Energy Retrofit Solutions Research Articles

Energy Analyses and Optimization Proposals for Hotels in Sicily: A Case Study

The recent post-pandemic period has economically affected many business sectors. One of these is the hotel industry. As a result of this economic crisis, it is necessary to act on the economic costs of running energy-intensive buildings such as a hotel. The thermal and electrical energy consumption of an accommodation facility weighs heavily on the economic balance. Governments around the globe have moved to help those activities in need. To improve the sustainability of the hospitality sector from an environmental and economic point of view, the introduction of energy retrofit solutions is mandatory. Following European sustainability laws, the impact and efficiency of the building were calculated using smart readiness indicators. The purpose of this paper is to present a case study of a 5-star hotel located in southern Italy characterized by high energy consumption. Precisely these consumptions are due to air conditioning, lighting, hot water, catering, and all other utilities. The entire building and the systems serving it were characterized by means of software that studies consumption with dynamic models, Trnsys. The same software made it possible to model the case study by replacing the existing air conditioning system with one supplied by renewable energies. Two energy retrofit hypotheses were chosen to obtain the best economic and environmental results. First, the choice was to install solar cooling powered by flat solar panels, and the second choice was solar cooling powered by evacuated tube collectors. This paper reports the technical and economic characteristics of both proposed solutions, quantifying the energy and economic savings to identify the best solution.

Modelling and simulation of low-risk energy retrofit measures for Traditional Listed Dwellings in the UK

The UK owns the oldest dwellings in Europe. Most of them have special historic and/or architectural value but low energy performance and are responsible for high operational carbon emissions. Energy retrofit of this part of the stock is much needed but problematic, due to the risks associated with altering their complex thermo-hygrometric behavior and their heritage features, which limit the range of suitable interventions. This study aimed to propose a range of suitable energy retrofit measures for Traditional Listed Dwellings (TLDs) in the South-East of England. It used representative case studies, selected in the city of Brighton and Hove, and devised a mixed-methods approach to model their energy performance and carbon emissions, before and after the application of interventions; the results obtained from dynamic energy simulation were assessed by means of parametric and sensitivity analysis. Providing an overview of the methodology adopted in the study, this paper presents the results of its first stage, aimed at addressing low-risk interventions. The discussion shows that the range of energy and carbon savings potential of the investigated measures is strictly intertwined with the range of baseline conditions of the dwellings investigated; the simulation of the retrofit interventions - individually and combined - highlighted the major effectiveness of draught-proofing amongst the low-risk retrofit measures for this part of the stock. The main novelty of this paper lays in the rigorous, layered, and systemic approach taken to assess low-risk energy retrofit solutions for TLDs by applying and testing them on multiple representative case studies.

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

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

A Systematic Analysis of Phase Change Material and Optically Advanced Roof Coatings Integration for Athenian Climatic Conditions

Energy retrofit solutions that concern a building’s roof structure play a significant role in the enhancement of a building’s thermal behaviour. This study investigates the integration of phase change materials (PCMs) with cool coatings (CCs) or thermochromic coatings (TCCs), namely, a PCM roof, a PCM-CC roof, and a PCM-TCC roof, as alternative and novel tactics for the simultaneous control of solar heat transfer and solar heat reflection. An energy simulation analysis with the DesignBuilder tool is conducted for a one-story residence and the climatic conditions of Athens. The simulation results indicate that, compared to the existing concrete roof construction, the PCM roof, PCM-CC, and PCM-TCC roof systems demonstrate energy savings that reach up to 13.55%, 16.04%, and 21.70%, respectively. The systematic analysis reveals that the increase in PCM’s thickness leads to an increase in the total electricity savings of the buildings, but in the case of PCM-CC and PCM-TCC roof systems, they merely effect the cooling thermal loads. The mean phase transition temperature that favours the cumulative electricity savings is 28 °C in the case of PCM and PCM-TCC roof systems and 35 °C in the case of PCM-CC roof systems. The methodology of this study allows the design of efficient, integrated roof systems with advanced thermal and optical properties as energy retrofit solutions for Mediterranean climatic conditions.

