Retrofit Strategies Research Articles

How occupant positioning systems can be applied to help historic residences manage energy consumption: A case study in China

Historic residences often suffer from low energy efficiency due to inadequate management and obsolete infrastructure. To ensure these buildings operate in an environmentally friendly manner, intelligent energy control and management are necessary. Accurate indoor user positioning is fundamental to realizing occupant-centric controls. However, historic dwellings, with architectural heritage preservation requirements and diverse operational modes, present multiple challenges in terms of occupant monitoring and energy management. This research proposes a BLE positioning system based on the SAE-CNN algorithm to realize the analysis and prediction of occupant locations in a cost-effective and minimally-intrusive manner. The process begins by dividing spaces based on the mapped BIM model and cluster analysis. The RSSI maps of wireless signals collected from the Bluetooth beacons in each space are then preprocessed by Gaussian filter and sliding window techniques. Lastly, a machine learning algorithm refines the prediction model, which is integrated into a digital twin platform designed for energy consumption management. The system was implemented in a traditional Chinese dwelling in Wufu town, Fujian Province. The results are promising, showing that the positioning accuracy reached 1.5–2 m (95 % confidence interval), while the platform effectively presented the real-time positioning results as well as realized occupant-centric energy management. Moreover, the collected location information shed light on occupants' spatial usage habits, offering valuable insights for devising decarbonization retrofit strategies.

Electrification of oil refineries through multi-objective multi-period graph-theoretical planning: A crude distillation unit case study

Electrification using renewable energy sources is the key to paving a sustainable and cleaner future for the oil and gas sector, which is known to be a significant carbon dioxide emitter. Nevertheless, the suitability of the electrification designs heavily depends on the seasonal availability of renewable energy sources. This work proposes to use a multi-period graph-theoretical (P-graph) approach to determine the optimal retrofit strategy to achieve electrification with consideration of economic and environmental factors. Both single-period and multi-period models are considered via a graph-theoretical approach to rank and evaluate all the combinatorically feasible electrification pathways based on the overall performance. The effectiveness of the proposed method is developed using a crude distillation unit (CDU) case study adopted from a multinational company. The effectiveness of the proposed method is illustrated using a crude distillation unit (CDU) case study shown in three different scenarios that include prioritizing economic aspect (Scenario 1), prioritizing environmental aspect (Scenario 2), and considering equal importance of both aspects (Scenario 3). For single-period operation, the results showed a mix of natural gas and hydropower energy, exclusive use of onshore wind energy, and a mix of onshore wind energy and biogas cogeneration energy for Scenario 1, Scenario 2, and Scenario 3, respectively. In contrast, the multi-period model also utilized nuclear energy for Scenario 2 and Scenario 3 given the seasonal availability constraint. Following that, a sensitivity analysis is conducted to see the effect of the absence of the most influential energy sources on the optimal solution of each scenario and the top solutions under budget and CO2 emission constraints. Pareto analysis is outlined to offer an understanding of tradeoffs between differently prioritized solutions that decision-makers can select. The combination of the proposed analysis provides a systemic approach towards transforming traditional industries towards a cleaner future via electrification.

Enhancing seismic performance of historic mosques through retrofitting measures

Historic mosques are structures that are highly sensitive to seismic events. Strengthening these buildings, which have been exposed to earthquakes throughout history, and ensuring their safe transfer to future generations is crucial. This research study focuses on three significant historic mosques in the eastern province of Türkiye, Erzurum. Their seismic performance, which has not been extensively studied in the existing literature, is investigated using finite element analysis. Dynamic analyses are conducted, utilizing seismic records from notable earthquakes that have caused significant damage to historic mosques in Türkiye, including the 1992 Erzincan, 1997 Düzce, and 2023 Kahramanmaraş earthquakes. As a result of dynamic analyses, the seismic vulnerability of the considered mosques has been determined. These vulnerable areas include the junctions of load-bearing walls, the dome ring, and the main dome. Based on these findings and considering recommendations from the literature, cost-effective and practical retrofit strategies are proposed to enhance the seismic performance of the mosques. The proposed strengthening aims to improve the interaction between load-bearing walls (diaphragm effect) and reduce displacements in the dome. Dynamic analyses are performed using the retrofitted models to assess the effectiveness of the proposed retrofit measures. These assessments were made considering displacements obtained from the dome and walls and the distribution of global damage. The results of 18 dynamic analyses confirm the efficacy of the suggested retrofit configurations in mosques featuring square plan layouts and single dome architectural styles.

