Energy Efficiency Retrofit Research Articles

Applying the response surface methodology to predict the energy retrofit performance of the TABULA residential building stock

Recent advances in computing software have enabled the development of calibrated building energy simulations tools that allow retrofit-related analysis including optimization and energy-efficient building design. However, to create a national energy and climate plan, using these tools may imply a great deal of effort (time, cost, and human resources) to carry out simulations for the full set of different building types, construction, geometries, design parameters, and retrofit scenarios. Because of this, simplified approaches that can reliably estimate the impact of energy-efficiency retrofit alternatives based on averaged building stock characteristics could offer a significant advantage, especially in middle-income countries such as Bosnia and Herzegovina. This study aims to explore the energy reduction potential of a representative building from the national residential building stock by utilizing the response surface methodology (RSM). In this study, RSM is combined with the energy simulation tools EnergyPlus and DesignBuilder to model the energy savings associated with energy-efficient retrofit measures for a residential building from the national TABULA registry in Bosnia and Herzegovina. This study introduces a novel energy consumption model that can be applied to optimize energy-efficient retrofit design solutions for reducing the energy consumption for heating and cooling in the residential building sector. Moreover, the model developed was validated by using the results of a national survey on energy consumption in Bosnia and Herzegovina. Therefore, the use of the model developed is versatile and suitable for rapid prediction of energy-efficient retrofit-related energy consumption and energy savings of the residential building stock.

Tripartite Evolutionary Game Analysis of Stakeholder Decision-Making Behavior in Energy-Efficient Retrofitting of Office Buildings

Environmental degradation is significantly influenced by the construction industry. Energy-efficient retrofitting of existing office buildings has become an effective means of reducing building energy consumption. Implementation of retrofits requires the support and cooperation of stakeholders. However, existing studies on the dynamics of decision-making behavior among stakeholders are still relatively limited. This study constructed a tripartite evolutionary game model including the government, property owners, and end users, to better understand the behavioral evolution and evolutionary stabilization strategies of stakeholders. The results show that: stakeholders’ decision-making behavior has obvious mutual influence; benefits and costs are the dominant factors in stakeholders’ decision making; the effects of government supervision policies depend on the profitability of the project; and government behavior appears to be influenced by public willingness. In addition, targeted countermeasures were proposed for the development of the energy-efficiency retrofit market. This study provides a generic model that fits various contexts and can be used to inform a reference for scientific decision making by stakeholders.

The actual performance of retrofitted residential apartments: post-occupancy evaluation study in Italy

ABSTRACT Housing retrofits are undertaken to reduce energy use and to improve ‘occupants’ indoor environmental conditions. Despite increased retrofitting of the Italian housing stock, there is a lack of data on their energy use and indoor environmental quality (IEQ). This paper fills this gap by a post-occupancy evaluation (POE) study of seven retrofitted apartments in northern Italy; a non-retrofitted case study was included as a comparison. The study aimed to understand aspects of IEQ and occupant satisfaction after energy-efficiency retrofits. A mixed-method approach encompassed occupant satisfaction surveys, energy bill comparisons, in-situ indoor air temperature, and relative humidity measurements. Results highlighted ‘occupants’ thermal comfort improvement and heating energy consumption reduction after retrofits. Furthermore, reported preferred indoor temperatures w within a broader range than the recommended Italian regulations and CIBSE guide A standard. However, some participants reported unintended consequences, including mould growth and noise from the mechanical ventilation system. This study shows the potential of POE to understand the actual performance of retrofitted residential buildings. However, the difficulties of conducting a POE in retrofitted existing residential buildings show the need of further research on how to effectively conduct POE in retrofitted residential buildings, including improved digital quality monitoring methods.