Energy performance assessment of a post-retrofit office building using measurement and verification protocol: A case study from KSA

Buildings account for over one third of the global energy consumption and greenhouse gas emissions. While new buildings are being sought to be more efficient, retrofitting of existing building is also critical to improve the energy and environmental sustainability of the building sector. Measurement and Verification (M&V) based energy retrofitting studies are becoming important in presenting the case for energy retrofit solutions. This work presents an energy performance assessment of a retrofitted office building using the International Performance Measurement and Verification Protocol (IPMVP) option B to conduct the M&V. The building, an office block with a built-up area of 7,500 m2, is in the Eastern Province of Saudi Arabia. The work carries out a detailed energy audit of the building to investigate the energy saving opportunities. Of the identified options, five energy efficiency measures (EEMs) are implemented. The energy performance of the building is also helped by the installation of a rooftop Photovoltaic (PV) system. The results indicate that retrofit measures helped reduce the Energy Use Index (EUI) from 458.9 kWh/m2/year to 361.4 kWh/m2/year. The economic analysis finds the compound payback period for the investments to be six years.

The Role of Uncertainty in Shaping Individual Preferences for Residential Energy Renovation Decisions

This article examines a crucial question that has been raised in recent years in both policy and economic literature: the role of uncertainty as a barrier to energy retrofit decisions. We develop a discrete choice experiment to elicit preferences for energy renovation measures. This methodologically innovative experiment design includes two insurance schemes covering potential sources of uncertainty as attributes of the energy retrofit alternatives. We use a mixed logit model to investigate the nature of systematic heterogeneity in household preferences for attributes of energy retrofit solutions. The article shows that uncertainties related to future energy pricing and retrofit quality are negatively perceived during energy-renova-tion decision making. This impact varies according to household characteristics such as risk aversion and perceptions of the economic context. The results suggest that public policies should support and accompany the development of insurance schemes to increase energy renovation rates.

A new decision guidance tool for the adoption of energy retrofit solutions in historic buildings

Energy retrofit of historic buildings often represents a challenge for owners and practitioners due to the lack of knowledge and access to suitable solutions. The growth of awareness and interest in sustainability has caused an increase in the number of solutions available for improvement of historic buildings’ energy performance. What it is still missing is their dissemination across the involved stakeholders. This will improve practitioners’ trust on these solutions and the adoption by owners in the building renovation. In the framework of IEA SHC Task 59 and the Interreg project ATLAS, experts have collected well established and innovative solutions for historic building renovation presented in an online decision guidance tool. The set of solutions is structured in four groups: wall insulation, window solutions, solar systems and HVAC systems. For each group a decision tree was developed to guide the end-user with questions to the appropriate solutions for their building. The tool aims to inspire and motivate technicians and owners with a large number of possible solutions, which serve as a basis for further investigation and planning. With more than 130 documented solutions it is already a comprehensive tool that can be used as basis and extended in future.

Using hygrothermal simulations to define safe and robust energy retrofit solutions: interior insulation of a mountain hut with extreme climate conditions

Interior insulation is a crucial retrofit measure to improve the energy performance of historical building while preserving their exterior appearance. However, it affects the hygrothermal behaviour of the wall and for this reason it must be planned with a very detailed and careful approach. This becomes even more important when dealing with buildings that are subject to extreme climate conditions such as mountain huts. They are typically exposed to very cold temperatures for all year and to an elevated driving rain load. This paper presents the methodology followed to design the interior insulation intervention of a mountain hut located in Trentino-Alto Adige (Italy). The methodology is centred around the use of hygrothermal dynamical simulations at component level, but several other tools are used to identify the right input for these simulations: the analysis of monitoring data of nearby weather stations to define the exterior climate, simulations at the building level to calculate the interior climate and laboratory measurements to identify the correct material properties.

Assessing cooling energy reduction potentials by retrofitting traditional cavity walls into passively ventilated cavity walls

A major roadblock in achieving substantial building energy reduction is the low performance of old buildings that account for a significant portion of the building energy consumption. Finding low-cost energy retrofit solutions that do not disrupt occupants’ daily life during the retrofitting is the key to successful building energy retrofit initiatives. In this paper, a novel and low-cost exterior wall retrofitting solution is introduced, and its performance in reducing space cooling load was quantitatively evaluated to demonstrate its feasibility and effectiveness. The primary goal of this paper is to provide a quantitative assessment of the cooling-energy savings potential by using the proposed new wall system. The intended retrofitting targets are the large amount of existing cavity-wall buildings located in hot climate regions. The quantification of the before-after heat-flux reduction was conducted through a 3-dimensional steady-state low turbulence computational fluid dynamics (CFD) model, which is validated by benchmarking its prediction against the published experimental case results. The outcomes of the investigation suggest that this simple low-cost solution has great potentials in reducing buildings’ summer cooling load in hot climate regions. The applicability of this solution is not limited to retrofitting existing buildings. New energy-efficient building designs can also adopt this solution in their envelope systems.

