Building Energy Retrofit Research Articles

Energy retrofitting of heritage buildings: an integrated methodology

A resilient and sustainable way of life presupposes the reduction of the energy consumption and the relevant greenhouse gas (carbon) emissions. This approach leads to the establishment and implementation of various directives and regulations regarding the refurbishment of the existing building stock. Often, these regulations exclude heritage buildings due to the lack of robust methodologies which will ensure a balance between the energy retrofitting and preservation of the building’s heritage values. Heritage buildings however, host a variety of public uses and their holistic and successful energy upgrade could serve as an excellent example of a heritage building energy refurbishment to the community. Thus, there is an emerging need for developing such methodologies. This paper aims to propose an integrated methodology for the energy retrofitting of heritage buildings, based on a multi-criteria decision-making process for the selection of the appropriate retrofitting solutions considering simultaneously the heritage significance, the heritage and the energy impact.

Assessment of the Incentive Rate to Favor the Energy Retrofit of Public Buildings: A Comprehensive Approach for an Italian University Facility

The Renovation Wave for Europe highlighted the role of the public building stock for which Directive 2012/27/EU has set an annual renewal rate of 3%, which should rise to reach the goal of decarbonization by 2050. In this paper, the energy retrofit of an educational building—at the academic level—in Southern Italy was investigated. The aim was to evaluate the incentive share, which could accelerate the energy efficiency process, to achieve a cost-effective nZEB. The results show that the highest incentive rate is required for interventions on the opaque building envelope, which are also those that allow the least energy savings. An incentive rate of about 45% for the energy efficiency of the transparent envelope is necessary to reduce the payback time by about 7 years. The efficiency of the plants and the installation of a PV system are energetically and economically convenient even without forms of economic incentive. Finally, if the building is brought to high energy standards—a primary energy saving of 46% and energy class A3—an incentive rate of 40% is required to repay the intervention in about 10 years.

Roadmap to a Sustainable Energy System: Is Uncertainty a Major Barrier to Investments for Building Energy Retrofit Projects in Wide City Compartments?

Along the roadmap to a Sustainable Real Estate-Scape, energy retrofit campaigns on wide city compartments represent a pivotal task, where the importance of the collaboration between the public and private sectors is crucial. Energy retrofit programs on building assets are subject to multiple uncertainty factors (e.g., climate, energy-economy forecasts, etc.) that act as a primary barrier to investment in this field. This paper aims to discuss risk management techniques to understand better how to deal with this kind of uncertainty. The research specifically addresses the techniques of sensitivity analysis and Monte Carlo simulation, focusing first on the phase of variables selection and their probability definition, including climatic, environmental, energy, economic, financial, and stochastic parameters. In this article, it is suggested to include correlation coefficients in the input variables of risk analysis, preferring the two-dimension Monte Carlo simulation to its simple version, since the results are more reliable when separating aleatory from epistemic uncertainty; thus, the results are more reliable. Moreover, it is seen how a sensitivity analysis based on percentile variations of the inputs provides a more accurate representation of risk if compared to the most common sensitivity analysis based on percentage deviations of the inputs. Conducting a sensitivity analysis using percentile variations gives realistic and reliable results, reflecting the tailored definition of uncertainty around the inputs on the basis of specific market analyses or historical series.

Construction Cost Decomposition of Residential Building Energy Retrofit

Buildings are responsible for significant energy consumption and carbon emissions. Green buildings, which incorporate advanced building technologies, offer a solution to reducing energy use. However, high costs associated with green building development present a barrier to widespread adoption. Retrofit projects, involving remodeling, renovation, and redevelopment of existing buildings, offer a viable solution. While prior studies have examined the cost analysis of green and non-green buildings, there is a lack of evidence comparing new and retrofit projects. This study aims to address this gap by providing empirical evidence for the cost decomposition and benefits of new and retrofit projects. Data on energy use, building technology, and costs from 235 certified green homes in the United States were collected, and cost benefits were evaluated. Results show that retrofit projects cost, on average, $1270.5/m2 ($118.0/ft2), which is 30% less than new projects. Land acquisition and development account for 35% of retrofit costs, six times greater than new projects. Excluding land costs, retrofit projects cost, on average, $733.88/m2 ($68.2/ft2), 49% less than new projects. Retrofit projects use similar building technologies as new projects and produce larger energy savings. The cost-benefit values generated by retrofit projects are 86% greater than new projects when considering land costs and 142% greater without considering land costs. These findings contribute to cost management for complex building projects and energy policy for sustainable development. Retrofitting offers great potential to promote the green building movement and suggests effective subsidy programs as a public policy implication.