Estimating Space-Cooling Energy Consumption and Indoor PM2.5 Exposure across Hong Kong Using a City-Representative Housing Stock Model

High-quality data on building energy use and indoor pollution are critical to supporting government efforts to reduce carbon emissions and improve the population’s health. This study describes the development of a city-representative housing stock model used for estimating space-cooling energy use and indoor PM2.5 exposure across the Hong Kong housing stock. Archetypes representative of Hong Kong dwellings were developed based on geographically-referenced housing databases. Simulations of unique combinations of archetype, occupation, and environment were run using EnergyPlus, estimating the annual space-cooling energy consumption and annual average PM2.5 exposure concentrations under both non-retrofit and retrofit scenarios. Results show that modern village houses and top-floor flats in high-rise residential buildings, on average, used 19% more space-cooling energy than other archetypes. Dwellings in urban areas had lower exposure to outdoor-sourced PM2.5 and higher exposure to indoor-sourced PM2.5 compared to those in rural areas. The percentage decrease in space-cooling energy consumption caused by energy efficiency retrofits, including external wall insulation, low-e windows, and airtightening, varied significantly based on archetype. The implementation of external wall insulation in the housing stock led to an average decrease of 3.5% in indoor PM2.5 exposure, whilst airtightening and low-e windows resulted in 7.9% and 0.2% average increases in exposure, respectively.

Methods on reflecting electricity consumption change characteristics and electricity consumption forecasting based on clustering algorithms and fuzzy matrices in buildings

The extraction and analysis of electricity consumption changing patterns are increasingly important, as they can guide in energy management and efficiency retrofitting. Consequently, it is necessary to extract the laws governing building electricity consumption characteristics. This method should be on an hour-scale and successfully applied online to various buildings. Under these conditions, the method should be as simple as possible to ensure excellent online applications. A matrix model method was developed based on the conventional K-nearest neighbour clustering algorithm, which introduced the concept of electricity intensity levels. This method used the slopes of the power consumption curve as the grading standard for the extraction and assessment of the electricity consumption laws. The validation results for seven different buildings with various functions and climate zones, including the mean absolute error, mean absolute percentage error, mean square error, root mean square error, and coefficient of variance, showed that this method met the aforementioned requirements. Moreover, this method can be used for power consumption prediction, which integrated a process of filtering historical data, leading to better accuracy and less data volume than that of other methods that use historical data for prediction. Practical application This paper proposed a matrix model method based on the conventional K-nearest-neighbour clustering algorithm, which introduced the concept of electricity intensity levels. This method was applied to various buildings online, which coupled the process of filtering historical data and flexible selectivity of models when used on different buildings. This method was used for assessing energy-saving potential, energy-saving retrofit priorities, and power consumption forecasting, which will benefit researchers and engineers.

An Investigation of Occupants’ Energy Perceptions in Energy Efficient Retrofitted Residential Buildings: A Review Paper

Buildings are the main sector in energy consumption and CO2 emissions. Retrofitting of existing building has been identified as one of the significant strategies for reducing the impacts of buildings on energy and environment. However, recent studies have shown that low energy buildings mostly do not perform as expected. These differences are related to different factors including the interaction between occupants and building technologies. Thus, most renovation initiatives have not considered occupant behavior equally to the energy efficiency process. Many of the existing studies have been focused on technological improvements rather than behavioral-related parameters. Hence, this study aims to review the literature on the occupants’ energy perceptions and their behavioral interventions in energy efficient retrofitted residential buildings. The results of the literature review reveal that household’s energy consumption significantly differs according to the various factors including social-economic, cultural, household composition as well as individual attitudes, habits, experiences, and occupant practices. Moreover, the energy consumption in the residential sector is highly dependent on demographic parameters. The demographics factors are classified according to type of family, level of income, age of the occupants, and individuals’ educational status. The findings shows that energy perception gap formulates the energy behavior and it is related to the lack of personal interest, accurate information and individuals’ awareness about how to consume efficiently. Therefore, it is suggested that the level of occupant’s perception on energy, control, or comfort have to be considered during energy efficiency retrofits. The study contributes to understanding of occupants’ behaviors which cause energy performance gap and enlighten approaches to encourage more energy efficient behavior.