Historic buildings to Positive Energy Buildings: a trilemma between energy efficiency, lifecycle carbon and architecture conservation.

Heritage buildings define the distinctive character of many urban areas by creating continuity with the past and serving as a visual cultural reference. To ensure their continued use, these buildings must be adapted for better performance that demands energy retrofitting strategies while satisfying indoor environmental quality. Energy retrofit reduces CO2eq emissions in the operation phase but typically entails embodied carbon and is not always applicable to historic buildings that require architectural and cultural conservation. This study phrases it as a trilemma and aims to identify an optimal balance between increased energy efficiency and decreased lifecycle carbon when architecture conservation is acknowledged. The research is applied to a traditional fisherman’s cottage in the village on Howth Head, Ireland with an aim to make it a Positive Energy Building (PEB). First, the construction method and heritage value are investigated followed by an experimental U-value calculation to identify the intervention needs. Then, a range of retrofit strategies to increase the energy efficiency of the building, but sensitive to the architectural conservation agenda, are proposed. Furthermore, using the EnergyPlus simulation engine, the study analyses the implications of different building materials for thermal insulation, building façade and window retrofit, on the building’s operational energy performance. Finally, for each scenario, a lifecycle carbon analysis was applied to identify the optimal strategy when architecture conservation is considered. The best retrofit strategies for reducing operational carbon do not always decrease embodied carbon. Similarly, the optimal materials to be used to achieve the highest level of energy efficiency and reduced life cycle carbon to become a PEB do not adhere to architectural conservation objectives. Further analysis is undertaken to achieve a balanced strategy which can be adopted in similar conservation retrofit projects.

Renovation of 20th century modern buildings: Some common challenging architectural details analysed to find optimal insulating solutions

Reusing existing buildings is a valid response to the architectural challenge associated with climate change. However, these buildings must be adapted for better performance to ensure low carbon impact in the future. That demands retrofitting strategies which enable thermal comfort, indoor environmental quality, and energy efficiency. In addition, energy retrofit solutions that abide by conservation ethos are needed to ensure higher performance while protecting cultural heritage, architectural features, and identity. Energy retrofits of post-war modern-age buildings pose particular challenges. There is a paucity of general guidance, particularly academic literature, focusing on optimum retrofit strategies for awkward architectural details. These optimum strategies mainly consider the balance between the retrofit cost and the energy-saving potential. Environmental concerns related to the insulation materials are often not mentioned. As the results of this study show, the “optimum” solution might shift once we add this third aspect. In certain instances, no or minimal insulation is often more optimal when considering the environmental effects associated with the insulation and additional materials involved in retrofits.

Airtightness of Estonian dwellings – median and base-values for heat loss estimation.

The field measurements of airtightness in Estonian detached houses and apartment buildings, conducted between 2003 – 2022, were combined into a large dataset for statistical analysis. The buildings (539 in total) constructed between 1810 and 2022 were classified based on dwelling type, building structure, number of storeys, year of construction, energy classification and compactness factors. The data was statistically analysed to determine the mean and median air leakage rates at 50 Pa and tested (Kruskal-Wallis test with post-hoc Conover test) for significant differences within the grouping factors. Buildings constructed after the enforcement of the compulsory Energy Performance certification have on average across all building structure types significantly lower mean air leakage rate (1.6 m3/(h·m2)) than older buildings (6.9 m3/(h·m2)), although log-wood and brick construction types feature slightly higher average air leakage rate. Previous experience with air leakage measurements help to achieve better airtightness on building site. A systematic and recurring measurement practice within a single construction company leads to significantly lower air leakage also for new concrete buildings. Detailed assessment of older buildings showed that all timber-based construction types had significantly higher air leakage rate along with higher variability compared to precast large concrete panel stone and small block wall and brick buildings. All apartment buildings built before 2010 had significantly lower air leakage rate compared to detached houses while there was no difference in new buildings. Along with the mean and median value a base value of air leakage rate q E50,base was calculated for all construction types and age groups including 50% of measured buildings around the mean within each group with 84 % confidence interval. The calculated mean, median and base values of air leakage rate provide a way for more accurate heat loss estimation at the district-level or building-level modelling of energy saving potential of different retrofitting strategies based on building age, construction type and other building information data.

