Retrofit Costs Research Articles

Joint optimization of building-envelope and heating-system retrofits at territory scale to enhance decision-aiding

Reduction of energy consumption in the building sector has been identified as a major instrument to tackle global climate change and improve sustainability. In this paper, we propose a methodology to address a retrofit planning problem at a community level, with a building resolution. The resulting tool helps local decision-makers identify pertinent actions to improve the environmental behavior of their territories. Two building retrofit levers are considered, namely envelope insulation and heating systems replacement. Retrofit planning is treated here as a single-objective optimization problem aimed at reducing the total costs of retrofit actions by minimizing their net present value. A multidimensional multiple-choice knapsack problem formulation is proposed through the adoption of adequate decision variables. It suitably balances the complexity induced by the large number of potential retrofit action combinations and the number of variables in the problem and permits a linear formulation. An optimization of virtual building stocks is performed to highlight the developed model’s capacity to tackle large problems (5,000 buildings) in a few minutes. Finally, three analyses finally are led on a real case-study territory, featuring both appropriate retrofit solutions and building stock information. Long-term evaluation of retrofit strategies over the short-term results in an additional 10% reduction of energy consumption and greenhouse gases emissions and encourages thermal insulation. When targeting a 40% reduction in energy demand, retrofit costs ranging from 20 to 800€/m2 are observed. Finally, the developed method was used to draw a CO2 abatement cost curve at territory level. A 70% reduction of emissions can be achieved with costs under 50 €/tCO2e.

A predictive modeling approach to estimating seismic retrofit costs

This paper presents a methodology for estimating seismic retrofit costs from historical data. In particular, historical retrofit cost data from FEMA 156 is used to build a generalized linear model (GLM) to predict retrofit costs as a function of building characteristics. While not as accurate as an engineering professional's estimate, this methodology is easy to apply to generate quick estimates and is especially useful for decision makers with large building portfolios. Moreover, the predictive modeling approach provides a measure of uncertainty in terms of prediction error. The paper uses prediction error to compare different modeling choices, including the choice of distribution for costs. Finally, the proposed retrofit cost model is implemented to estimate the cost to retrofit a portfolio of federal buildings. The application illustrates how the choice of distribution affects cost estimates.

Bottom-up building stock retrofit based on levelized cost of saved energy

Policy makers need scientific support to set ambitious yet realistic environmental targets for the transition to energy efficient buildings and to develop cost-effective policies to meet these targets, but comprehensive, manageable procedures to this aim are still lacking. Our proposed method ranges from baseline creation to transition scenarios depending on annual retrofit budget and specifies the buildings to renovate according to location, size, and age, and the energy efficiency measures to apply based on cost and energy saving. We show how to extrapolate a baseline from few available data, determine retrofit costs, and create calibrated models to estimate energy savings. Retrofits are ranked by levelized cost of saved energy, which ensures that for any budget allocated to retrofit maximum energy savings are obtained at minimum cost to society. The results are summarized in an energy efficiency cost curve enabling policy makers to estimate potential costs and energy savings. We demonstrate the method on a housing stock in northern Italy and show that facade insulation of old buildings in colder climates can compete with gas heating. About 60% baseline energy consumption can be saved doubling current investments, while a maximum saving of 75% requires over three times the current investments.

Damage‐Based Seismic Retrofitting Approach for Nonductile Reinforced Concrete Structures Using FRP Composite Wraps

Applying similar amount of fibre reinforced polymer (FRP) for all plastic hinge locations in a structure is not an ideal approach as damage occurring at these critical locations may vary considerably. Building owners also always want to keep FRP retrofitting cost and associated interruption to a minimum. In this context, the current paper proposes an FRP retrofitting approach, in which FRP is selectively distributed based on the distribution of seismic damage in structures. The proposed approach, characterized by both quantitative and qualitative criteria, is simple but very effective in simultaneously reducing the seismic damage, amount of FRP to be used, and time of installation. For the considered cases of low‐ and mid‐rise nonductile building structures, the FRP amount reduced approximately by 31% compared to the cases in which FRP was evenly distributed, leading to lower installation cost and less interruption time. Interestingly, although 31% FRP was saved, the damage indices of the FRP retrofitted frames were significantly lower than those in cases of even FRP distribution because FRP effectively served for critical locations. Due to its simplicity and technical/economical effectiveness, the proposed FRP retrofitting approach can be useful for engineering practice.