Impact of passive architectural design strategies on the energy efficiency label in Argentina

This work proposes making a comparative analysis between the Energy Supply Index (IPE, in Spanish), defined by the National Housing Labeling Program based on the IRAM 11900 Standard, and the Passive Architectural Design Strategies (EPDA, in Spanish) defined in said standard. The comparison is applied to energy retrofit solutions for the evaluation of the improvements in Energy Efficiency (EE) in a dwelling in San Miguel de Tucuman, Argentina. Its goal is to evaluate the incidence of EPDAs on the IPE value of the dwelling. An assessment is made regarding their importance as a starting point for achieving a more comfortable, more energy efficient and sustainable architecture. It is concluded that passive strategies do not have a numerically substantial influence on the IPE, that determines the energy efficiency label of residential units in Argentina.

Towards a model for circular renovation of the existing building stock: a preliminary study on the potential for CO2 reduction of bio-based insulation materials

In the context of strategies for mitigating the impacts of climate change within European cities, increasing attention is being paid worldwide to the use of urban green infrastructure which, in addition to the potential for improving the quality of the urban environment, allow significant amounts of CO2 to be removed from the air. However, considering the peculiarities of the dense European cities, most of the available surfaces in urban areas are the perimeter walls of buildings of considerable age that are in urgent need of measures to upgrade their energy performance. Based on this premise, this paper investigates the potential for CO2 storage resulting from the application of energy retrofit solutions using biogenic insulating materials. Starting from the analysis of the demand for insulation materials necessary for the energy requalification of the residential existing building stock in 28 European countries, following the renovation target fixed by EU, the research analyses, through the adoption of a dynamic LCA approach, the environmental benefits of bio-based materials compared to traditional solutions. The use of these materials, especially if they are fast-growing - as the study shows - offers several advantages in terms of climate change mitigation by reducing the energy needs and CO2 emissions of the existing building stock and increasing carbon storage capacity within cities. The results of this study are intended to provide a robust database on which to build a model of circular building renovation that takes into account the environmental long-term effects of measures for increasing energy efficiency of buildings.

A Parametric Study and Performance Evaluation of Energy Retrofit Solutions for Buildings Located in the Hot-Humid Climate of Paraguay—Sensitivity Analysis

Nowadays, awareness concerning the need to use energy efficiently is increasing significantly worldwide, thus, improving the energy efficiency levels in the building sector has acquired high importance because of their energy saving potential. However, several intervention options are available to achieve high energy efficiency levels in buildings, and the choice must be made considering the efficiency of the solution and the costs involved. Considering this, the present research aimed to develop a parametric study of several energy retrofit solutions for buildings located in the hot-humid climate of Paraguay, in order to analyse their efficiency in terms of comfort rates and cooling energy needs. Furthermore, the Analytic Hierarchy Process (AHP) is employed as a decision-making method to choose the most suitable intervention considering the investment costs required. Thus, threshold values of thermal transmittance for the building thermal envelope components are established through a parametric study and sensitivity analysis of the simulations results. Considering that Paraguay does not have national building energy codes, the outcomes of this research will constitute a support and contribute for the thermal parameters regulation of buildings aiding to improve the energy efficiency of Paraguayan buildings.

Energy efficiency and economic analysis of retrofit measures for single-family residential buildings

The research elaborates various solutions using detailed economic evaluation and energy efficiency calculation and simulation technology for formulating applicable, energy and cost-efficient retrofit solutions of single-family residential buildings located in temperate climate areas. Primarily the annual energy demand for a reference existing single-family residential building was determined. The economic analysis was performed for six formulated refurbishment scenarios in order to determine which of the scenarios will demonstrate optimal performance both in energy and cost efficiency. A feasibility study was performed for the most efficient scenario, which included an economic evaluation of low temperature radiant heating systems were three energy suppliers (oil, natural gas and electricity for air to water heat pump) were compared. According to financial analyses the optimal scenario includes the replacement of windows, installation of 15 cm expanded polystyrene thermal insulation, low temperature radiant floor heating, with a payback period of ten years.