A Review of Building Energy Retrofit Measures, Passive Design Strategies and Building Regulation for the Low Carbon Development of Existing Dwellings in the Hot Summer–Cold Winter Region of China

Retrofitting buildings to achieve improved levels of energy performance is a key strategy in the transition to a low-/net zero carbon future. In China, there has been an enormous growth in residential construction in recent decades in response to the country’s economic development and population growth. However, although these buildings are structurally solid and have long functional life spans, most have very poor thermal performance. Therefore, they would be very suitable for energy retrofitting. Because of the variety of retrofitting options, it is important to review the retrofit measures, regulations and possible outcomes to find effective, long-term solutions that strike a balance between the energy saved, the carbon emitted and the financial costs over a building’s lifetime. This paper reviews suitable retrofit measures for the hot summer–cold winter region of China, because this is an area with huge numbers of residential buildings that are suitable for energy retrofitting. The study explores the current conditions of targeted residential buildings, retrofit schemes, building regulations, and policy gaps towards achieving China’s 2060 carbon neutrality goal. The review indicates that current mandatory building energy regulations in this region are not ambitious enough to achieve a significantly lower carbon future, and one-step deep Passivhaus retrofit schemes are recommended to achieve decarbonization goals.

Evaluating energy retrofits of historic buildings in a university campus using an urban building energy model that considers uncertainties

Urban building energy model (UBEM) is a powerful tool to simulate performance and evaluate efficiency of upgrades for a group of buildings under the urban context. However, the larger the scale/number of buildings, more parameters must be collected to create energy models that cover each individual building, causing more uncertainties. To reveal this, this study created a UBEM for the mixed modern and historic buildings at a campus in China. The calibrated set of UBEMs with the modeled results meeting the 20% error range, were then used to evaluate uncertainties of energy-savings of four building energy retrofit (BER) measures. The first measure, BER 1, was to preserve the historic values of buildings; BER 2 to meet green building design standard; BER 3 to achieve 20% more savings than BER 2; and BER 4 to utilize renewable photovoltaic energy. For BER 1, BER 2, and BER 3, the energy savings of buildings of different ages varied within 10%–44%. For BER 4, the energy savings of buildings varied within 49%–505%, respectively, where the reason for higher than 100% is energy production is much higher than energy demand. Similar results can be concluded for building functions, for BER 1, BER 2, and BER 3, the energy-saving potentials varied within 6%– 45%, while 97%–492% to BER 4. This study can provide an important and significant reference to apply UBEM in evaluating energy-efficient retrofits as well as other energy-related studies that consider uncertainties.

An Incentives Planning Framework for Residential Energy Retrofits: A Life Cycle Thinking-Based Analysis under Uncertainty

Building energy retrofits can reduce emissions and increase cost savings. Some retrofits that can deliver higher emissions savings are not popular due to a lack of economic justifications. Financial incentives can be used to change buyer perception around such retrofits. This study proposes a framework to identify the best-performing retrofit strategies for a given building cluster and the optimal incentive amounts to promote the chosen strategies, accounting for uncertainties, stakeholder priorities, and budget constraints. The proposed framework was demonstrated using a case study complemented with policy insights. Life cycle cost savings and capital cost significantly impact retrofit purchase decisions. Case study results showed that retrofitting houses heated with electricity can produce significant cost savings. However, adopting energy-conscious behaviours in houses heated with natural gas and injecting renewable natural gas into the gas supply can produce two times more emissions savings achieved by any retrofit strategy applied to an electrically heated house. This indicates the need for adopting performance-based incentives over the prescriptive approach to reward occupant efforts in addition to asset performance. Despite potential life cycle cost savings, incentives must be complemented with low-interest loans to promote retrofit strategies carrying higher capital costs.