Active and Passive Solutions for an Energy Efficient Building

In addition, the majority of electricity consumed in buildings (58%) should come from renewable sources. Together with solar thermal, modern biomass, and district heating, overall renewables could ramp up to 81%, from 36% today’s contribution for the sector. Nonetheless, to materialize these predictions, a global investment of around USD 32 trillion (28 trillion euros) is expected between now and 2050. In the European Union, the nearly zero-energy building standard (nZEB) will be obligatory for all new buildings by 2021. Although the increase in energy demand will be reduced with this measure, it does not really affect the energy consumption at present. It is imperative to design energy efficiency retrofit and renovation financing schemes. For many years to come, only measures taken in existing buildings will have a significant effect on the total energy demand in the building stock. Firstly, this work presents a brief analysis of active and passive solutions for an energy-efficient building. Secondly, in this work it identified a set of active and passive solutions, which, in a combined way, develop the thermal performance of a residential building, allowing it to become energetically autonomous. The program EnergyPlus was used to execute the thermo-energetic simulations for the diverse scenarios considered, in the study case. The numerical results showed that the implementation of passive solutions improves the energy performance of the buildings, and the use simultaneously of an active solution, a renewable energy source, allows the reach of the energy-autonomous of the building.

Energy-Efficient Retrofitting under Incomplete Information: A Data-Driven Approach and Empirical Study of Sweden

The building performance simulation (BPS) based on physical models is a popular method to estimate the expected energy-savings of energy-efficient building retrofitting. However, many buildings, especially the older building constructed several decades ago, do not have full access to complete information for a BPS method. Incomplete information generally comes from the information that is missing, such as the U-value of part building components, due to incomplete documentation or component deterioration over time. It also comes from the case-specific incomplete information due to different documentation systems. Motivated by the available big data of real-life building performance datasets (BPDs), a data-driven approach is proposed to support the decision-making of building retrofitting selections under incomplete information conditions. The data-driven approach constructed a Performance Modelling with Data Imputation (PMDI) with integrated backpropagation neural networks, fuzzy C-means clustering, principal component analysis, and trimmed scores regression. An empirical study was conducted on real-life buildings in Sweden, and the results validated that the PMDI method can model the performance ranges of energy-efficient retrofitting for family house buildings with more than 90% confidence. For a target building in Stockholm, the suggested retrofitting measure is expected to save energy by 12,017~17,292 KWh/year.

Integrated retrofit solutions for improving the energy performance of historic buildings through energy technology suitability analyses: Retrofit plan of wooden truss and masonry composite structure in Korea in the 1920s

Building energy consumption and carbon emissions must be reduced to decrease the rate of global warming. To improve the energy efficiency of historic buildings, energy retrofitting can serve as an effective strategy. Retrofitting historic buildings is difficult due to the conflict between the historical value and usefulness of the building, but a modern scientific approach can help ensure that valuable historical records and artifacts remain protected and available. In addition, the retrofit of historic buildings can contribute, although a small part, to reducing carbon emissions nationally, and can have a symbolic meaning as a combination of history and modernity.This paper proposes a package of appropriate measures to improve energy efficiency, reduce the energy consumption of buildings, and preserve regularly used historic buildings for 100-year-old wooden truss and masonry composite structured historic buildings in Korea. The proposed measures are applied to most historic buildings in Korea built in the 1920s and have the potential to improve building performance. A new approach to applying energy technology to historic buildings is proposed. The energy application suitability analysis process was established by integrating three analysis techniques: the energy-saving effect analysis technique, historical value impact evaluation technique, and economic analysis technique. To achieve an appropriate retrofit plan, the condition of a building was evaluated through on-site diagnosis. Thermal transmittance rate assessments, temperature, and humidity monitoring, and infrared thermal imaging analyses were performed to evaluate the building's condition. Consequently, thermal transmittance rates for the wall and roof of the historic building were 1.18 W/m2K and 1.67 W/m2K, respectively, which indicated a risk of excessive energy consumption and condensation. Then, the suitability of each energy technology was evaluated by analyzing its economic feasibility and impact on the historical value and by simulating the reduction in energy consumption of the building. Thereafter, based on the analyses, the energy technologies deemed suitable were integrated to form an energy-efficient retrofit package, and an appropriate solution was elucidated. In conclusion, the package with the lowest impact on the historical value and the highest energy reduction decreased the total energy consumption by 15.9%. According to the results of this study, the process and package solutions proposed in this study are appropriate measures for historic buildings built in the 1920s in Korea, and can be a strategy with the potential to reduce carbon emissions and energy.

