Passive Retrofit Research Articles

Energy saving and carbon reduction of the application of phase change materials in rammed earth heritage buildings

ABSTRACT The combination of conventional thermal insulation materials and phase change materials (PCMs) was proposed without damaging the appearance of REHBs, the internal insulation measures of four types of expanded polystyrene (EPS) and six kinds of PCM boards combinations were investigated, and 19 retrofit cases were obtained. By conducting detailed simulations of energy consumption and indoor temperature for different cases at different locations, and comprehensively comparing multi-objects (energy-saving, economic and low-carbon), the energy consumption, cost recovery period and carbon reduction of these cases are compared and analyzed. The results show that Case I (only EPS) has the best energy-saving performance, economy and carbon emission reduction, Case III (EPS and PCM) is the second and Case II (only PCM) is the worst. The energy-saving rate of Case I and Case III (16 ℃) differs by 5.65%, while the cost, incremental benefit and payback period differ by 9.34%, 10.2%, and 1.57 years, respectively. Case III is a new and better passive retrofit measure of the REHB. Its energy-saving, cost and carbon reduction are only about 10% lower than that of Case I, but it has better indoor comfort. The outcomes can provide a reference for the innovative energy-saving retrofit cases for REHBs.

Evaluation of passive cooling through natural ventilation strategies in historic residential buildings using CFD simulations

Natural ventilation in hot climates has the potential to save energy by reducing the need to use mechanical systems. Particularly in historic buildings, it should be considered as a passive retrofit strategy before the addition of any mechanical systems to accommodate their unique indoor environmental characteristics and ensure their preservation. This study investigates the efficiency of multiple natural ventilation strategies in cooling a historic residential structure located in San Antonio, Texas, USA, a hot and humid climate area. It also analyzes their potential to provide a thermally comfortable indoor environment during the spring and summer. Onsite data and ASHRAE standards were used to create and validate Computational Fluid Dynamics (CFD) and energy models. Six different natural ventilation approaches were simulated, and the results were analyzed and compared. The analysis revealed that all the considered scenarios can contribute to energy savings in both seasons, especially in spring, with cross ventilation being the most efficient strategy. It also proved that the size of the openings has an impact on thermal comfort. This study demonstrated that historic preservation and thermal comfort goals can be achieved simultaneously, and the results can be replicated in multiple historic structures in similar climate regions around the globe.

Double-Skin Facades for Thermal Comfort and Energy Efficiency in Mediterranean Climate Buildings: Rehabilitating Vulnerable Neighbourhoods

The ongoing global energy crisis in Europe has intensified energy poverty in vulnerable households, prompting a critical examination of passive retrofit strategies for improving the habitability of obsolete social housing in southern Europe from the 1960s. Given the Mediterranean climate’s characteristics (hot summers and mild winters), these buildings possess low thermal resistance envelopes designed for heat dissipation in summer but contribute to elevated heating demands in colder months. In response to the pressing need for solutions that strike a balance between reducing energy demand and ensuring year-round comfort, this research explores diverse approaches. Drawing insights from built prototypes in Colombia and Hungary and utilizing a validated simulation model in Seville, Spain, this study investigates the feasibility of implementing a double-skin envelope on building facades and assesses the impact of thermal insulation in the air chamber. So, the research specifically aims to find an equilibrium between lowering energy demand and maintaining adequate comfort conditions, concentrating on the renovation of obsolete social housing with envelopes featuring low thermal resistance in the Mediterranean climate. Results indicate that, due to the poor thermal envelope, the influence of thermal insulation on comfort conditions and energy savings outweighs that of the double skin. Consequently, the emphasis of renovation projects for this climate should not solely concentrate on passive cooling strategies but should strive to achieve a positive balance in comfort conditions throughout the year, encompassing both warm and cold months.