A bi-objective optimization approach for selection of passive energy alternatives in retrofit projects under cost uncertainty

Abstract Improving energy performance of buildings is of particular importance in new construction and existing buildings. Building refurbishment is considered a practical pathway towards energy efficiency as the replacement of older buildings is at a slow pace. There are various ways of incorporating energy conservation measures in buildings through refurbishment projects. As such, we have to choose among various passive or active measures. In this study, we develop an integrated assessment model to direct energy management decisions in retrofit projects. Our focus will be on alternative passive measures that can be included in refurbishment projects to reduce overall energy consumption in buildings. We identify the relative priority of these alternatives with respect to their non-monetary (qualitative) benefits and issues using an analytic network process. Then, the above priorities will form a utility function that will be optimized along with the energy demand and retrofit costs using a multi-objective optimization model. We also explore various approaches to formulate the uncertainties that may arise in cost estimations and incorporate them into the optimization model. The applicability and authenticity of the proposed model is demonstrated through an illustrative case study application. The results reveal that the choice of the optimization approach for a retrofit project shall be done with respect to the extent of variations (uncertainties) in expected utilities (benefits) and costs for the alternative passive technologies.

The Impact of Grants on Homeowner Decisions to Retrofit to Reduce Hurricane-Induced Wind and Flood Damage

AbstractAn increasing number of national, state, and local programs have offered grants or other monetary incentives to encourage homeowners to retrofit their homes to reduce damage from natural hazard events. Despite this fact, little is known about how these offerings influence a homeowner’s decision to carry out such structural retrofits. This paper studies the impact that different grant program designs in particular have on the decision to undertake different types of retrofits to mitigate against hurricane damage. Using data from a survey of homeowners in the eastern half of North Carolina, we implement a mixed logit model that allows for the combination of both revealed-preference and stated-preference data available from the survey. Our findings show that offering a grant results in households being, on average, 3 times as likely to retrofit as when a grant is not offered. In addition, both the percentage of retrofit cost and the maximum dollar amount covered by the grant have a substantial impact on the probability that households choose to retrofit. Living closer to the coastline also has a significant impact on the probability that households will choose to retrofit. Counter to some previous research, we find that households who have experienced two or more hurricanes are less likely to choose to retrofit their homes. From our research, we find that the percentage of retrofit cost covered by the grant and the total cost are both important factors when deciding on the best grant program configuration.

A Survey on Coping With Intentional Interference in Satellite Navigation for Manned and Unmanned Aircraft

Intentional interference in satellite navigation is becoming an increasing threat for modern systems relying on Global Navigation Satellite Systems (GNSS). In particular, critical applications such as aviation can be severely affected by un-detected and un-mitigated interference and therefore interference management solutions are crucial to be employed. Methods to cope with such intentional interference enclose interference detection, interference mitigation, interference classification, and interference localization. This paper offers a comprehensive survey of interference management methods developed in the last four decades by the research community. After reviewing the main concepts of GNSS-based navigation, the interference and interference management solutions are classified, with a particular focus on the two major threats in GNSS navigation, namely jamming and spoofing. Mathematical models, comparative tables for various interference management solutions, such as detection, localization, mitigation, and classification, as well as comparative numerical results based on several selected algorithms are also presented. We especially focus on algorithms relying on omni-directional antennas, which do not require additional specific antennas to be installed on the aircraft and thus reduce the costs of retrofit and installation. 1

Crowdsourcing Model for Energy Efficiency Retrofit and Mixed-Integer Equilibrium Analysis

Most existing models of energy efficiency retrofit are able to evaluate energy saving and retrofit cost for a certain stakeholder, but unable to guide how to allocate retrofit task and incentive among multiple stakeholders. The multistakeholder situation is firstly modeled in the proposed crowdsourcing model (CM), which contributes to quantify the utility of each competitive stakeholder with respect to participation decision. To solve the CM, a Stackelberg game approach is newly developed in this article to find rational and efficient strategies of task/incentive allocation. For the building energy efficiency retrofit, the challenge of CM is to handle mixed-integer decisions of energy service companies. We prove the existence of Stackelberg equilibrium (SE), which introduces the optimal budget, and the Nash equilibrium of task allocation. To compute the SE of CM, effective search algorithms are designed based on best response and optimization techniques. Simulation results have verified the CM and game theoretical approach. The resulted SE has provided stable and efficient strategies of incentive/task allocation.

