Retrofit Materials Research Articles

Low-impact thermal insulation materials for sustainable retrofitting: potentialities and barriers from a literature review

Abstract The present study provides both an updated overview of the most recent studies about low environmental impact materials for building retrofitting and meta-analyses of the most important features, such as the thermal conductivity, allowing to evaluate their insulation potential against the diffused and recurrent conventional competitors. Specifically, 466 case studies about materials derived by co-production, wastes of other products and recycled ones have been selected and their thermal performances have been analysed. The materials have been clustered into homogeneous classes: lose materials and foams; structural materials; panels; finishing materials. The results show that some low environmental impact materials are characterized by thermal performances which can position them as materials able to contribute to building decarbonization, but little information can be found about other characteristics which can be crucial when the built environment is considered, such as durability, fire resistance, costs, and load resistance. Yet, these latter aspects may be investigated further when the material is considered to enter the prototyping phase whether in the academic or market context. The present study provides a base for discussion about the use of more environmentally friendly thermal insulation materials which in the coming years might represent a valid option for sustainable building renovation.

Retrofitting homes in Ontario entails significant embodied emissions: new policies needed

ABSTRACT Emissions reduction policies and programs should consider both the operational emissions reduction from single family home retrofits and the embodied emissions of the retrofit materials. This is because it can take 0.9–10.1 years before the emissions savings from building envelope upgrades in a gas-heated home equal the embodied emissions from the materials used. The wide range reflects the range of embodied emissions for different insulation and window replacement options. Heat pumps also have significant embodied emissions from their manufacture and from refrigerant leaks, but it takes less than two and a half years of operations in Ontario to offset the emissions investment relative to heating with a gas furnace. We recommend that Canada accelerate the phase out of insulation materials with high embodied emissions and increase incentives for window replacements. Programs and policies should also consider the age of the home and the potential energy savings when recommending building envelope improvements to maximize the total emission reduction potential. Finally, heat pumps should be promoted in all homes where low carbon electricity is available because this is the simplest and most effective way to reduce carbon emissions, especially when embodied emissions are considered.

Embodied impacts of key materials for UK decarbonised domestic retrofit: Differences between sources of embodied carbon and embodied energy data

Low energy domestic retrofit consumes materials, such as insulation, membranes and glazing, with smaller quantities of structural timber, steel or concrete, which have associated embodied impacts from resource extraction, manufacture and end-of-life treatments. In retrofit design, coefficients for material embodied impacts vary widely between sources and can lead to different results in a life cycle energy or carbon analysis, and perhaps different material choices in retrofit implementation. This paper considers how and why results differ between sources, and whether such data is suitable for making climate-beneficial design decisions. Embodied energy and carbon coefficients for 18 key retrofit materials were obtained from two widely used LCA databases and their similarity was quantified. The data collected illustrates that 70% embodied energy and embodied carbon data is within 20%, but that 30% of data was more than 20% different. Consistency of product naming and the absence in the datasets of key retrofit materials are factors identified contributing to variation, and present real constraints in practice. Furthermore, this exercise showed that embodied impacts for the types of materials most prominent in retrofits are less-well characterised than other major construction materials, and presents another layer of uncertainty. The data showed embodied energy was more consistent between sources than embodied carbon. This raises doubts about the predominant use of embodied carbon over energy for such analyses and establishes that a focus on embodied carbon over embodied energy has less power to reduce greenhouse gas emissions than considering both metrics together. It is concluded that obtaining such data with confidence is challenging and requires expertise in LCA, and is therefore unlikely to be accessible to most retrofit designers. Datasets need to be more complete and offer higher confidence to ensure delivery of high quality and meaningful results for climate-beneficial design decisions.