Evaluation of energy-saving retrofit projects of existing rural residential envelope structures from the perspective of rural residents: the Chinese case.

The existing residential envelope in rural areas has low energy efficiency, with low energy utilization and serious energy waste for winter heating. However, in recent years, farmers have not undertaken energy efficiency retrofit projects for existing buildings in rural areas. This study proposed an evaluation model based on the logistic-AHP-TOPSIS method from the perspective of farmers. First, this study conducted a questionnaire survey of 208 rural households and used logistic models to determine which existing evaluation indicators significantly impact farmers' willingness to participate in energy efficiency retrofit projects. Second, the weights of the eight indicators were determined using AHP. Finally, this study evaluated the retrofit program of a case in Gansu Province using the TOPSIS method. In the analysis, total investment, annual winter heating costs and energy efficiency improvements were found to be the most important factors for farmers. The highest score for existing buildings was 0.3747 because there is no additional investment required; the option of partial retrofitting according to the actual needs of households scored 0.3350 because it balances economic performance with energy efficiency performance; The entire retrofit program has the highest investment and a long payback period, and its score is the lowest with 0.2904. Furthermore, the study recommended that a self-build and self-repair organization led by village collectives be developed to unify the retrofit design and construction and lower renovation costs. Bulk purchases could enable farmers to increase their power in negotiations.

Evaluation Method on Energy-Efficient Retrofitting of Wooden Walls of Chinese Traditional Dwelling—A Case Study of Rendetang in Jinhua

Traditional wooden dwellings, which are widely distributed with enormous stocks in China, are of great historical and have obvious cultural value. The walls of such buildings are generally subjected to poor thermal insulation performance, which not only reduces residential thermal comfort but also increases building cooling and heating energy consumption. In addition, buildings of this type have been subjected to all kinds of problems, such as the lack of measures for improving thermal comfort and the shortage of special funds. Consequently, it is very challenging to reutilize Chinese traditional dwellings, many of which are abandoned and even collapsed. All of the above have become major difficulties encountered in the traditional dwelling heritage protection. Hence, investigating the energy-efficient retrofitting strategies for traditional dwellings and giving economical evaluation methods are two keys to solving the reutilization problem of traditional dwellings. Against this background, a set of second-level evaluation methods for the energy-efficient retrofitting of Chinese traditional dwellings are proposed in this research, including the survey on retrofitted dwellings, the retrofitted dwelling modeling and energy consumption analysis, the definition of wall retrofitting scheme, the first-level evaluation of dwelling retrofitting, the second-level evaluation of dwelling retrofitting, and the screening of the wall retrofitting scheme. The first-level evaluation, which took energy efficiency as a reference index, could evaluate the energy conservation effect before and after dwelling retrofitting. With the payback period as the reference index, the second-level evaluation could assess the overall economic efficiency of dwelling wall retrofitting. An appropriate dwelling wall retrofitting scheme could be screened by integrating first-level and second-level evaluation indexes. Then, this scheme was applied to evaluate the wooden wall retrofitting scheme of a typical traditional dwelling in Yapan Village, Zhejiang Province, China. It was discovered through a comparative analysis that if used to reconstruct dwellings in Zhejiang and other places, the combined materials of XPS board and wood-bamboo could not only effectively improve the energy efficiency but also has good economic efficiency. Meanwhile, problems such as the condensation of wooden walls and their construction thickness could be solved by controlling the material thickness. The above research is of guiding significance for the energy-efficient retrofitting of traditional wooden dwellings in the hot-summer and cold-winter zone of China, and moreover, it can provide reference for the energy-efficient retrofitting of traditional wooden dwellings in other climate zones of China.