Retrofitting strata property - a tool supporting long-term retrofit strategy

Strata property - ownership of apartments or townhouses consisting of private and commonly owned building components and areas - was established in Switzerland in 1965 and since has become very popular. But, well-needed retrofit work of these buildings is often postponed and long-term retrofit strategies are rarely considered. However, the low retrofit rate must increase to meet the global energy goals. Interviews and workshops with relevant actors showed that missing financial means are not the key issues for the low retrofit rate. Major challenges arise from a broad set of issues, such as difficult processes, unclear responsibility, insufficient communication, missing building information or underestimation of the commonly owned building components. “Luzerner Toolbox” provides eight folders that address the key clusters of challenges. Central to this toolbox are Excel-based tools, which transform accurate technical and financial information into a visual format. An ample diagram illustrates the remaining lifetime of the building parts and a graph relates upcoming retrofit costs and the annual payments into the contingency reserve fund with a forecast of the contingency reserve fund. As such, these tools assists in scheduling appropriate retrofit measures and establishing a balanced financial planning. But, various actors have reported that the retrofit timetable is too complex to be used in management firms. Feasibility studies and further research of their specific needs and work processes are needed to refine the tool accordingly. In a further study, interviews with management firms and architects are conducted to determine the key factors of a useful tool.

Pre-Disaster Retrofit Decisions for Sustainable Transportation Systems in Urban Areas

A transportation system is an important material base for implementing timely rescue and emergency evacuation after disasters in urban areas. In order to reduce disaster risks and develop sustainable transportation systems, it is important to improve their resilience and ensure their reliability. This paper mainly studies pre-disaster retrofit decisions for sustainable transportation systems in urban areas. As the optimization goal, pre-disaster retrofit costs and post-disaster restoration costs under constraints of post-disaster system connectivity, travel time reliability, and post-disaster link capacity are taken into account to construct a bi-level stochastic programming model. A method based on the simulated annealing algorithm and Frank–Wolfe algorithm is used to solve the problem. The case study shows that the calculation is quick, and the result is reasonable. The study result proves that the method proposed in this paper can provide an effective solution to such problems.

Energy and Economics Analyses of Condenser Evaporative Precooling for Various Climates, Buildings and Refrigerants

Condenser evaporative pre-coolers provide a low cost retrofit option for existing packaged rooftop air conditioning application units. This paper aimed to provide a comprehensive study to assess energy savings and peak power reductions of condenser evaporative cooling. Condenser evaporative cooling leads to a lower temperature of the air entering the condenser of a rooftop unit, which results in smaller compressor power consumption. Using EnergyPlus building energy simulations, we mapped the impacts on energy savings and energy reductions at peak ambient temperatures in three building types and 16 locations with levels of pad effectiveness and demonstrated the effects on air conditioner using either R22 or R410A as refrigerants. Economics and control strategy to maximize the cost saving were also investigated. The results demonstrate that energy savings are much greater for HVAC systems with the refrigerant R410A than they are with R22, and evaporative pre-cooling provides the opportunity for annual energy savings and peak demand reductions, with significant potential in hot, dry climates. Additionally, we validated an improved mathematical model for estimating the condenser pre-cooling wet bulb efficiency which shows clear advantage over the current EnergyPlus model.

Application of artificial neural network and geographic information system to evaluate retrofit potential in public school buildings

School buildings in Italy are outdated, in critical maintenance conditions and they often perform below acceptable service levels and quality standards. Nevertheless, data supporting renovation policies are missing or very expensive to be obtained. The paper presents a method for evaluating building's energy savings potential, using the Building Energy Certification (Certificazione Energetica degli Edifici - CENED) open database. The aim of the research concerns the development of a data-driven set of methods, based on the use of open data, machine learning (ML) and Geographic Information Systems (GIS) to support regional energy retrofit policies on school buildings. The main advantage concerns the possibility to predict the post-retrofit energy savings, avoiding the expensive on-site Condition Assessment (CA) phase. Data have been first clustered to identify the most common thermo-physical properties of the envelope, then three retrofit scenarios have been defined, to allow the retrofit of homogeneous types of buildings. The energy saving potentials have been evaluated through the implementation of eight Artificial Neural Networks. Ultimately, data have been geolocated and further processed to support the definition of the energy retrofit policies for the most critical regional areas. The Lombardy region has been chosen as case study to test the robustness of the proposed methods. The results of the case study proved that school buildings energy retrofit policies can be supported and defined using available open data, ML and GIS. The future developments of the research concern the further integration of GIS for retrofit cost assessment and scenario analysis.