Progressive collapse analysis and retrofit of a steel-RC building considering catenary effect

Despite their low probability of occurrence, the consequences of abnormal loads may be very important, both in economic terms and in terms of human lives. This has stimulated the development of strengthening and retrofitting techniques to mitigate the risk of progressive collapse of buildings. However, their application to real-scale buildings is still lacking. This paper describes the progressive collapse analysis and retrofit of a steel-reinforced concrete hospital building. The progressive collapse performance under different column removal scenarios is investigated using both nonlinear static and dynamic analyses. A two-step pushdown analysis procedure is developed to estimate the dynamic amplification factor (DIF) to partially compensate for the dynamic effects. The results have revealed the vulnerability of the building due to the low tensile axial resistance of the beam-to-column connections. Both the hypothesis of DIF = 2 and the almost inversely proportional relationship between DIF and vertical deflection have proven to be ineffective due to the catenary effect. A retrofit solution is proposed based on an outrigger-belt truss system on the rooftop level. The results show the effectiveness of the retrofit strategy. The displacement dynamic response of the retrofitted structure is significantly reduced if compared to the original structure since it goes from about 20 cm to less than 1 cm. However, the tensile strength of column-to-column connections of the top three floors is inadequate and should be increased. To this aim, a strengthening intervention is developed to increase the tensile strength from 565 kN to 965 kN, thus allowing the tensile axial forces caused by the column removed to be resisted.

Seismic Performance Evaluation and Retrofit Strategy of Overhead Gas-Insulated Transmission Lines

The overhead gas-insulated transmission line (GIL) in ultra-high-voltage converter stations, distinct from traditional buried pipelines, demands a thorough investigation into its seismic behavior due to limitations in existing codes. A refined finite element model is established, considering internal structure, slip between various parts, and the relative displacement at the internal conductor joint. Seismic analysis reveals the vulnerability of the GIL at the corner of the pipeline height change, with two failure modes: housing strength failure and internal conductor displacement exceeding the limit. Furthermore, the acceleration amplification coefficient of the support generally exceeds 2.0. Two retrofit methods, namely increasing the fundamental frequency of all supports and fixing the connections between all supports and the housing, have been proposed. The results indicate the effectiveness of both methods in reducing the relative displacement. Fixing all the supports effectively reduces the stress, whereas the other one yields the opposite effect. The seismic performance of a GIL is determined not by the dynamic amplification of supports, but by the control of relative displacement between critical sections, specifically influenced by the angular deformation of the pipeline’s first-order translational vibration mode along the line direction. Seismic vulnerability analysis reveals a reduction of over 50% in the failure probability of the GIL after the retrofit compared to before the retrofit, with the PGA exceeding 0.4 g.

Reviewing the contribution of retrofitting for climate resilience in residential buildings

Purpose Over the years, the significance of retrofitting has gained much attention with the unveiling of its different applications, such as energy retrofit and deep retrofit, to enhance the climate-resilience of buildings. However, no single study comprehensively assesses the climate-resilience of retrofitting. The purpose of this study is to address this gap via a systematic literature review. Design/methodology/approach Quality journal studies were selected using the PRISMA method and analysed manually and using scientometrics. Three dimensions of climate-resilience, such as robustness, withstanding and recovery, were used to evaluate the contribution of retrofit measures for achieving climate-resilient houses across four climate zones: tropical, arid, temperate and cold. Findings Most passive measures can enhance the robustness of residential buildings but cannot verify for withstanding against immediate shocks and timely recovery. However, some passive measures, such as night-time ventilation, show excellent performance over all four climate zones. Active measures such as heating, ventilation and air conditioning and mechanical ventilation with heat recovery, can ensure climate-resilience in all three dimensions in the short-term but contribute to greenhouse gas emissions, further exacerbating the long-term climate. Integrating renewable energy sources can defeat this issue. Thus, all three retrofit strategies should appropriately be adopted together to achieve climate-resilient houses. Research limitations/implications Since the research is limited to secondary data, retrofit measures recommended in this research should be further investigated before application. Originality/value This review contributes to the knowledge domain of retrofitting by assessing the contribution of different retrofit measures to climate-resilience.