Effects of passive confinement on out-of-plane robustness of unreinforced masonry infill walls

Unreinforced masonry (URM) walls are vulnerable to out-of-plane (OOP) collapse under lateral loads; however, URM structures are still popular in developing countries. Even in many countries classified as developed by the United Nations, URM walls are still commonly applied as exterior and interior infills in engineered buildings, resulting in severe OOP failure during strong earthquakes. The objectives of this study were: 1) to experimentally examine the OOP behavior and performance of URM infills with construction deficiencies commonly found in Asian countries, 2) to investigate the impact of construction quality on resistance to OOP collapse and 3) to propose a promising approach using passive confinement to improve the lateral resistance of URM infills and a method to evaluate their seismic performance. To attain these objectives, the study used two full-scale, single wythe, brick masonry specimens with specific boundary conditions at the top, a control specimen representing URM infills with construction flaws frequently found in Asian countries and a well-constructed specimen subjected to passive confinement under lateral excitation. A series of incremental dynamic shaking table tests was performed on both specimens under OOP unidirectional one-way bending. The test results revealed the positive effects of construction with passive confinement on OOP performance. The results indicated that the OOP robustness of infills can be improved without specific retrofit materials, leading to advantages such as simplicity, cost-effectiveness, and swift execution. Moreover, a theoretical method to evaluate the lateral resistance of infills was presented and verified for practical applications. This method can contribute to reducing the potential for earthquake damage in engineered buildings.

Assessing the effectiveness of building retrofits in reducing GHG emissions: A Canadian school case study

This paper investigates the impact of energy retrofits on life cycle greenhouse gas (GHG) emissions across different electricity grid profiles in Montreal, Ottawa, and Halifax, using an existing school building as a case study. Using DesignBuilder for energy simulations and OneClick LCA for GHG emissions estimation, this study evaluates whether the reduction in the operational emission achieved by energy savings from retrofits can outweigh the increased embodied emissions from new envelope materials and equipment. In Montreal and Ottawa, where electricity is mainly generated from renewables and non-fossil fuels, retrofits involving electric heating and envelope improvements could decrease life cycle GHG emissions by up to 75 %. However, if the building initially used electric heating, the retrofits led to an increase in life cycle carbon emissions by 170 % in Montreal and 56 % in Ottawa, respectively, due to the embodied emissions of retrofit materials and equipment. In Halifax, where the electricity grid relies heavily on fossil fuels, all retrofit scenarios showed a positive impact on GHG reductions. Enhancing the building envelope and transitioning from natural gas to electric heating slightly reduced total emissions by 4 %, but retaining natural gas heating decreased the total life cycle GHG emissions by 27 %. This study emphasizes the importance of a comprehensive life cycle assessment in developing policies for achieving carbon neutrality. It demonstrates that the effectiveness of retrofits in reducing GHG emissions significantly depends on the local energy grid, suggesting tailored approaches based on regional energy profiles to optimize emission reductions and energy efficiency.

Green Structural Retrofitting Materials for Fire-Damaged Reinforced Concrete Buildings: Advances in Sustainable Repair of Distressed Buildings

Green Structural Retrofitting Materials for Fire-Damaged Reinforced Concrete Buildings: Advances in Sustainable Repair of Distressed Buildings

Evaluation Research on Energy-Saving Retrofitting of Roofs of Traditional Wood-Structured Dwellings Based on the Continuation of Historical Features: A Case Study of Guangdu Village No. 280 Dwelling in Zhejiang

China has numerous traditional wooden dwellings located in regions with hot summers and cold winters. The historic dwellings lack proper thermal insulation and have excessive energy consumption in the building structure, failing to suit the needs of modern people. Hence, it is crucial to enhance their energy efficiency through essential actions. Roofs, being the fifth side of the building envelope, are frequently neglected when it comes to enhancing their insulating capabilities. The study aimed to implement energy-efficient roof alterations while preserving the historical features of traditional structures. This study focuses on enhancing the energy efficiency of a traditional wood-structured dwelling in Guangdu Village, Zhejiang Province, China, by installing composite thermal insulation panels on the interior of the roof using an easy restoration approach. The actual risk of condensation and the impact of retrofit processes on historical features determine the choice and limitations of energy-saving retrofit materials and methods. This study evaluates the transformation using two indicators: energy efficiency and economic feasibility. The numerical simulation results indicate that traditional dwellings have an annual energy savings rate of 16.66% and an investment payback period of 7.25 years. This study demonstrates the feasibility of energy-saving roof renovation measures for these traditional wood-structured dwellings. The measures improve energy efficiency and are affordable for residents. This study can offer technical suggestions for enhancing the energy efficiency of traditional wood-structured dwellings.