A Hybrid Multi-Objective Optimization Framework for Preliminary Process Design Based on Health, Safety and Environmental Impact

Due to increasingly stringent legal requirements and escalating environmental control costs, chemical industries have paid close attention to sustainable development without compromising their economic performance. Thus, chemical industries are in need of systematic tools to conduct sustainability assessments of their process/plant design. In order to avoid making costly retrofits at later stages, assessments during the preliminary design stage should be performed. In this paper, a systematic framework is presented for chemical processes at the preliminary design stage. Gross profit, Health Quotient Index (HQI), Inherent Safety Index (ISI) and the Waste Reduction (WAR) algorithm are used to assess the economic performance, health, safety and environmental impact of the process, respectively. The fuzzy optimization approach is used to analyse the trade-off among the four aspects simultaneously, as they often conflict with each other. Deviation between the solution obtained from mathematical optimization model and process simulator is determined to ensure the validity of the model. To demonstrate the proposed framework, a case study on 1, 4-butanediol production is presented.

An Integrated Disaster Preparedness Model for Retrofitting and Relief Item Transportation

Abstract In this study, a two-stage stochastic integer programming model is developed with a centralized planning perspective to simultaneously address mitigation and response decisions in humanitarian logistics, where the mitigation decisions involve both building and transportation infrastructure retrofitting. The objective is to minimize the total cost of retrofitting, relief item transportation and relief item shortage under a limited mitigation budget. Due to the excessive number of binary decision variables, solving the model becomes computationally difficult. Therefore, we propose Lagrangean relaxation to decouple the overall model and solve it by Lagrangean heuristics. Computational results indicate the efficiency of the solution approaches in providing high quality feasible solutions to problem instances of realistic size and complexity.

Investment decision-making optimization of energy efficiency retrofit measures in multiple buildings under financing budgetary restraint

Regarding to energy efficiency retrofit investment to numerous buildings, which buildings should be invested and which of the retrofit measures should be implemented for investable buildings are challenging tasks. The current literature have studied on choosing energy efficiency retrofit measures in single building, relatively little attention has been paid to the retrofit investment decision-making in multiple buildings. In addition, the existing studies almost put the retrofit cost as an objective that need to be minimized, and the retrofit capital budget is not taken into consideration. This paper proposes a decision-making optimization framework for energy efficiency retrofit investment in numerous buildings under financing budgetary restraint. A multi-objective optimization model with the economic goals being the net present value and time of return, and the environmental goals being the energy saving and emission reduction is presented, and then the intelligent optimization method combing particle swarm optimization and genetic algorithm is designed to search the retrofit investment strategy. The obtained investment strategy could determine which of the buildings should be invested to retrofit, and the combination of retrofitting measures for every investable building. An empirical study is conducted on 27 buildings of non-governmental organization in the state of Delaware in the United States, and the results indicate that the validity of the proposed framework. The findings indicate that the framework is an effective approach to assist the sustainability goal at regional level.

Application of a Comprehensive Seismic Retrofit Procedure for Steel Buildings Using Nonlinear Viscous Dampers

This study presents application of a new methodology to determine the characteristics of nonlinear viscous dampers (NLVDs). It also determines the optimum retrofitting level (ORL), by providing a novel and straightforward formulation without complex calculations. Inter-story drift ratio is considered as the effective parameter to calculate the failure cost of structures and to define limit states. To determine the ORL in low, medium and high-rise steel structures, three benchmark structures with different dynamic characteristics are studied. In addition, to validate the results in different zones with various seismic hazard levels, earthquake records representing three earthquake hazard levels are used in time history analysis. Based on the numerical results from nonlinear time history analyses, this comprehensive design procedure can be efficiently used to make seismic design of steel buildings with NLVDs, thereby meeting structural performance targets for any earthquake record at any intensity. Notably, use of the comprehensive design procedure reduces inter-story drift ratio to less than 0.7 in most building stories, suggesting that the building remains in immediate occupancy state under the applied earthquake records. Further, it can efficiently reduce the life-cycle costs and establish balance between the retrofit costs and failure reduction costs once structural retrofitting is performed.