The use of numerical models within the BIM environment, for the issue of Cultural heritage restoration. Buildings designed until 1940 in Albania

The study is related to the historical and architectural heritage of the city of Tirana, based on the period of Italian influence until 1940. The stock of these buildings represents an interesting case, in terms of research, since they are close to the 100th anniversary after the construction and have great values for the city, as well as architectural heritage. The lifespan of these objects depends on interventions over the years, conservation, updating with digital monitoring technology and the inclusion of BIM and h-BIM tools in the treatment process. It is important to mention that the building does not only need facade maintenance and refinishing, but by getting to know its fragile parts we can have a seismic retrofit strategy ready. Specifically, this research focuses on several digitization processes, 3D models, simulation and intervention proposals. One of the main aspects is the communication between computer models, dealing with the FEM numerical model and the architectural model inside and outside the BIM environment, reducing the gap between them and without major data loss. After analyzing the collapse scenarios, it is intended to increase the accuracy of seismic retrofit interventions, with the sensitivity that belongs to a cultural heritage object. The application of numerical models for legacy objects presents a challenge since the complexity of handling an old building, the parameters of materials, calibrations and approaching the real response of the building in a seismic situation is known. Applications through BIM tools and files with numerous numerical data tend to make a contribution to the field of seismic engineering and heritage restoration in Albania. Variants with proposals on seismic retrofit strategies for protected buildings will be given at the end of this study.

Multi-objective optimization of mitigation strategies for buildings subject to multiple hazards

Natural hazards can have a devastating impact on communities, leading to social and economic losses. These effects are particularly severe in multi-hazard contexts, where multiple disruptive events occur simultaneously or consecutively (such as earthquakes and tsunamis). To reduce the impact of such events, it is critical to enhance community resilience and make it more capable of withstanding and recovering from diverse types of damage. In this study, we propose a multi-objective optimization model to determine optimal retrofitting strategies to enhance community resilience under multiple hazards. We used the proposed model to analyze the impact of earthquake and tsunami hazards on the community of Seaside, Oregon. It assesses the effectiveness of different retrofitting strategies at the individual building level, considering the conflicting objectives of reducing overall economic loss, population dislocation, and building repair times. Our results demonstrate that retrofitting buildings to achieve higher seismic codes can significantly reduce the impact of natural hazards on structural damage, population dislocation, and building repair times. Additionally, our findings reveal the importance of considering geographical location and mitigation measures when optimizing retrofitting strategies. By considering budget constraints and community resilience metrics, our model identifies the most effective retrofitting strategies for individual buildings of Seaside, which ultimately helps the community make informed decisions about investments to reduce the impact of natural hazards. Overall, this study provides valuable insights into the importance of enhancing community resilience in multi-hazard contexts and showcases the use of a multi-objective optimization model to identify optimal retrofitting strategies.

Optimal building retrofit pathways considering residential energy use variability: A case study of Nanjing city

The variation in energy usage patterns among occupants elucidates the disparity between projected and realized energy consumption following physical retrofitting, and serves as a significant determinant in the context of extensive building retrofit initiatives. This study involves the establishment of four representative building models in regions characterized by hot summers and cold winters. The study examines the diverse energy consumption patterns exhibited by occupants, and subsequently explores the potential strategies for implementing large-scale energy-efficient renovations in the hot summer and cold winter zones. The findings indicate that there is a prevalent occurrence of excessive energy consumption. Moreover, the energy usage patterns exhibited by occupants have a substantial influence on the overall energy consumption of buildings. The implementation of graded and progressive stepped-step electricity pricing should be prioritized during both summer and winter seasons. This entails appropriately increasing the price of stepped-step power tariffs and reducing the proportion of residents who consume excessive energy. Undoubtedly, the most successful large-scale retrofit scheme for hot summer and cold winter areas is the replacement of all air conditioning equipment in the existing residential areas, under the premise of adopting the seasonal progressive incremental ladder energy pricing.

