Envelope Retrofit Research Articles

Evaluating thermal performance of vertical building envelopes: Case studies in a Canadian university campus

Campus buildings at the University of Victoria (UVic) were largely constructed before the advent of building energy codes. The University is in the process of commissioning vertical building envelope upgrades/retrofits with added intention of addressing potential energy and greenhouse gas (GHG) savings in their building stock. The aim of this paper is to present the methodology adopted to evaluate potential energy savings from vertical envelope retrofits of 49 non-residential buildings across the campus portfolio, and to further validate those savings through more detailed energy models for a subset of buildings. To this end, the thermal performance of a building envelope was quantified based on its heat loss coefficient (UA), obtained from multiplying its surface area (A) by its thermal transmittance (U-value). Heat loss (UA) calculations were used as an energy loss metric to inform envelope rehabilitation prioritization, in addition to data gathered from building envelope condition assessments (BECAs). UA data were also analyzed against other building data such as floor area, vertical envelope area, vertical area to floor area ratio (VFAR), window-wall ratio (WWR), age, and type of construction for potential correlations. Finally, archetype energy models were used to evaluate the impacts of envelope retrofits on energy and GHG savings on three selected buildings. The outcomes of this study allow the University to weigh the benefits of improved energy performance from envelope retrofits against associated capital cost expenditures.

Precast Concrete Building Construction and Envelope Thermal Behavior: A Case Study on Portuguese Public Social Housing

A considerable part of Southern European countries building stock was constructed before the implementation of national thermal regulations, and as such, it is currently exposed to challenges such as energy poverty and climate change. Portuguese public social housing presents a significant variety of construction systems and applied typologies. Among them, the “Novobra NK1”, a precast concrete construction system that exploits some innovative features in envelope components, has been used in several projects. Considering the importance of retrofitting to improve and adapt the thermal behaviors of buildings to face the aforementioned challenges, this article aims to provide an understanding of the behavior of a NK1 thermal envelope of a dwelling located in Covilhã, Portugal, and the impact of some constructive envelope retrofit measures applied. Results show that existing opaque envelope elements and glazed areas present characteristics that are no longer able to provide proper responses to contemporary building constructive requirements. External insulation was identified as a key retrofit measure, window replacement also being an advised solution for rigorous heating seasons. Improvements from the internal side of windows, such as roller shades, may provide few benefits during cooling seasons, and applying solar films is not advised without a proper thermal repercussion analysis.

Potential benefits and optimization of cool-coated office buildings: A case study in Chongqing, China

Increasing envelope facet albedos considerably reduces solar heat gain, thus yielding building cooling energy savings. Few studies have explored the potential benefits of utilizing cool coatings on building envelopes (“cool-coated buildings”) based on life-cycle cost analysis. A holistic approach integrating the field testing, building energy simulation, and a 20-year life-cycle-based optimization was developed to explore cool-coated building performance and the maximum net savings of optimal building envelope retrofit and design. Experimental results showed that applying cool coatings to a west wall of an office building in Chongqing, China reduced its exterior surface temperature by up to 9.3 °C in summer. Simulation results showed that in Chongqing, making the roof and walls cool could reduce annual HVAC electricity use by up to 11.9% in old buildings (with poorly insulated envelopes) and up to 5.9% in new buildings. Retrofitting old buildings with a cool roof provided the net savings per modified area with present values up to 42.8 CNY/m2; retrofitting a new building with a cool roof or cool walls was not cost-effective. Optimizing both envelope insulation and envelope albedo can achieve 5.6 times the net savings of optimizing the insulation only, and 1.6 times that of optimizing albedo only.

A novel reduced order model technology framework to support the estimation of the energy savings in building retrofits

Energy Performance Contracting (EPC), as a tool to enhance energy efficiency of buildings, can accelerate investment in cost-effective energy conservation measures (ECMs) for existing buildings. However, there are many risks and barriers that can slow down the uptake of EPC, such as the complexity of the process or uncertainty of building performance post-retrofit. The International Performance Measurement and Verification Protocol (IPMVP®), which was originally developed to help increase investment in energy and water efficiency, demand management and renewable energy projects, has the potential to reduce some of the EPC barriers. However, due to limited and uncertain information about existing buildings, the application of this Measurement and Verification (M&V) protocol in retrofitting projects is often complex and requires novel use of building simulation tools.In order to address the challenges of utilising M&V IPMVP® in building retrofitting projects, and to enhance the uptake of EPC, the research presented here developed a novel Reduced Order Model (ROM) technology framework that can be used for (i) systematic quantification of energy savings (avoided energy consumption) achieved through ECMs, and (ii) direct estimation of energy savings through the investigation of different envelope retrofit scenarios. The framework was demonstrated on pilot buildings in Sant Cugat, Spain.