The TEnSE approach to assess the nudge of stakeholders in the choice of thermal insulation materials

The buildings’ energy efficiency and the energy poverty can be improved through the implementation of active and/or passive retrofit solutions. The thermal insulation of building envelope is one of the most employed retrofit solutions. Several thermal insulation materials are currently available in the building market. However, the choice of a specific material can depend on an ensemble of requirements ascribed to four domains – Technical (T), Environmental (En), Safety (S) and Economic (E). The TEnSE approach is here proposed to investigate the influence of specific stakeholders or nudgers in the selection of thermal insulation materials for building retrofit. It is a three-step approach, that starts from a) the identification of a set of alternatives and decision criteria, b) the assignation of parameters and their normalization, and c) the definition of a weights’ matrix and calculation of the Stakeholders’ Score. As an example, here, the TEnSE is used to study the influence of stakeholders in the choice of the most used thermal insulation materials in three countries of the European Economic Area. The TEnSE approach can be used beyond a products’ score tool, as experts in social sciences and climate/energy policies could depict what are the decisional patterns of public, private, and people to enhance the green awareness and fill the legislative and political gap towards this topic.

Evaluation of suitability for passive retrofit of wooden roof considering the specificity of historic buildings

Energy consumption and carbon emissions of buildings must be reduced according to the 2030 carbon neutrality policy. Many aspects of historic buildings should be considered in their improvement because of their historical value. Thus far, a new strategy to lower energy consumption and improve energy performance is required. This study intends to derive an optimal energy efficiency package to reduce the energy consumption of historic buildings. To accurately analyze energy efficiency, the condition of a historic building was evaluated through on-site inspections. The roof retrofit technology scenario was used to reduce energy loss in exposed rafters. The exterior of the building cannot be damaged as it has historical value. This retrofit technology was analyzed to determine the energy-saving effect and economic feasibility of the package to derive the optimal solution. Retrofit techniques were individually analyzed and packaged for the effective preservation of historic buildings. This study compared a total of six scenarios by combining three types of insulation materials, based on the location of internal insulation, to protect the exposed rafters. Considering energy-saving, economic feasibility, and damage weight, the scenario where polyurethane insulation was applied between battens was the best. However, the insulation of the roof must consider fire resistance as per the Building Act of the Republic of Korea. Considering flame-retardancy, the scenario in which glass wool was applied between batten was the best for the target building.

A French Residential Retrofit toward Achieving Net-Zero Energy Target in a Mediterranean Climate

Cities are paying more attention to building energy use and carbon footprint for attaining sustainability. Within this building sector, there is a growing attention toward development and adoption of energy efficient retrofit strategies. Plagued by the lack of efforts in achieving comprehensive energy efficient retrofit solution sets (passive, active, and renewable energy systems), the authors acknowledge the concept of NZEB toward achieving energy efficiency by 2050. Toward this end, a numerical energy simulation modeling is carried out to retrofit an existing French “Puccini house” using ‘passive, energy efficient building systems and renewable energy’ strategies toward an NZEB target in the Mediterranean climate of Nice. Using Design builder 7.0, the simulated baseline energy model (Case A) is retrofitted through variations in the proposed energy efficient retrofit measures using two case scenarios (Case B: passive retrofit; Case C: energy-efficient building) to achieve NZEB (Case D). Assessing the performance of energy efficient retrofits using % energy reduction, the implementation of a high-performance building envelope is achieved using a thermally insulated external wall (46.82%), upgraded airtightness (20.39%), thermally insulated pitched roof component (33.03%), and high-performance window type—a glazing system (3.35%) with maximized window-to-wall ratio (5.53%). The maximum energy-saving retrofit solutions provide an ambitious reduction in energy consumption by approximately 90% from the baseline. A deep retrofitting of the French house meets the NZEB targets, as it reduces the baseline energy consumption from 194.37 kWh/m2/year to 23.98 kWh/m2/year using both passive and active strategies. The remaining energy demand is met by the integration of on-site PV panels (EUI= −27.71 kWh/m2/year), which achieve an increase in energy production by 15.5%, while returning energy back to the grid (−3.73 kWh/m2/year). Findings of this study serve as a guideline for retrofitting traditional French single-family residences, while contributing toward the NZEB goal.