National building stock model for evaluating the impact of different retrofit measures

In this study, a methodology was developed to evaluate different retrofit strategies, which allows an estimation of the current and future thermal space heating demand of the approximately 1.8 million residential buildings in Switzerland. The approach is based on a building stock dynamics model that considers new buildings, replacement buildings, demolitions, as well as past and current rates of energy-related retrofits. Different potential retrofit strategies are applied to evaluate their impact on reducing space heating demand. The results show the effectiveness of the distinct retrofit strategies in reaching the target reduction and emphasize the differences in the resulting annual retrofit rates. The simulated specific retrofit rates can serve as a basis for developing building retrofit measures at the national level, as well as for informing the next generation of regulations.

Assessment of operational and embodied energy in passive residential retrofitting strategies for the Mediterranean climate

This study contributes to the research of lifecycle environmental impact in buildings’ passive strategies, specifically passive strategies incorporated during the energy retrofitting of residential buildings in the Mediterranean climate. With a simplified lifecycle methodology, this research considers operational and embodied energy and CO2 emissions calculations to compare the results of the two passive strategies and the existing dwelling. In a 50-year reference period, results show that the operational improvement gained with the passive strategy can be reduced or cancelled due to the consideration of the embodied energy and CO2 emissions attributed to the additional materials.

Future indoor overheating risk for urban village housing in subtropical region of China under long-term changing climate

Over the last two decades, China has witnessed a surge in the emergence of urban villages characterized by high building density and significant migrant populations, primarily due to shifts in land use during urbanization. Housings in urban villages with low-cost design strategies, potentially exposing them to indoor overheating risks under climate changes. Given the scarcity of literature analyzing thermal performance of these houses, this study aims to assess the future indoor overheating risk of common urban village house types based on different construction material in subtropical China with two metrics which are Indoor Overheating Hours (IOH) and Indoor Overheating Degree (IOD), and explore effective methods to counter outdoor thermal stress. A four-month on-site measurement was conducted to calibrate the building thermal environment calculation model. Results demonstrate pronounced indoor overheating risks for both selected houses, Traditional Urban Village House (TUVH) and Contemporary Urban Village House (CUVH), particularly under the Representative Concentration Pathways (RCPs) 8.5 scenario. TUVH and CUVH may experience up to 2111 and 4325 overheating hours, respectively, with the IOD reaching 7.1 °C and 10.9 °C. Moreover, employing a global sensitivity analysis, we found that adding opaque shading for external wall is an effective retrofit strategy for TUVH and CUVH. This study contributes to evaluating the thermal performance of urban village houses under long-term climate changes with the findings promoting future retrofit strategy research for urban village houses focusing on housing types and usage pattern of the housings.

Evaluating carbon emissions from the operation of historic dwellings in cities based on an intelligent management platform

Historic dwellings in cities are considered to be an important resource on the way to carbon neutrality because of their great potential for low-carbon renewal. However, in addition to obligatory heritage conservation requirements, there is no uniformity in historic dwellings’ operation mode and conditioning equipment, which means detailed carbon emissions accounting is critical but challenging. To estimate the spatio-temporal distribution of carbon emissions from historic dwellings and thus support the development of decarbonization retrofit strategies, this research proposed a low-interventional carbon footprint accounting system based on a digital twin management platform. Multiple digital technologies are applied to monitor and evaluate the occupants’ lifestyles, indoor environment, user location, and equipment energy consumption. Based on backend algorithms, the spatio-temporal distribution of carbon emissions is inserted into the building plan to graphically present the evaluation results. Compared with traditional simulation methods, the proposed system enables the automatic updating of energy accounting parameters by fusing multi-source data into one platform, improving accounting efficiency and accuracy simultaneously. A case study in China proves the outstanding performance of the accuracy of accounting results, with an approximate daily spatial error of 20 % and a total accounting error of less than 15 %.