Energy retrofit solutions for heritage buildings located in hot-humid climates

Nowadays, increasing buildings’ energy efficiency represents an opportunity to improve their thermal performance and adapting them to the global warming effects. However, finding the most suitable intervention for heritage buildings represents a challenge since the best energy retrofit solution has also to achieve the preservation of the building’s original characteristics. This work seeks to evaluate the thermal performance of a dwelling located in the Historic Centre of Asunción. Subsequently, several retrofitting solutions for the building envelope were assessed to determine the most efficient solution for the building and climate under analysis. As results, energy-efficient solutions guaranteeing optimal conditions of habitability are proposed.

Resilience of robust cost-optimal energy retrofit of buildings to global warming: A multi-stage, multi-objective approach

The climate evolution towards a progressive increase of Earth's temperature is leading to many worrying consequences, involving different aspects of World life. Among them, a specific focus should be given to the resilience of building energy design to global warming, since the efficiency and effectiveness of energy conservation measures over time can be highly affected by climate change. In this vein, the paper applies a multi-stage, multi-objective approach to find robust cost-optimal energy retrofit solutions and to assess their resilience to global warming. The approach combines the software EnergyPlus and MATLAB® to implement an optimization genetic algorithm and a smart research strategy. This framework allows to explore a huge solution domain by investigating sundry performance indicators, such as energy needs, polluting emissions and global costs, thereby ensuring a robust assessment of cost-optimality. Different cost-optimal retrofit solutions are found for different global warming and economic scenarios. Finally, a careful decision-making is performed to identify a recommended solution that provides the highest resilience to the cited scenarios, yielding the best trade-off among energy, environmental and economic performances. The approach is applied to a typical Mediterranean building, located in South Italy. The recommended solution includes the energy retrofit of the whole building envelope and the replacement of energy systems. It requires an investment around 100€/m2 and, in most scenarios, produces high potential benefits in terms of primary energy savings (42÷44kWh/m2a), polluting emission reductions (11.5÷12.0kgCO2-eq/m2a) and global cost savings (5÷78€/m2).

A Multi-Step Approach to Assess the Lifecycle Economic Impact of Seismic Risk on Optimal Energy Retrofit

Most European buildings built before 1980s were constructed without any design concern for energy efficiency and environmental sustainability. In addition to this issue, over the last decades, the essential need of safer buildings has progressively attracted the interest of scientific community and government institutions. However, the strong interaction between energy and structural aspects in building retrofit design has never been handled via robust and reliable approaches. The present study explores this knowledge gap by introducing a novel multi-step approach that addresses the retrofit of existing buildings by integrating energy, structural and economic aspects. To this end, a multi-stage energy optimization is carried out by implementing a genetic algorithm and a smart research strategy. Thus, the cost-optimal energy retrofit solution is identified and the impact of the expected economic losses due to seismic damage is assessed throughout the building lifecycle. The methodology is applied to a multi-story residential building, considering the effects of two different building locations, namely Milan and Norcia. These latter are characterized by similar climatic conditions but by a different level of seismic risk, which is higher for Norcia. The outcomes show that the estimated seismic economic losses associated with the energy retrofit solutions are strongly affected by the building location. Thus, the selection of the optimal energy retrofit measures should be related to the building structural behavior in order to achieve reliable economic and sustainability benefits.

CASA, cost-optimal analysis by multi-objective optimisation and artificial neural networks: A new framework for the robust assessment of cost-optimal energy retrofit, feasible for any building

The cost-optimal analysis provides the most cost-effective energy retrofit solutions. This can strongly support the deep renovation of buildings. However, an outstanding question arises: How to achieve the robust assessment of cost-optimal solutions, feasible for any building? The paper answers this question by proposing a new multi-stage framework for cost-optimal analysis by multi-objective optimisation and artificial neural networks, called CASA. It couples EnergyPlus and MATLAB®. A genetic algorithm allows to select recommended retrofit packages by minimizing energy consumption and thermal discomfort. Among these packages, the cost-optimal solution is identified. It is robust because the algorithm explores a wide domain of retrofit scenarios. The optimization procedure uses artificial neural networks to predict building performance. Large-scale uncertainty and sensitivity analyses are conducted to support the generation of the networks. These latter are tested against data provided by current literature with excellent results. The networks’ applicability to whole building categories and rapidity of evaluation make the procedure feasible for any building. For demonstration, CASA is applied to a reference office building located in South Italy, by investigating the related category. The achieved cost-optimal solution produces global cost savings around 42.4€/m2, and significant reductions of energy consumption, discomfort hours and polluting emissions.