Retrofitting Historic Buildings for Future Climatic Conditions and Consequences in Terms of Artifacts Conservation Using Hygrothermal Building Simulation

Climate change will greatly influence the world at several levels and will have consequences on the interior climate of historic buildings and artifacts conservation. Buildings are responsible for a large slice of the overall emissions, which is due both to the greenhouse gases that are released during their construction as well as the activities that are performed therewithin. One way of counteracting this trend is to design more efficient retrofit buildings and predict their behavior using simulation software, which can thoroughly assess the performance of new buildings or the impact of each retrofit measure for existing buildings. In this study, a calibrated computational model of high thermal inertia building was used to assess the performance of passive retrofits in mitigating the effects of climate change concerning artifact decay mechanisms. In addition, a methodology that aims to reduce the amount of time spent to perform these studies is also presented, in which time savings reach up to 63%.

Historic building energy conservation with wooden attic using vacuum insulation panel retrofit technology

The envelopes in historic buildings must be preserved as aging historic buildings continue to be used. Conservation is necessary to improve the energy performance of historic buildings. The target building of this study has an exposed rafter structure. Modern historical buildings in Korea do not have a passive retrofit, which is insulation. The passive retrofit covering the roof structure needs to be applied taking into account the original protection of the exposed rafters. This study aims to examine the energy improvement effect of a historic building with a roof with an exposed rafter structure. Considering the characteristics of the building, a vacuum insulation panel (VIP) retrofit technology is used instead of general insulation. The VIP is thin and has high heat resistance, so there is little damage to the envelope of historic buildings, and the U-value of the existing roof layer is reduced by 88%. By applying retrofitting technology, the annual energy consumption of the top floor was improved by 55%. Cooling on the top floor showed an improvement of 29.87%. The largest energy savings occurred in May at 49%. This is because the VIP retrofit technology is applied in the form of external insulation. External insulation lowers heat storage owing to solar radiation. The developed VIP was suitable for Korea's preservation considerations and building energy conservation considerations.

Energy-saving and thermal comfort potential of vernacular urban block porosity shading

Built environment configurations of vernacular architecture are the result of an evolutionary adaptation to climatic conditions, while the historic districts of many cities worldwide are shaped by their extensive architectural heritage. These factors, coupled with the present day awareness and renewed interest in the passive retrofitting of buildings, have prompted a review of traditional strategies, most notably direct solar radiation management through courtyard perforations. Although the vernacular courtyard microclimate has been discussed in the literature in recent years, few studies have successfully translated its climatic benefits to the city scale in order to assess its real potential. There is a notable absence of overall urban estimations of the impact on energy-saving and thermal comfort of some of the most effective strategies, such as the use of shading devices. Combining state-of-the-art GIS-based tools and statistical data analysis from field monitoring campaigns this research performs a large-scale evaluation in urban courtyards in the historic centre of a Mediterranean city. Based on the results obtained it can be stated that a widespread use of shading devices can increase the number of hours of comfort, according to PET, by 27% and can reduce global cooling demand by 31%.

Evaluation of environmental comfort in a social housing prototype with bioclimatic double-skin in a tropical climate

The aim of this paper is to broaden understanding of the social housing prototype that students and researchers at the University of Seville developed in response to tropical climate conditions to achieve the maximum level of hygrothermal comfort through the use of passive retrofit strategies.This prototype, known as Aura 1.0, was presented at the Solar Decathlon competition where hygrothermal conditions inside the prototype were monitored over a ten-day period. Nevertheless, as the monitoring period of the environmental conditions was so reduced, the aim of this research is to assess the environmental behaviour of the prototype for a full year, under tropical climate conditions. To do so, energy and environmental simulation instruments will evaluate the performance of the architectural proposal and its passive construction systems, in particular the double skin designed with different objectives (architectural, construction, socio-economic).The simulation model has been verified by the data monitored during the exhibition phase and the performance of the building. Various hypotheses have been analysed which demonstrate that employing a double skin in the dwelling contributed to improving interior thermal comfort, especially in the roof area as opposed to the facades, given the sun's path at a latitude close to the equator.