Potential and roadmap of CO2 emission reduction in urban buildings: Case study of Shenzhen

Buildings play an increasingly important role to determine the trend of CO2 emissions in cities. Whether CO2 emissions from buildings can be effectively mitigated has great significance for cities to achieve climate governance goals. The study takes Shenzhen, a China's megacity, as an example to examine how the penetration of newly emerging clean technologies and consumer-to-prosumer role transition of buildings will contribute to CO2 emission reductions. Based on a Low Emissions Analysis Platform (LEAP) model, the major results indicate that CO2 emissions of Shenzhen's building sector could be capped by 2022–2025 and substantially decreased by more than 60% by 2030. Accelerating energy efficiency retrofitting of existing buildings and enforcing stricter design standards on new buildings could largely reduce CO2 emissions, but still unable to prevent them from growing. The intensification of building energy-saving management and promotion of distributed renewable energy use would bring additional potentials of emission reduction, enabling a peak-reaching and a rapid downward trend of building emissions. To achieve the potentials, close cooperation and synergic efforts between multiple stakeholders are advocated for establishing intelligent energy-saving management systems, decarbonizing urban power supply, and popularizing distributed rooftop photovoltaic power stations.

A Systematic Review of Associations between Energy Use, Fuel Poverty, Energy Efficiency Improvements and Health.

Energy use in buildings can influence the indoor environment. Studies on green buildings, energy saving measures, energy use, fuel poverty, and ventilation have been reviewed, following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The database PubMed was searched for articles published up to 1 October 2020. In total, 68 relevant peer-reviewed epidemiological or exposure studies on radon, biological agents, and chemicals were included. The main aim was to assess current knowledge on how energy saving measures and energy use can influence health. The included studies concluded that buildings classified as green buildings can improve health. More efficient heating and increased thermal insulation can improve health in homes experiencing fuel poverty. However, energy-saving measures in airtight buildings and thermal insulation without installation of mechanical ventilation can impair health. Energy efficiency retrofits can increase indoor radon which can cause lung cancer. Installation of a mechanical ventilation systems can solve many of the negative effects linked to airtight buildings and energy efficiency retrofits. However, higher ventilation flow can increase the indoor exposure to outdoor air pollutants in areas with high levels of outdoor air pollution. Finally, future research needs concerning energy aspects of buildings and health were identified.

Policy Development for Initiating Green Universities in Sri Lanka: A Case Study Based on the NSBM Green University

The higher educational institutes expand their scope of operational capacities while enhancing the accountability and sustainability in the terms of environment. Similar to the government conventional universities, recently oriented private institutes consecutive to develop the strategies and projects related to green technology. The green campus concept allows operating main functions of the institute, students and staff to utilize energy and resource in sustainable manner. In this paper addresses policies that have initiated to use the resource and energy efficient, the problems occurred during the development of green campus, analyzes based on the impact of the green area to reduce carbon foot print and possible approaches that can be used from other international Green Universities. The study selects NSBM Green University as the location. NSBM Green University is one of the green universities in South Asia and sets an example for the whole South Asia by paving the way for environmental sustainability. The main objective of the study is to identify the potentials of NSBM green university under the framework of green technology. On other hand, the investigation focuses attention on three main scopes namely; reduction of the carbon foot print by expanding the green area, by introducing eco-friendly power generation units and consisted of waste disposal. Meanwhile, the study tries to address the policy framework of the NSBM Green University to promote environmental friendly life style among the university staff and students. The strategies depict application of efficient technologies, and university resource management policy initiatives. The research adopts a case study approach to initially and in depth analysis related to the contextual insights of policy development in the NSBM Green University. The study emerges efficient action cores of energy and resource utilization; it further saves land, energy, water, material and environment protection. The study identifies the attributes like demonstrating green buildings, demonstrating energy efficiency retrofits, demonstrating renewable energy applications, demonstrating energy saving management and finally introducing energy saving management systems. Besides, study reveals NSBM University can strive for a positive reputation through the implementation of the green technology. High level of initiative ideas, sensitive of students for the green campaign and enforcement of the government to motivate for altering green concepts are synthesized in the study as the main results. As the conclusion green master plan is cooperated with green education, culture and activity in the institute.
 Keywords: Green university, Policy, Energy