How does future climatic uncertainty affect multi-objective building energy retrofit decisions? Evidence from residential buildings in subtropical Hong Kong

Energy consumption of and carbon emissions from buildings, which substantially depend on outdoor climate conditions, may be susceptible to future climate change. However, how future climatic uncertainties affect decision-making regarding building energy retrofits is unclear from the life-cycle analysis perspective. This study used typical high-rise public rental housing buildings in subtropical Hong Kong as a case study to consider future climatic uncertainties under representative concentration pathway scenarios and in different general circulation models to estimate their effect on multi-objective building retrofit decisions considering trade-offs among different objectives, namely, life-cycle economics, life-cycle carbon emissions, and operational energy use impacts. The results indicate the significant influence of future climatic uncertainties on the optimal values of building energy retrofit measures. The passive house infiltration standard and thick (0.06–0.1 m) polyurethane foam insulation can be recommended for long-term future climatic conditions (RCP8.5–2065s). By contrast, optimal values of glazing materials, horizontal shading projection factors, and window-to-wall ratio are not susceptible to future climatic uncertainties. Uncertainties from different general circulation models are another notable factor affecting optimal values and retrofit options. This study reveals the importance of considering future climatic uncertainties when deciding optimal values and selecting building energy retrofit options.

Energy-related financial literacy and retrofits of Soviet-era apartment buildings: The case of Lithuania

This paper extends the literature on energy-related financial literacy by examining its role in collective energy retrofit investment decisions in Soviet-era countries, which suffer from suboptimal levels of these investments, purportedly due to a lack of energy-specific knowledge and financial skills as well as low levels of trust. We investigate whether energy-related financial literacy and trust help explain collective energy retrofit investment decisions of typical Soviet-built multi-dwelling buildings in the case of Lithuania. Using unique survey data from Lithuania, we find that individuals' willingness to invest in multi-dwelling building energy retrofits is positively associated with individuals' general financial literacy, energy literacy, and energy-related financial literacy. Furthermore, we show that individuals' trust in institutions that are directly involved in the house-retrofitting process is an important predictor for multi-dwelling building energy retrofit decisions.

Transparent machine learning models for predicting decisions to undertake energy retrofits in residential buildings

Transparent machine learning models for predicting decisions to undertake energy retrofits in residential buildings

Multi-Criteria Decision Analysis for Energy Retrofit of Residential Buildings: Methodology and Feedback from Real Application

Decision-making in energy retrofit of existing buildings needs to consider the economic and technical criteria, as well as social and environmental ones. The main problems are to define and to aggregate these contradicting issues to support a measurable and verifiable decision process. The working hypothesis of this paper is that the ELECTRE Tri method would respond to the problem. The paper proposes and tests in a real professional environment the ELECTRE Tri method to help choose a retrofit program for collective residential buildings. The evaluation criteria used as performance indicators are defined in consultation with the decision maker and weighted by using the revised Simos’ cards method. The paper proposes to construct the renovation scenarios by combining individual actions that are mutually compatible. The methodology, the proposed criteria and the scenarios were successfully applied on a renovation project of a residential assembly composed of three buildings (67 apartments). A new solution to the problem of defining reference scenarios specific to the ELECTRE Tri method is also proposed. The main advantages of the proposed methodology are the formalization of the decision-making process within the framework of energy renovation strategies and the application of a robust multi-criteria analysis method, considering the complexity of the problem. The main drawbacks are the cost (in time and resources) for obtaining the information needed to construct the decision matrix and the precision of the weights of the criteria. The methodology implemented in Python is available in open source.

An enhanced system for the combined seismic and energy retrofit of masonry buildings

The Italian existing building stock is characterized by low-performance levels in terms of energy efficiency and seismic safety. The development of retrofit solutions fulfilling both targets is therefore of strong interest, as proven by a series of fiscal incentives recently approved, in Italy, to encourage the implementation of both energy and seismic intervention. Nevertheless, energy and seismic retrofitting techniques often present specific features that make it difficult to pursue both objectives. In this framework, an innovative solution is proposed, focused on the enhancement of unreinforced masonry buildings using expanded-clay blocks infill walls. Expanded-clay block walls technique has proven to provide excellent energy performance and ensure high seismic safety in new buildings. This technique's feasibility and efficiency as a retrofit solution were analysed when applied to a representative case-study building, analysed in the current condition and after the application of the retrofit system. Dynamic thermal simulations were carried out to evaluate the hygrothermal performance, showing a general decrease in the overall thermal transmittance and an improvement in the indoor thermal comfort for the retrofitted configuration. The seismic behaviour was assessed according to actual standards, showing an increased capacity of the building towards horizontal actions post-retrofit application.