Fighting energy poverty in a typical Peruvian rural house

This study evaluates a typical, informal construction in the Peruvian highlands of Cuzco, a site at an Equatorial latitude (13,5° S), approximately, 3.400 mamsl, with a subtropical highland climate (Köppen Cwb). Its aim is to compare low-cost passive retrofit strategies, applicable in cities and rural areas with similar climate, and validate a best choice. To carry out this study a dynamic energy simulation was performed, using the typical meteorological year (IWEC) provided by ASHRAE. The model was used to understand the effects of simple changes in the envelope configuration and the associated effect on infiltration, and their combination, on the indoor comfort and the energy performance of the building. The outcomes were displayed in a simple Energy-needs/transformation cost chart and a Pareto curve was selected, identifying an optimal subset of solutions. Adequate indoor conditions can be obtained with the implementation of only passive strategies, mainly empowering the thermal insulation of walls, roofs and windows using simple, low cost, local technologies, and the control of the heat transmission toward the soil: the energy poverty of the informal settlements of Cuzco can be fought with very simple initiatives, that require investments with a reasonably short return of investment.

Improving the Passive Energy Performance of the Buildings’ Envelope in the Southern European Area: A Study on the Integration of a Tensile Material

In this paper, the energy and environmental impacts of a passive retrofit action, involving the installation, on an office building, of a second-skin system with the external layer made of a PVC-coated polyester fabric, were evaluated in terms of primary energy saving and carbon dioxide equivalent emissions. The primary energy consumption and the carbon dioxide equivalent emissions associated with the considered case studies were evaluated through the dynamic simulation software TRNSYS, across a whole year. The study was carried out considering five cities (Athens, Barcelona, Lisbon, Marseille and Naples) in five different countries in southern Europe upon varying the orientation of the two main façades of building (north-south and east-west orientation were considered). The office building was modeled in detail considering different construction characteristics upon varying the country. The simulation results highlight that the best results in terms of PES (equal to 22.4%) in Naples, while the best results in terms of CO2 (equal to 32.0 MgCO2,eq) were obtained when the building is located in Athens. In addition, the adoption of the proposed passive lightweight retrofit solution allowed the reduction of both cooling and thermal yearly energy demand up to 57.7% (Marseille) and 17.8% (Barcelona), respectively.

Assessment of Passive Retrofitting Scenarios in Heritage Residential Buildings in Hot, Dry Climates

Retrofitting heritage buildings for energy efficiency is not always easy where cultural values are highly concerned, which requires an integrated approach. This paper aims to assess the potential of applying passive retrofitting scenarios to enhance indoor thermal comfort of heritage buildings in North Africa, as a hot climate, a little attention has been paid to retrofit built heritage in that climate. A mixed-mode ventilation residential building in Cairo, Egypt, was selected as a case study. The study combines field measurements and observations with energy simulations. A simulation model was created and calibrated on the basis of monitored data in the reference building, and the thermal comfort range was evaluated. Sets of passive retrofitting scenarios were proposed. The results (based on the ASHRAE-55-2020 adaptive comfort model at 90% acceptability limits) showed that the annual thermal comfort in the reference building is very low, i.e., 31.4%. The application of hybrid passive retrofitting scenarios significantly impacts indoor thermal comfort in the reference building, where annual comfort hours of up to 66% can be achieved. The originality of this work lies in identifying the most effective energy measures to improve indoor thermal comfort that are optimal from a conservation point of view. The findings contribute to set a comprehensive retrofitting tool that avoids potential risks for the conservation of residential heritage buildings in hot climates.