Integrated Seismic and Energy Retrofitting of Masonry Elements Strengthened with PCM-enhanced GTRM/FRCM systems

The integration/combination of seismic and energy retrofit measures has been a subject of study for the past decade, exhibiting promising prospects. The main objective of these interventions is to mitigate seismic vulnerability while concurrently enhancing the energy performance and efficiency of new and existing buildings. Integrated approaches can hold the potential for substantial cost savings, time efficiency, and minimal disruption to occupants. The current body of literature emphasizes exploring the benefits of incorporating innovative methods/materials into conventional uncoupled retrofit initiatives. This study focuses on evaluating integrated measures at the panel scale for the prevalent Unreinforced Masonry (URM) typologies in Italy. A design framework has been introduced, aimed at enhancing the seismic capacity of buildings while concurrently improving energy efficiency through the integration of new materials (e.g., highly latent thermal energy storage systems achieved through the integration of Phase Change Materials - PCMs) into retrofit materials. To assess the reduction of the seismic vulnerability, the improvement of the shear strength is estimated by modifying the failure domains, while energy efficiency and thermal-energy storage enhancements are evaluated by using enthalpy-based theories, implemented into open-source software (i.e., FEM-based and through EnergyPlus). Thus, the design variables are those defined by the URM typologies, the adopted retrofitting technique, and the considered envelope. The adopted integrated (seismic and energy retrofitting) solutions will be compared with the standard reference one in terms of the energy consumed by the enclosed building to keep the indoor thermal comfort which also guarantees the target level of structural performance.

Experimental Study of Reinforced Concrete T-Beam Retrofitted with Ultra-High-Performance Concrete under Cyclic and Ultimate Flexural Loading.

Structurally deficient bridges are commonly retrofitted using conventional methodologies, including reinforced concrete, steel jackets, and fiber-reinforced polymers. Although these retrofit methods aim to improve structural performance, exposure to aggressive environments may undermine the durability performance of the retrofit material. More recently, ultra-high-performance concrete (UHPC) has provided an alternative to conventional construction methods, with its superior material characteristics favoring its use in retrofit applications. In this study, a large-scale reinforced concrete (RC) T-beam is constructed and artificially damaged. The T-beam is then retrofitted with an external envelope of UHPC on all faces. Sandblasting is introduced to the surface, providing partially exposed reinforcement in the T-beam to simulate material deterioration. Additional reinforcement is placed in the web and flange, followed by casting the enveloping layer of UHPC around the specimen. The feasibility of this method is discussed, and the structural performance of the beam is assessed by subjecting the beam to cyclic and ultimate flexural loading. This paper presents the results of cyclic and ultimate testing on the RC-UHPC composite T-beam regarding load-displacement, failure mode, and strain responses. The retrofitted T-beam specimen is subjected to a cyclic loading range of 131 kN for 1.576 million cycles. Despite no visible cracks in the cyclic testing, the specimen experiences a 12.22% degradation in stiffness. During the ultimate flexural testing, the specimen shows no relative slip between the two concretes, and the typical flexural failure mode is observed. By increasing the longitudinal reinforcement ratio in the web, the failure mode can shift from localized cracking, predominantly observed in the UHPC shell, toward a more distributed cracking pattern along the length of the beam, which is similar to conventional reinforced concrete beams.

Determining the Allowed Fiber Content for WHBR (Water Hyacinth and Bio-Resin) FRP Composite as the Future Environmentally Friendly External Concrete Retrofit Material

Determining the Allowed Fiber Content for WHBR (Water Hyacinth and Bio-Resin) FRP Composite as the Future Environmentally Friendly External Concrete Retrofit Material