Feasibility study of the UXindoor framework in two public office buildings: A standardized approach to scoring indoor user experience with qualitative and quantitative techniques

A human-centered strategy is crucial for effective energy retrofits, as the subjective experience of occupants directly affects the energy performance of buildings. To address this, we introduce UXindoor, a standardized scoring framework for assessing the User eXperience (UX) of Indoor Environmental Quality (IEQ). UXindoor is a key component of the PRIME Energy-Indoor project, which aims to guide integrated building energy retrofits based on real energy usage and IEQ data. The framework utilizes questionnaires, handheld instruments, and IoT environmental sensors in a unitary assessment framework. This feasibility study presents the results of the pilot-testing of the framework in two public buildings in Thessaloniki, Greece over a six-month period from September 2022 to February 2023. The study discusses the advantages of the proposed system as well as its limitations.

The cost overrun of depopulation to improve energy efficiency in buildings: A case study in the Mediterranean Region

The implementation of energy efficiency measures in public buildings is a complex process that hinges on multiple factors. A factor relevant for some European regions is their ongoing depopulation. In these regions, building energy retrofitting presents additional challenges to those in urban areas, such as over-dimensioned public buildings and low occupancy levels. This work analyses these challenges in the province of Teruel (Spain), one of the regions with the highest depopulation levels in Spain. To this end, a methodology has been developed to assess the effect of depopulation on the cost of upgrading public buildings to improve their energy efficiency. The results show that the investment required per inhabitant for building retrofitting is approximately four times as high in depopulated areas as in urban areas. Furthermore, the low occupancy levels of public buildings can triple the payback time of some energy efficiency measures. To overcome these barriers, in addition to specific policies for depopulated areas, energy planning is essential. An adequate action plan, combining the implementation of energy efficiency measures and the integration of renewable energies in buildings, is the most effective tool to improve the sustainability of public buildings circumventing the barriers created by depopulation.

An impulsive and switched system based maintenance plan optimization in building energy retrofitting project

The maintenance time schedule optimization into the investment budget decision for building energy retrofitting and maintenance planning is incorporated. The aggregate performance and population dynamics of the totality of retrofitted items is described by an impulsive switched system model. The items are switched to different working states by maintenance actions with impulsive effects. Considering the retrofitting project with deterioration. The objective of optimal maintenance control is to maximize the overall energy savings and financial payback. The optimal maintenance control problem is showed to be feasible and bounded. The maintenance time schedule and intensities are simultaneously optimized by an improved differential evolution (DE) algorithm. Compared with the fixed maintenance time schedule, the proposed approach is validated by simulation results, specifically, 3.36% of energy saving and 23.09% of internal rate of return (IRR) can be improved.

Building energy retrofit simulation for exploring decarbonization pathways in a community-scale food-energy-water-waste nexus

• A food-energy-water-waste nexus analysis can aid in low carbon city design • System dynamic modeling analysis synthesizes low carbon city initiative. • Scenario planning helps identify decarbonization pathways for prioritization. The retrofit of existing buildings at a community scale can provide a huge opportunity to reduce the community's energy consumption and subsequent greenhouse gas (GHG) emissions in support of the United Nations agenda for net-zero emissions and decarbonization. This study demonstrates a community-scale food-energy-water-waste nexus through 6 scenarios (A1–A6) by highlighting decarbonization pathways with system dynamics modeling. Several potential retrofit alternatives are proposed for analyzing building energy consumption, energy requirements for rooftop or greenhouse crop production, and potential energy and water savings from renewable energy harvesting. Such a nexus analysis is designed to integrate (1) building energy consumption, (2) waste management and water consumption, and (3) GHG emissions based on life-cycle assessment to prioritize scenarios. The incorporation of solar photovoltaic (PV) systems (i.e., rooftop, parking lot, parking garage, and floating solar PV) sustains approximately 72% of net energy demand (scenario A3), while the integration of all solar, wind, and anaerobic digestion alternatives provides around 41% of net energy demand (scenario A6). It is vital to emphasize decarbonization pathways through the use of renewable energy by 2030 in scenario A5 (i.e., solar and wind energy) and A6, both of which avoid energy consumption from the utility grid and result in 250% total carbon emissions offset.