A Simple Method for the Comparison of Bioclimatic Design Strategies Based on Dynamic Indoor Thermal Comfort Assessment for School Buildings

Bioclimatic design strategies have been proposed for decades, on a qualitative basis, because a quantitative approach, ineludibly based on dynamic measurements or simulations, was too expansive and complex. If simulation considerably evolved, in the last years, in terms of speed, cost and diffusion of available tools, their utilization is still complicated by the managing a huge amount of hourly data. The passive behavior of a building, moreover, is not effortlessly synthetized: conditioned buildings may be easily compared just summing the hourly consumption of primary energy, while buildings with no thermal plant need more sophisticated statistical analyses because in these kind of buildings, it is particularly difficult to assess the effect thermal inertia. The existing school buildings stock has a strong need of energy renovation in accordance with Government vision of a community 24hours a day use and consequently increasing the requirement of comfort conditions and energy consumption. Hence, a current school building heated and not cooled is considered as application field of the novel methodology and a classroom is used to test different energy retrofit solutions compared against a base-line, in terms of capacity to decrease the indoor air temperature variation. The analyzed simulations have been thus compared with ideal comfort conditions by an original analysis approach based on a visual tool as a support for designers in choices comparison to simply assess and visualize the performance of building technologies.

Multi-criteria assessment for the effective decision management in residential energy retrofitting

Building sector is responsible for 40% of European energy consumption, of which heating and cooling account for around 70%. Moreover, 75% of buildings for 2050 are already built in Europe. On the road to a sustainable energy transition, this article develops a multi-criteria assessment methodology for the environmental, economic and social evaluation of different residential energy retrofit solutions, based on effectiveness indices. This methodology allows improving the decision management in residential energy retrofitting by identifying the most effective solutions according to the requirements and needs of each intervening agent (citizens, public administrations and private promoters). The methodology is based on the integrated analysis of environmental, economic and social variables. It is applied to a Mediterranean case study from Southern Spain built in 1955. As part of methodology, survey data from the different stakeholders were collected, identifying the keys that condition the viability of the measures. The results show that measures with few inconveniences to tenants, investment costs below 2000 ⿬/dwelling and payback periods below 15 years are the most viable by end-users⿿ implementation in the Mediterranean area, but between them, only efficient heat pumps allow achieving more than 45% of CO2 emissions reduction (with a payback period of 6 years).

Multi-stage and multi-objective optimization for energy retrofitting a developed hospital reference building: A new approach to assess cost-optimality

The ‘Energy Performance of Buildings Directive’ Recast (i.e., 2010/31/EU) establishes that building energy retrofit should pursue “cost-optimal levels”. However, a reliable and rigorous cost-optimal analysis is an arduous and computationally-expensive issue, especially for complex buildings such as hospitals. The paper tackles this issue by providing a novel methodology to identify robust cost-optimal energy retrofit solutions. Multi-stage and multi-objective (Pareto) optimization is performed with the aim of minimizing the computational burden required to achieve reliable outcomes. The methodology combines EnergyPlus and MATLAB® and includes two optimization stages, preceded by a preliminary energy investigation that performs Latin hypercube sampling and sensitivity analysis. The preliminary investigation and the first optimization stage, which runs a genetic algorithm, aim at detecting efficient energy retrofit measures (ERMs) to reduce thermal energy demand for space heating and cooling. In the second optimization stage, these ERMs are combined with further ERMs, addressed to improve the efficiency of energy systems and to exploit renewable energy sources. Investment cost, primary energy consumption and global cost related to the resulting retrofit packages are investigated by means of smart exhaustive sampling. Finally, the cost-optimal solution is identified both in presence of a limitless economic availability and of limited budgets. The methodology is applied to a hospital reference building (RB), which represents hospitals built in South Italy between 1991 and 2005. The RB is defined by using an original approach, as required by the complexity of the examined building category. The achieved cost-optimal retrofit packages imply a reduction of primary energy consumption up to 67.9kWh/m2a (12.2%) and of global cost up to 2932k€ (24.5%) with a maximum investment of 1236k€.