EVALUATION OF RETROFIT EFFECTIVENESS AND COST IMPLICATIONS OF MRF STRUCTURES USING DISTINCT FRCM COMPOSITE SYSTEMS

This paper summarizes the results of a numerical investigation to assess the effectiveness of retrofitting pre-seismic code concrete framing structural systems using two distinct fiber-reinforced cementitious matrix (FRCM) composites. While FRCM composites were focused in the literature at the member level, this study focuses on implementing this retrofit technique effectively at the structure level. Several static pushover analyses (SPAs) and inelastic dynamic simulations (IDSs) are carried out for FRCM-retrofitted RC frames representing the lateral force-resisting system of a moment-resisting frame (MRF) structure. Correlating the numerical simulation results and experimental results obtained from another study verified the selected fiber discretized section modeling technique for FRCM retrofitted MRFs and reflected the effectiveness of the adopted approach in prolonging local and global damage states. The verified modeling technique of the risk-mitigation measure is then employed to evaluate the performance of an upgraded RC building using three-dimensional fiber-based numerical models. Finally, a parametric study using SPAs and IDSs using multiple seismic scenarios is conducted to select the most effective FRCM retrofit material for the seismic performance enhancement of the benchmark structure. The study concludes that using the selected FRCM retrofit technique effectively mitigated the structural collapse damage state of the substandard building at the design and maximum considered seismic intensity levels by 28% and 32%, respectively.

Deep energy retrofits using different retrofit materials under different scenarios: Life cycle cost and primary energy implications

Deep energy retrofits of existing buildings can contribute to achieving a renewable-based society, though they are mostly lacking in the EU. To understand the cost and primary energy savings of deep energy retrofits, all life cycle phases, including construction, operation, maintenance and end-of-life, must be considered. The initial building without retrofit must be analysed over its remaining lifetime covering energy operation, maintenance and end-of-life implications that change with a retrofit. Such a method is applied to a multifamily building retrofitted to two passive house standards limiting annual final heat use to 50 and 30 kWh/m2. Energy improvements to the building envelope are analysed considering different versions of initial cladding materials and retrofit materials, and different economic and electricity supply scenarios. A retrofit to 50 kWh/m2 is profitable for all economic scenarios while the 30 kWh/m2 version is profitable for most of the scenarios giving net primary energy savings of 57–60% and 63–72%, respectively, compared to the non-retrofitted building. The cost of different retrofit materials is similar, while the primary energy use is much lower for wood-based materials. The changed costs and primary energy use for the non-retrofit building, in maintenance and end-of-life phases, varies depending on assumed initial cladding materials.

Green engineered mulch for phosphorus and metal removal from stormwater runoff in bioretention systems

Phosphorus and metals in stormwater runoff are major causes of water quality degradation. Bioretention systems are increasingly implemented to improve stormwater quality and to better manage stormwater quantity. Many studies have focused on modifying the composition of the soil bed to improve pollutant removal. However, the pollutant removal performance of bioretention systems can diminish over time, such as when clogging of the media occurs. Sediment accumulation on the soil surface may inhibit infiltration into the soil bed, thus limiting pollutant removal. Soil replacement may be eventually required as pollutants accumulate in the soil. In this study, a green retrofit material, called green engineered mulch (GEM), was generated by coating regular wood mulch with aluminum-based water treatment residuals (WTR) via a simple and low-energy process (patent pending). The GEM was developed to serve as a green retrofit for bioretention systems to enhance the removal of phosphorus and metals from stormwater runoff. The GEM was placed in a rain garden in Secaucus, NJ, USA for 15 months, during which 12 storm events (ranging from 6.0 mm to 89.6 mm) were monitored. Runoff and infiltrate samples were analyzed for dissolved and total concentrations of phosphorus and metals, along with other key water quality parameters. The GEM significantly reduced (p < 0.05) the total concentrations of phosphorus and metals in stormwater infiltrate compared to the inlet, unlike the regular mulch. Minimal or no contact with the GEM resulted in no significant pollutant removal from surface runoff. No significant pollutant export from the GEM was observed. The spent GEM can be disposed of as non-hazardous waste in municipal landfills. This study demonstrates that the GEM is a safe and effective retrofit. Moreover, the GEM is a simple and economical retrofit solution that can be used in place of regular mulch in bioretention systems.