Performance of passive retrofit measures for historic buildings that house artefacts viable for future conditions

Retrofitting a building normally aims to achieve a higher quality indoor climate in terms of thermal comfort or in terms of air quality, as well as reducing the building’s energy consumption. Alternatively, in buildings that house artefacts, the application of retrofit measures normally aims to improve the indoor climate in terms of the artefacts’ conservation. However, the outdoor climate, which greatly influences the indoor climate of buildings, is changing significantly. Hence, it is obvious that when retrofitting a building it is of key importance to consider this change, especially in historic buildings that house high-valued artefacts.This paper aims to study the performance of several types of retrofit measures in historic buildings that house artefacts by considering climate change. A validated hygrothermal model of a 13th-century church was used coupled with future weather files and a risk-assessment methodology based on damage functions.It was found that passive retrofit measures can mitigate some of the negative impacts that climate change is expected to induce in historic buildings that house artefacts. However, these measures can also lead to the decrease of the conservation metrics. Consequently, ranges of thicknesses of the analysed retrofit measures that ensure the conservation metrics are presented.

Educational building retrofit under climate change and urban heat island effect

Climate change (CC) and urban heat island (UHI) are important environmental forces that have serious consequences for the existing buildings, such as increased resource consumption and environmental footprint, adverse human health effects and reduced occupant comfort. In this context, educational buildings represent a critical category amongst other building typologies, due to their high energy use, high occupant density, atypical daily/annual occupancy patterns, and their occupants’ high vulnerability to heat. Poor indoor conditions can reduce the health and productivity of students and teachers, worsen learning performance and reduce attendance. Retrofitting educational buildings is an effective solution to tackle this challenge. This study investigates the impact of CC&UHI on educational building performance and demonstrates the effectiveness of passive retrofit scenarios targeting CC&UHI mitigation and adaptation. These investigations are based on a systematic approach that consists of (i) the generation and analyses of CC&UHI-modified weather datasets, and (ii) simulation-based comparative analyses of the as-is building and various retrofit scenarios. An existing secondary school building in Ankara, Turkey is selected as a case study for evaluations of the selected performance indicators including energy use, global warming potential (GWP) and thermal comfort. Obtained results indicate that total energy consumption can be reduced up to 50% with retrofit, whereas possible reductions in indoor discomfort are even more pronounced, underlining the significance of selecting the optimal combination of passive measures for maximum impact towards the adaptation of the existing educational buildings to the changes in climatic conditions.

Solar Bridge Retrofit System: An innovative solution to renovate structural thermal bridge areas

The structural components of load-bearing concrete frame buildings, such as concrete beams and columns, are critical elements of the facades which often act as a thermal bridge. To reduce the impact of structural thermal bridge areas in non-retrofitted Portuguese residential buildings, a new innovative solar passive retrofit solution, named Solar Bridge Retrofit System (SBRS), is proposed. This concept relies on the principles of unvented Trombe wall systems and consists in using an external transparent skin in front of the structural areas of the envelope in combination with the traditional ETICS in the remaining area. Contrary to the traditional Trombe walls, this innovative design enables the heavy structure of the building to absorb solar radiation and conduct the heat slowly inward or to the adjacent structure.To evaluate the thermal performance of the SBRS, an experimental setup was developed. The field results obtained during February and March 2020 for two different configurations, showed that the double-glazing configuration in combination with ETICS has the potential to improve thermal comfort and reduce energy consumption. This paper addresses both the design of the SBRS and the obtained results from the experimental work.

Comprehensive energy, economic and thermal comfort assessments for the passive energy retrofit of historical buildings - A case study of a late nineteenth-century Victorian house renovation in the UK