Re-considering the energy efficient retrofitting approach to question cost-optimality and nZEB under COVID-19 measures

The building energy performance has been highly studied in the last decades considering the indoor environmental quality, and sustainability indicators to examine energy-efficient cost-optimal, and nZEB building levels for different building typologies. However, since the start of the COVID-19 pandemic in 2020, the usage and operation of public spaces and buildings have evolved according to COVID-19 measures produced by the authorities. Social distancing measures and HVAC system measures affecting energy performance and indoor environmental quality of the public buildings are consequently necessary for building energy performance studies. Thereby, it is aimed at re-considering an energy-efficient cost-optimal retrofitting approach for a primary school building case, under the COVID-19 measures to recast an energy-efficient cost-optimal level and apply a cost-efficiency criterion to search for the measures adapted nZEB scenarios. COVID-19 measures affecting building energy performance, such as social distancing and IEQ requirements, were analysed. Then, probable ventilation rates were controlled by the infection probability method to satisfy the limit number for infection. Thus, pre-COVID-19 and post-COVID-19 variables regarding occupancy density and HVAC operation were determined for the calculation process. Besides, retrofit scenarios were shaped to improve optic and thermophysical properties of the façade, lighting, and HVAC systems performance. Then, energy, LCC, thermal comfort and IEQ performance of retrofit scenarios were calculated with a calibrated model. Results were evaluated by applying the cost-efficiency criterion to find out nZEB scenarios. It can be stated that distinct LCC and energy use increments occurred in the cost-optimal range and nZEB level.

A Systematic Review of Energy Efficiency Home Retrofit Evaluation Studies

We systematically review studies evaluating the energy savings and cost-effectiveness of residential energy efficiency retrofit programs. We review 39 evaluations of 23 residential retrofit programs that were evaluated between 1984 and 2021. Our sample is restricted to program evaluations that used postretrofit household energy billing or consumption data from 140,977 retrofitted households. We report four primary findings. First, none of the studies in our sample reported deep energy savings (e.g., 50% or greater) from retrofit programs. The mean reduction in measured electricity and/or fuel consumption due to energy efficiency retrofits for all programs included in our sample was roughly 7.2%. However, because many households use both fuel and electricity, total household energy savings from the retrofit programs evaluated in our sample are probably smaller. Second, reported program savings decreased as the internal validity of study design increased. Third, as measured by realized savings and cost-effectiveness, the most promising retrofits were insulation and programmable thermostats, whereas the least promising retrofits were storm windows and doors. Fourth, programs with high reported savings and low costs of conserved energy served low-income, fuel-heated households exclusively.

Global Research Trends on Energy Efficient Retrofitting in Existing Buildings

Built environments have destructive effects on the natural environment as one of the responsible actors in increasing energy consumption and greenhouse gas emissions. Therefore, all types of energy-efficient and sustainable improvement studies for the existing building stock are pivotal in reducing the adverse effects on the environment. Although the measures taken and targets determined in line with the policy regulations implemented on a global scale are promising, the proliferation rate of these practices is relatively low. The retrofit process's complex nature, which requires multi-dimensional solutions involving several aspects, increases the significance of relevant studies. In this context, it is thought that it will be beneficial to monitor, analyse and assess contemporary studies in determining the areas that require further research. This study presents a comprehensive literature analysis using the science mapping method using bibliometric data of qualified academic studies published since 2000 when research on the energy-efficient retrofit of existing buildings gained momentum. It aims to contribute to the literature by determining the research areas in which the contemporary research concentrates and evaluating future studies on "energy efficient retrofit of existing buildings".

Retrofitting Old Silk Factory in Valmadrera, Italy with Insulated Envelope Solutions.