A multi-aspect approach to energy retrofitting under global warming: A case of a multi-apartment building in Montenegro

Global warming will seriously affect buildings, and the Montenegrin building stock is no exception. Since the country is one of the most inefficient energy users in Europe, improving the energy efficiency of buildings is essential. Therefore, the study implemented a novel multi-aspect approach to energy retrofitting, linking building thermal performance, occupant interaction and climate change. A representative existing multi-apartment building in Podgorica was selected, and a survey among occupants was conducted to identify their satisfaction with indoor thermal comfort and to evaluate the acceptability of the proposed energy retrofit measures. Next, the thermal performance of the building was simulated under current and future climate conditions. Finally, a comprehensive parametric analysis was performed by applying different retrofit scenarios. The selected retrofit measures were evaluated based on their impact on energy efficiency and occupant acceptability. The results showed that the most impactful retrofit measure would be thermally insulating the building envelope, followed by a lower shading set-point and natural ventilation cooling. Applying the best retrofit combinations would reduce the total energy demand by 75% under the current climate and by 66% and 59% at the end of the 21st century under the RCP4.5 or RCP8.5 scenarios, respectively. However, the occupant survey results disclosed that beyond thermally insulating the building, occupants have limited awareness about the potential of energy retrofit actions, while summer thermal discomfort is the dominant issue. Therefore, building energy retrofit and climate adaptability actions should also address occupant views.

Energy Retrofitting Assessment of Public Building Envelopes in China’s Hot Summer and Cold Winter Climate Region

The retrofitting of existing public buildings to save energy and reduce carbon emissions is a priority for China’s building sector. Accordingly, the Chinese government requires all public buildings to be energy retrofitted based on the Design Standard for Energy Efficiency of Public Buildings GB50189-2015. However, few studies have been conducted to assess the energy efficiency of this design standard in the hot summer and cold winter (HSCW) climate region of China. The aim of this study was therefore to provide sensitivity analysis for the thermal properties of the envelope of a typical public building energy retrofit in China’s HSCW climate region. The results show that the thermal performance of the existing envelope of the sample building was very poor, with heating and cooling energy consumption 18.94% higher than the GB90189-2015 baseline model. It was found that better optimized parameters could reduce the heating and cooling energy load by 28.26% compared with the parameters of the sample building. The findings from this study provide valuable references for local governments and practitioners eager to improve the energy efficiency of existing public buildings in China’s HSCW region.

Improved calibration of building models using approximate Bayesian calibration and neural networks

Deep energy retrofits of buildings are crucial to meeting climate targets and depend on calibrated energy models for investor confidence. Bayesian inference can improve the rigour in standard practice and improve confidence in calibrated energy models. Approximate Bayesian computation (ABC) methods using neural networks present an opportunity to calibrate energy models while inherently accounting for parameter uncertainty, and face less computational burden than the current standard process for Bayesian calibration. A case study for a large, complex building is presented to demonstrate the applicability of ABC and parameter sensitivity screening is found to result in over-confidence in the resulting inference by between 14% and 85%. Finally, the presentation of posterior distributions as independent distributions may be misleading, which can misattribute the true likelihood of parameters. Highlights Implementation of an Approximate Bayesian Computation method incorporating the Sequential Monte Carlo algorithm with a neural network surrogate model. A comparison of Bayesian inference with standard practice. An investigation of sensitivity screening for parameter selection on the inference results. Application to a complex multi-zone dynamic energy model of a large retail building.

Analysis of COVID-19 crisis-related building energy retrofit incentives in Italy

The advent of the COVID-19 pandemic led to an economic crisis of the construction industry and to an increasing of energy consumption in the residential sector for all the world. The European Union highlights the crucial role of building sector for both energy gains and economic growth, defining a “Renovation Wave” plan combining regulation, financing and technical support with the aim of greening the buildings, creating jobs and improving lives. In Italy a great support mechanism for energy refurbishment of existing buildings has been launched by means of tax deduction of 110% over 5 years. The present study aims to analyze this new funding mechanism, under energy, environmental and economic point of views. By means of a real case study, representative of highly widespread southern Italy HVAC-building system, it will be highlighting advantages and contradictions of the incentive mechanism developed, proposing possible future improvements. It is found that, if on one hand, the best refurbishment measure under energy/environmental point of view is the external insulation, windows replacement, electric heat pump and PV-system installation, with a global not renewable performance index reduction of 81%, on the other hand it is not the best solution considering the cost/saving ratio.