This paper aims to evaluate the energy-saving potential, affordability and thermal comfort performance of various passive building retrofit measures for a historical building (late nineteenth-century Victorian house) renovation. Three types of interior passive retrofit measures (i.e. internal wall insulation, glazing upgrade and airtightness improvement), classified as traditional and advanced measures, are further grouped into 63 retrofit combinations. In order to evaluate the performance of these defined retrofit combinations, five assessment indicators are proposed, including energy reduction rate, specific initial cost, discounted payback period, space volume reduction rate, and indoor thermal comfort. Under three internal space reduction scenarios with a space reduction rate of 5.2%, 2.6% and 1.3%, these combinations are evaluated and compared, and the most favourable combinations are determined to achieve multiple objectives (maximum energy saving, most cost-effective and most energy-efficient). The influence of the most favourable retrofit combinations on the internal thermal comfort level improvement is also dynamically evaluated using the EnergyPlus simulation tool. The final recommended passive retrofit combination consists of vacuum insulation windows, gypsum air infiltration reduction, and 2 cm thickness of Polyisocyanurate (PIR) panels, with 51.8% of primary energy reduction, a specific initial investment of £144.71/m2 and a discounted payback period of 18 years.

Internal thermal environment and futureproofing of a newly built, naturally ventilated UK school

Research indicates that school children have lower comfort levels than adults and this exacerbates the challenge of tackling the risks of summer overheating in schools without resorting to air conditioning. UN SDG 13 calls for climate action to strengthen the resilience of our cities and reduce the impact of climate change. In this work, a modern, naturally ventilated school in Southampton, UK was used to evaluate single, “hard”, passive retrofit measures and “soft”, building management solutions that could increase the wellbeing of students and reduce current and future demand for cooling. The school was selected as it represents the current standardised design guidance for schools released in 2012 by the Department of Education (DfE). The research presents air temperature observations collected during the summer of 2015. Dynamic thermal modelling was undertaken to evaluate passive retrofit and “soft” solutions to reduce the overheating risk. The model was validated with temperature data collected from the school classrooms. The results indicate that (a) such school buildings have high likelihood of overheating, based on children’s comfort temperatures and (b) passive retrofits focused on shading and ventilation could help to reduce the classroom temperature when required. It is recommended that “soft” adaptive solutions will prove effective to reduce future air conditioning demand, but this will require a radical change in established practices. Achieving the UN Sustainable Development Goals by 2030 will require to rethink and redesign urban living and city infrastructures.

Impact of climate change in cultural heritage: from energy consumption to artefacts’ conservation and building rehabilitation

Historic artefacts must be properly preserved if they are to be transmitted to future generations. Indeed, several methodologies and guidelines that aim to safeguard artefacts by limiting the ranges in which the indoor temperature and relative humidity vary exist, which means energy consumption. This paper aims to quantify the energy consumption associated to three different setpoints and respective financial cost, as well as their future trend to demonstrate the positive outcome of passive retrofit measures, since they will be responsible for decreasing the building’s energy consumption and mitigating the effects of climate change in artefacts’ preservation. A validated whole-building hygrothermal model of a historic building was used coupled to climate change weather files to obtain the expected future indoor conditions for three types of climates, which were also assessed using a risk-based analysis. The positive potential of passive retrofit measures on the building’s energy consumption was shown, but the risk-based analysis showed that the measures performance are not universal since, for example, whilst the selected measures decrease the risk of chemical decay for Seville, they have the contrary behaviour for Oslo. To achieve these goals more than 1400 simulations were run in WUFI®Plus, which took more than 1600 h.

Impact of a passive retrofit shading system on educational building to improve thermal comfort and energy consumption

To improve the energy performance of existing buildings, retrofits may improve the energy efficiency or decrease energy demand. Many studies have been conducted on passive retrofit systems using phase change materials (PCMs). In this study, the objective is to analyze the energy performance and thermal comfort of an educational building with a shading system in South Korea. When PCMs were applied to the shading system, the cooling energy consumption decreased by 44%, and the number of hours of thermal comfort improved by 34%. The melting temperature of the PCM did not play a significant role in reducing the building energy consumption when the PCM was applied to the shading system.In the economic aspect, although the PCM shading application requires more additional investment, the simple payback period (SPP) of the PCM shading application is lower than the building without PCM. Therefore, the PCM shading application to A Hall is a successful retrofit that has more energy efficiency and thermal comfort, and has a lower SPP. However, the increase in heating energy consumption due to the shading application in winter could not be overcome. This implies that further research on the shading system in cold climates are required.