Experimental investigation on flexural and direct shear behaviors of specimens made of lightweight carbon textile‐reinforced cementitious composites

AbstractTextile‐reinforced cementitious composites (TRCCs) have recently received significant attention in structural engineering as promising retrofitting materials as well as reinforcements for thin and slender structural components. For applicability in the precast industry, the weight of the structural components made of TRCCs is a major concern. In this study, lightweight (LW) TRCC materials were developed and their flexural and direct shear performances were investigated. Carbon fabric is used as the textile reinforcement of the LW TRCCs, and expanded glass aggregates made from industrial refractory materials with fine particle sizes of 0.25–0.5 mm incorporating the mineral admixture (silica fume) are used to develop the LW cement‐based matrix. The main test series in this study include the expanded glass‐to‐binder (EG/B) ratio, surface coating methods used for textile fabrics, and volume dosages of short polyvinyl alcohol (PVA) fibers used to modify the cement‐based matrix. Three main series, including a total of 30 flexural test specimens and 30 shear test specimens, are fabricated and tested. The flexural behavior of LW TRCCs is investigated via four‐point bending tests and the direct shear behavior of LW TRCCs is investigated based on the FIP standard using one shear failure plane. The experimental results indicate that the EG/B ratio significantly affects the overall flexural and shear performances of LW TRCCs, wherein the use of higher EG/B ratios might lead to greater reduction in flexural properties as well as shear properties in the pre‐peak stage. The coating methods employed for fabric surface treatment via epoxy impregnation combined with rough layers are effective in enhancing flexural properties in terms of load and deformation capacity and shear properties in terms of peak stress compared with the counterpart using only the epoxy coating method. Additionally, incorporating short discrete PVA fibers within the LW cement‐based matrix results in outstanding performance due to improvement in bonding quality at the textile/matrix interface, which can be applied as a potential solution for fabricating LW, high‐performance TRCCs.

Shake-table testing and numerical simulation to select the FRCM retrofit solution for flexure/shear deficient RC frames

This paper presents shake-table and numerical investigations to select a retrofit strategy for reinforced concrete (RC) frame structures using fiber-reinforced cementitious matrix (FRCM) composites. Two FRCM alternatives are investigated, namely polyparaphenylene benzobisoxazole (PBO) and carbon FRCM composites, denoted as ‘P-FRCM’ and ‘C-FRCM’, respectively. The study focuses on implementing the selected retrofit material with spike anchorage systems to delay the debonding failure and addresses different failure modes of RC framing systems, including shear or flexure failure. The first phase of this study involves pre shake-table test (STT) simulation to investigate the effectiveness of the selected retrofit technique in delaying local and global damage states and failure modes. STT campaigns are undertaken in the second phase to assess the seismic performance of framing systems retrofitted with different FRCM materials and verify their fiber-based modeling approach. The verified numerical modeling approach of the retrofit techniques is utilized in the third phase to upgrade a benchmark RC moment-resisting frame (MRF) building. A parametric study involving inelastic pushover analyses (IPAs) and multi-record incremental dynamic analyses (IDAs) is finally conducted to assess the vulnerability of the retrofitted building with different FRCM alternatives. It is concluded that the adopted two retrofit techniques significantly reduced the collapse damage state at the design and maximum considered earthquake intensities by up to 59% and 46%, respectively. Although the P-FRCM composite has 38% higher tensile strength and 76% higher ultimate tensile strain than C-FRCM, it slightly improves the overall seismic performance by up to 9% based on the adopted seismic performance index. Owing to the higher cost of P-FRCM compared with its counterpart, a performance-to-cost index confirmed that the C-FRCM composite is the preferred retrofit technique for MRF structures.

Innovative techniques integrating advanced and bio-composite materials for energy and seismic retrofitting of built heritage

Cultural heritage is recognized as a driver of the sustainable development. The UNESCO’s 1972 World Heritage Convention has addressed key topics that link heritage practices to sustainability objectives. Historic buildings make up a considerable part of EU building stock, and their renovation and safeguarding require retrofit solutions that balance safety, energy efficiency, human comfort, heritage value preservation and environmental sustainability. This article tries to throw light on innovative techniques for heritage restoration based on sustainability, reuse, and recycle principles through non-invasive interventions. The work outlines the progress in the field of advanced materials obtained through the reuse of recycled materials, showing outcomes from MIRACLE research carried out by University of Florence on the development of an innovative fiber-reinforced bio-composite matrix to be applied for energy plus seismic retrofitting of existing masonry buildings built before 1945.