Building industry is responsible for almost 50% of the world’s total energy demand. It takes more energy to operate buildings than it takes to run the manufacturing or transportation industry. In the drive for climate change, a lot of work is being done by policy makers for making new projects better aligned with environmental and energy conservation goals. It is not enough to only focus on improving the climate response of new construction. Work also needs to be done on improving the energy performance of existing building projects which will in turn, further reduce the CO2 footprint of the building operations industry. One way to reduce the energy consumption of existing buildings, is to add insulation to façade elements during building retrofitting projects. The purpose of this research is to shed light on probable options and benefits for adding insulation to traditional envelopes. This will enhance the operating capacity of buildings without the need for demolition or re-construction. This project demonstrates the energy efficient retrofitting of an old silk factory in the historic city of Valmadrera, Italy to act as a prototype project testing suitable options for adding insulation to existing structural systems. One of the biggest challenges for this type of upgrade is the porous nature of the existing building material and how it conflicts with the hygroscopy of synthetic insulation materials. The research suggests the use of organic insulating materials for the envelope elements. At the same time it also offers valuable suggestions for future explorations. This research has a high impact value globally, due to the vast treasure of historical architecture buildings which need to be preserved, but also need improvement in terms of their technological performance. Furthermore, it holds strong relevance for the Saudi Vision 2030 because preserving local architectural practices, materials and techniques is a significant part of the national motivation to preserve Saudi cultural identity.

Possibilities for Deep Renovation in Multi-Apartment Buildings in Different Economic Conditions in Europe

This paper analyzes the potential for deep renovation of an apartment building to the level of a passive house in different contexts in the continental part of Europe. The examined variables include different local climatic conditions, levels of economic development, and levels of market development (energy prices, energy footprint, labor prices, etc.) as well as different energy efficiency retrofit scenarios in four different countries. The adequate methodology was developed here in order to obtain an optimal solution for deep renovation in each context. The proposed methodology was based on the interaction of energy simulation and mathematical optimization. In this model, the energy performances of a building are determined with the EnergyPlus package and the optimal solution was obtained by using a mixed-integer non-linear programming model. The results demonstrate that the optimal solution for each analyzed location cannot provide cost-effectiveness over the lifetime of a building, so the introduction of additional subsidies or incentives, such as carbon taxes and upfront subsidies, is necessary.

Energy retrofit and passive cooling: overheating and air quality in primary schools

While building stock modelling has been used previously to investigate the space heating demand implications of national energy efficiency retrofitting, there are also implications for indoor overheating and air quality, particularly in schools, with highly intermittent occupancy patterns. This paper assesses indoor overheating risk and air quality within an English classroom stock model containing 111 archetypes, based on the analysis of the nationwide Property Data Survey Programme (PDSP) containing 9629 primary school buildings in England. Metrics for indoor temperatures, heating demand and concentrations of three contaminants (CO₂, NO₂, PM_2.5) were estimated in naturally ventilated classrooms, while exploring future climate projections, retrofit and overheating mitigation scenarios to analyse school stock resilience. Classrooms with a south-east orientation experience around four to six times the overheating-hours compared with those with a northern orientation. Post-1976 archetypes are most susceptible to overheating, indicative of the conflict between better insulated and airtight classrooms and overheating prevention. A range of retrofit and passive cooling measures can mitigate against overheating alone, although mechanically driven cooling and filtration may be required towards the 2080s. While no single measure predicted universally positive effects for building performance, night ventilation and overhangs were found to be particularly effective passive overheating mitigation methods across the school stock. <em><strong>Policy relevance</strong></em> With around 30% of their waking hours spent in classrooms, English schoolchildren experience greater vulnerability to higher indoor temperatures and air pollutants than adults due to limited thermoregulation and immunity, with additional impacts on cognitive performance. An increased risk of overheating (due to a warming climate) necessitates the development of future overheating mitigation policies and strategies, which could directly impact separate retrofit strategies required for energy demand reduction. Airflow network modelling has demonstrated how such measures could contribute to school sector carbon emissions. While the granularity of national datasets represents a hurdle to predictive modelling, the orientations, geographical regions and construction eras most vulnerable to overheating risk have been identified. Building stock-level modelling could thus be used to identify sectors of the stock most vulnerable to overheating and poor air quality, leading to strategies with more targeted solutions, including the use of alternative cooling strategies to air-conditioning.