Energy and environmental payback times for an NZEB retrofit

As of 2021 all new buildings within the European Union will be nearly Zero Energy Buildings (NZEB). Different plans are being promoted by member states to reach this goal, to increase the number of NZEBs and to facilitate the retrofit of existing constructions. Within this frame, several analyses of cost benefits have been developed to evaluate the economic effectiveness of retrofit interventions. The economic analysis can be extended to the energy and environmental fields introducing various indicators, such as energy and environmental payback times, to describe the effectiveness of the retrofit intervention from a more extensive point of view.In this paper, we considered a school building located in Turin (Northern Italy) with the scope of evaluating the energy and carbon payback times of different retrofit scenarios that could be implemented for the existing building. An optimal cost retrofit and two NZEB retrofits were considered, varying envelope insulation, heat generation and lighting systems, shading and control devices. First, we simulated the building's energy consumption and calibrated the results with data from actual energy bills. The calibrated model was used for evaluation of the building's energy demand after the proposed retrofit interventions. We then applied the Life-Cycle-Analysis (LCA) for the calculation of environmental payback times. The results showed that the NZEB retrofit produces energy and environmental payback times that are shorter than the life cycle of the building. In the foreseeable future, solutions such as these could prove effective in addressing issues that arise from global warming and energy supply.

Rollover Protective Structures, Worker Safety, and Cost-Effectiveness: New York, 2011-2017.

To measure cost-effectiveness of an intervention to increase retrofitting of rollover protective structures (ROPS) on tractors. Tractor overturns are the leading cause of farm fatalities. ROPS prevent these deaths. This study updates a 2011 cost-effectiveness assessment of a New York State intervention to increase use of ROPS. We subtracted intervention cost from the cost of injuries averted, then divided this figure by the number of averted injuries. We used related probabilities and costs of fatalities and injuries from published literature to calculate the program's cost-effectiveness. The total cost of the injuries averted from 2007 to 2017 was $6 018 742 versus a total program cost of $1 776 608. The one-time retrofit costs will continue to prevent injuries as long as the tractors are used, generating additional (projected) future savings of $12 136 512, $15 781 027, and $18 924 818 if retrofitted tractors remain in operation 15, 20, or 25 years after their retrofit. Social marketing was cost-effective for reducing injuries from tractor overturns. Public Health Implications. These results indicate that the intervention model is effective from both a public health and economic standpoint and should be expanded into other states.

Multidisciplinary Tool for Evaluating Strengthening Designs for Earthquake-Prone Buildings

In many seismically active countries, there is a high level of earthquake risk because of the presence of large stocks of earthquake-prone buildings. The typically high cost of earthquake retrofit and the difficulties associated with satisfying the interests of multiple stakeholders within a meaningful time frame potentially result in building demolition as the default seismic risk reduction solution. The Heritage Evaluation Framework (HEF) is a multidisciplinary decision-making tool to guide proposed seismic retrofit design by gathering inputs from all project stakeholders and to evaluate a particular seismic retrofit design against client expectations. The performance of the HEF is demonstrated for two retrofit projects using input data acquired via interviews, site walkthroughs, and regular meetings with project teams and clients. Results show that the HEF accommodates conceptual designs and provides useful feedback while encouraging early multidisciplinary collaboration.

Energy Efficiency Retrofit of Two-Flow Heat Exchanger System

This paper presents the retrofit of the two-flow heat-exchange system with utility paths in order to optimize the heat recuperation capacity under the technical limitation conditions. Analytical dependences of heat load of the existing heat exchangers and utilities on the surface area of the new heat exchanger are obtained. The work shows that the determination of technological parameters for existing heat exchangers during the retrofit of the heat exchange system is an important task because they affect the cost of retrofit. For case study, two streams problem for heat transfer in heat network at the crude and gas separation units is considered in this paper. The existing system has three heat exchangers. The temperature measurements were fulfilled for all heat exchangers and the heat loads for heat exchangers and utility were calculated. The installation of one heat exchanger at the cool side of the system is proposed in retrofit. The dependences of the temperature changes for the hot and cold process stream from the value of the additional surface were obtained for each heat exchanger. Utility capacity and capacity recovery of thermal energy in the system is also analyzed.