Ductility of Retrofit Column Using Wire Mesh and Self Compacting Concrete Due to Lateral Cyclic Load

Poor construction and ductility are the causes of structural damage and failure in earthquakes. Retrofitting is a way of repairing the damage and increasing the ductility of the column. Selection of wire mesh and self-compacting concrete as retrofit material, as it is easy to process and easy to obtain. The test specimen consisted of 3 columns with a size of 300x300 mm, consisting of a control column (KK), a completely retrofitted column (KR-1) and a retrofitted column in the approximate plastic hinge area (KR-2). The samples were cyclically tested based on the displacement control method. The test results show that the retrofitted with wire mesh and self-compacting concrete has a higher ductility value on the approximate plastic hinge area (KR-2). In addition, the retrofitted column has a higher load-bearing capacity than the column that has not been retrofitted.

STRENGTHENING OF RC BEAM USING CARBON FIBER REINFORCED POLYMER LAMINATES

Numerous factors, including I the need to upgrade existing structures as a result of infrastructure development, (ii) excessive deflection, cracking, and insufficient ultimate strength, (iii) the need to carry higher permissible loads, (iv) design flaws, (v) subpar building techniques, (vi) poor durability, etc., have made structural strengthening of reinforced concrete (RC) structural elements necessary. Structures or components may occasionally be overloaded, which results in increased cracking and decreased stiffness/strength. The repair and retrofitting of RC structural components can be handled using a number of well-liked procedures, including externally bonded steel plates, concrete jacketing, fiber-reinforced laminates or sheets, external pre-stressing, and external bar reinforcement techniques. Because to a significant mismatch in the tensile strength and stiffness of that material, strengthening employing CFRP has recently been found to be susceptible to unfavourable brittle failures. These restrictions are essential for selecting the right technology and material for strengthening. Each method or retrofit material has advantages and disadvantages of its own. Low strength to weight ratios, compatibility challenges between the parent and repair materials, corrosion and durability problems, and failure modes are the main drawbacks of these techniques.

Experimental Seismic Structural Performance Evaluations of RC Columns Strengthened by Stiff-Type Polyurea

Recently, strong earthquakes are continuously occurring all over the world regarding, repair and strengthening of non-seismically designed structures. Presently, fiber-reinforced polymer (FRP) surface-bonding method is used as a quick and easy way to retrofit and strengthen damaged columns and walls. However, the inherent problems of the FRP surface-bonding method of bond degradation are adhesive interfaces and FRP sheet aging during service-life still. In order to overcome these problems, it is necessary to develop new materials and techniques that can induce monolithic behavior between the structural member and retrofit material by eliminating the bonding interface. One solution is to use repair and strengthening using stiff-type polyurea (STPU) developed as a seismic retrofitting material which can be applied by spraying method. In order to investigate the retrofitting effect of STPU, pseudo-dynamic push–pull test and dynamic shaking table tests are performed. The novelty of the study is that the RC columns strengthened with a newly developed STPU are tested for pseudo-dynamic (i.e., also represents the static behavior) and dynamic behavior. From the test results, overall strengthening effect of the STPU for both static and dynamic loading conditions can be understood, which can be used for retrofitting of concrete structures all over the world. The study results are discussed in detail in the paper.

Parametric Studies on Dynamic Analysis of Blast-Loaded Retrofitted RC Columns

The majority of public and private facilities, existing today, were not originally designed to withstand blast loads rising from terrorist attacks. Hence, such facilities require effective countermeasures to minimize losses inflicted on property and people in the event of terrorist bombing. Retrofitting of main structural elements is very effective to increase blast resistance. In this paper, comprehensive parametric studies for the dynamic response of blast-loaded RC columns are performed using the proposed nonlinear coupled model and AUTODYN software. Many material and reinforcement parameters are considered in the paper such as concrete compressive strength, steel yield stress, longitudinal steel ratio and transverse stirrups ratio. Blast-loading parameters such as using different explosive weights, changing the stand-off distance of explosion, are also studied. Finally, the retrofitting parameters for blast-loaded columns, such as using different retrofit material types like the Carbon Fiber Reinforcing Polymers (CFRP), Glass Fiber Reinforcing Polymers (GFRP) and Steel Reinforcing Polymers (SRP) with different thicknesses for each material type, are considered. Important conclusions are drawn for the sensitivity of dynamic response and failure modes of RC columns under blast loading.