NUMERICAL MODELLING OF REINFORCED CONCRETE FRAMES RETROFITTED WITH BUCKLING RESTRAINED BRACE INCORPORATING STEEL AND SUPERELASTIC SHAPE-MEMORY ALLOY CORES

The numerical response of one-storey reinforced concrete frames designed following design standards before the enactment of modern seismic provisions was investigated in this study using the nonlinear finite element method. An unbraced frame and two frames retrofitted with a buckling restrained brace (BRB) incorporating either a stainless steel or chrome molybdenum core bar were modelled. The nonlinear static reverse cyclic loading performance of the frames was assessed. Modifications to the BRB are proposed to mitigate deficiencies identified with the original BRB and steel core bars. The modified BRB incorporating a superelastic shape-memory alloy (SE-SMA) core bar was further modelled. The results illustrate the benefits of implementing SE-SMA as a retrofit strategy to control permanent displacements. The modified BRB with a SE-SMA core exhibited improved lateral strength and displacement capacities relative to the frames retrofitted with steel cores and the control bare frame.

Optimizing automated shading systems for enhanced energy performance in cold climate zones: Strategies, savings, and comfort

Enhancing urban sustainability requires innovative strategies to improve energy performance while maintaining occupant comfort in new and existing buildings. Buildings located in cold climate zones with high glazing-to-wall ratios often face unwanted solar gain and heat loss that, in turn, negatively impact building energy performance. Though automated shading systems effectively reduce excessive indoor solar gain in warm climates, a research gap exists regarding their ability to enhance building energy performance in heating-dominant climates. This paper investigates automated shading implementation for cold climate zones and develops a novel cold climate optimized sensorless control strategy for interior roller shades. A field study was conducted to assess the impact of roller shade operation on indoor thermal conditions. Results from the field study showed that the prototype roller shades operating on the developed control strategy reduced daytime indoor peak temperatures during the summer season to 26.4 °C ± 0.5 °C from 30.0 °C ± 1.9 °C and 28.5 °C ± 1.2 °C for the unshaded and shaded static operation baseline scenarios, respectively. During winter season tests, shade deployment reduced the overnight indoor cooling rate from 0.60 °C/hr ± 0.30 °C/hr and 0.42 °C/hr ± 0.18 °C/hr. A mathematical model was also developed to estimate shading system energy performance based on user-defined building specifications and weather-related variables. It was found that automated shading systems are suitable for use as a green retrofit strategy for cold climate zone buildings. The technology exhibited a payback period range of approximately 5–15 years, depending on factors such as glazing type, glazing orientation, solar exposure, and local climate conditions. Findings from both the simulation and prototype field study support the use of cold climate-optimized automated shading systems to improve overall building energy performance - reducing both building heating and cooling-related energy consumption.

Reliability Estimation of the Compressive Concrete Strength Based on Non-Destructive Tests

The uncertainty in the concrete compressive strength is one of the most challenging issues in safety checking of existing reinforced concrete (RC) buildings. The concrete compressive strength used in the assessment can highly influence the vulnerability results and thus the retrofit strategies. The need to use less expensive and less invasive in situ measurements such as the non-destructive tests should be balanced with a careful check of their structural reliability. The compressive concrete strength is characterized herein based on a large database of both in situ destructive and non-destructive results measured on the same structural members. The data are obtained from existing RC buildings mainly located in the Campania region, Southern Italy. Probabilistic linear and multilinear regression models are developed for calculating the compressive concrete strength based on non-destructive tests. Furthermore, the implementation of the concrete strength based on ultrasonic test results are investigated together with the relative measurement error through a fully probabilistic workflow. Accordingly, the relative weights of non-destructive data for calculating concrete compressive strength are estimated and compared with those recommended by the Italian national code. The results demonstrate that the effective weights of the non-destructive data are very close to the code-based recommendation.

Investigation of Greening Façade and Retrofitting strategies on Outdoor Thermal Comfort and Indoor Energy Consumption in New Assiut City, Egypt

Investigation of Greening Façade and Retrofitting strategies on Outdoor Thermal Comfort and Indoor Energy Consumption in New Assiut City, Egypt