessment methodology based on damage functions.It was found that passive retrofit measures can mitigate some of the negative impacts that climate change is expected to induce in historic buildings that house artefacts. However, these measures can also lead to the decrease of the conservation metrics. Consequently, ranges of thicknesses of the analysed retrofit measures that ensure the conservation metrics are presented.

Why it’s so hard? Exploring social barriers for the deployment of thermal energy storage in Spanish buildings

Thermal energy storage (TES) has been a prominent topic of scientific and industrial research for the last decades as TES increases efficiency, reliability and economic feasibility of solar energy systems. Several TES technologies are today feasible and competitive from a scientific-technical, sustainable and economic point of view. However, the social awareness and acceptance of TES has not followed such a development, as socio-cultural and legal aspects to be considered for their broader implementation hinder it. The main objective of this paper is to analyse social and cultural barriers to TES adoption in the Spanish context. For this proposal, we use quantitative and qualitative data provided from professionals and experts of the building sector. Hereby the main ideas arising from the analysis: the economic crisis of 2008 and the poor condition of the existing building stock prevent the adoption of extensive retrofitting measures including energy efficiency solutions such as TES’ while TES is regarded as an emerging market in Mediterranean climates such as Spanish. The lack of expertise of professionals hinders the transmission of TES benefits to occupants. Besides, there is little dissemination of good practices and professionals are suspicious of the long term performance of such technologies.

Long-term savings persistence from existing building commissioning and retrofits

The persistence of energy savings due to the implementation of Existing-Building Commissioning (EBCx) is an important measure of the benefit of EBCx. This study analyzes the persistence of energy savings achieved from the implementation EBCx in nine buildings from 1997 to 2018. Each is served by a central utility plant (CUP) with metered chilled water (CHW) and heating hot water (HHW). EBCx was initially implemented in 1996/97. All buildings had follow-up ongoing commissioning or retrofit measures applied from 1997 to 2018. These and other building changes prevent accurate direct comparisons of 1997 EBCx savings with 2018 savings, but the overall 2018 savings are comparable to the 1997 savings due to the combination of ongoing commissioning measures and other energy efficiency measures implemented in the intervening years. This study examined the rate of savings degradation following each active intervention and the ability of exponential and linear decline expressions to model the savings degradation. Average degradation for HHW, CHW, and electricity savings was modeled equally well by exponential and linear decline expressions. HHW, CHW, and electricity showed predicted savings persistence of 59.3%, 80.6%, and 88.2%, respectively 10 years after the implementation of energy-saving projects if no follow-up were to be conducted.

Precast Concrete Building Construction and Envelope Thermal Behavior: A Case Study on Portuguese Public Social Housing

A considerable part of Southern European countries building stock was constructed before the implementation of national thermal regulations, and as such, it is currently exposed to challenges such as energy poverty and climate change. Portuguese public social housing presents a significant variety of construction systems and applied typologies. Among them, the “Novobra NK1”, a precast concrete construction system that exploits some innovative features in envelope components, has been used in several projects. Considering the importance of retrofitting to improve and adapt the thermal behaviors of buildings to face the aforementioned challenges, this article aims to provide an understanding of the behavior of a NK1 thermal envelope of a dwelling located in Covilhã, Portugal, and the impact of some constructive envelope retrofit measures applied. Results show that existing opaque envelope elements and glazed areas present characteristics that are no longer able to provide proper responses to contemporary building constructive requirements. External insulation was identified as a key retrofit measure, window replacement also being an advised solution for rigorous heating seasons. Improvements from the internal side of windows, such as roller shades, may provide few benefits during cooling seasons, and applying solar films is not advised without a proper thermal repercussion analysis.

A target-driven decision-making multi-layered approach for optimal building retrofits via agglomerative hierarchical clustering: A case study in China

The optimization of energy, environmental and economic (3E) outcomes is the principal approach to identifying retrofit solutions for a sustainable built environment. By applying this approach and defining a set energy performance target, this study proposes a makeshift decision framework that integrates a data mining procedure (agglomerative hierarchical clustering (AHC)) into the decision-making process to provide a simplified 3E assessment of building retrofits on a macro-scale. The framework comprises of three model layers: (1) a building stock aggregation model, (2) an individualistic 3E model that provides the sensitivity analysis for (3) a life cycle cost-environmental assessment model. The framework is demonstrated and validated with a case study aimed at achieving the set energy targets for low-rise office buildings (LOB) in Shanghai. The model defines 4 prototypical buildings for the existing LOB blocks, which are used for the individual evaluation of 12 commonly applied retrofit measures. Subsequently, a simplified LCC-environmental assessment was performed to evaluate the 3E prospects of 2048 possible retrofit combinations. The results uniquely identify retrofit solutions to attain the set energy performance targets and optimal building performance. Furthermore, the decision criteria for different investment scenarios are discussed. Overall, this study provides building investors an innovative framework for a facile and holistic assessment of a broader range of retrofit alternatives based on set performance targets.