A modelling approach and a case study to answer the question: What does it take to retrofit a community to net-zero energy?

In order to have an immediate impact on building energy-related emissions, existing buildings need to be addressed. To inform policy and technical decisions, detailed mathematical models are required which can explore numerous building retrofit solutions and their energy and emissions performance. This paper describes the adaptation of a hybrid statistical and engineering-based model for residential building stock in Canada to analyze community-scale energy retrofits. The modelling domain includes both envelope and mechanical retrofits, as well as district renewable energy systems. This model is then applied to a case study of converting a community of fifty 1980’s vintage single-detached homes to achieve net-zero energy. The case study demonstrated that deep envelope retrofits and fuel switching from natural gas to electric heat pump systems reduce community energy demand by 69%. Saturating available roof area with photovoltaics was able to achieve net-zero balance. By considering net-zero at the community-scale, individual buildings that did not achieve net-zero were offset by net-exporting neighbours. Annual community emissions of the retrofit reduced emissions by 95%. The analysis also highlights the significant impact on electrical infrastructure due to solar generation and energy demand mismatch.

Building Envelope Thermal Defects in Existing and Under-Construction Housing in the UAE; Infrared Thermography Diagnosis and Qualitative Impacts Analysis

The built environment accounts for the highest share of energy use and carbon emissions, particularly in emerging economies, caused by population growth and fast urbanization. This phenomenon is further exacerbated under extreme climatic conditions such as those of the United Arab Emirates, the context of this study, where the highest energy share is consumed in buildings, mostly used in the residential sector for cooling purposes. Despite efforts to curb energy consumption through building energy efficiency measures in new construction, substantial existing building stock and construction quality are left out. Construction defects, particularly in the building envelope, are recognized to affect its thermal integrity. This paper aims, first, to detect through thermography field investigation audit construction defects bearing thermal impacts in existing and under-construction residential buildings. Then, through a qualitative analysis, we identify the resulting energy, cost, and health impacts of the identified defects. Results indicate that lack or discontinuity of insulation, thermal bridging through building elements, blockwork defects, and design change discrepancies are the recurrent building and construction defects. The qualitative review analysis indicates substantial energy loss due to lack of insulation, thermal bridging with cost and health implications, while beneficial mitigation measures include consideration of building envelope retrofitting, skilled workmanship, and the call for quality management procedures during construction.

A new framework to select energy-efficient retrofit schemes of external walls: A case study

Abstract Retrofitting energy-inefficient external walls would improve the energy performance of building envelope by utilizing new insulation materials to decrease heat transfer. However, previous researches mainly based on environmental and economic considerations are still partial and could hardly provide a holistic perspective for the optimal selection of external walls retrofit techniques. To address this problem, this paper proposes a novel heterogeneous multi-criteria group decision-making (MCGDM) framework in which the ratings of schemes are described with real numbers and linguistic variables and the weights of criteria are unknown. Firstly, an evaluation index system is established covering criteria of thermal insulation property, technique, durability, and economic efficiency. Secondly, building information modeling (BIM) is utilized to determine multiple retrofit schemes and derive the heat transfer coefficient. Thirdly, after heterogeneous evaluation values are unified, a combined weighting approach is developed based on best worst method (BWM) and the similarity method before fuzzy VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method is applied to rank the alternatives. Fourthly, the applicability of the proposed framework is demonstrated by a case study of the external wall retrofit scheme selection in Beijing, which reveals that extruded polystyrene (XPS) and expanded polystyrene (EPS) insulation schemes are the compromise choices with aggregating index Qk of 0.0032 and 0.0967 respectively, while rock wool insulation scheme is the last option with Qk of 0.7182. The stability of ranking results is proved with the changing weight of maximum group utility, and the effectiveness of the proposed framework is verified by a comparative analysis. This study can facilitate the implementation of building envelope retrofit by providing useful guidance for selection of external wall retrofit schemes.

Exploring membrane-assisted radiant cooling for designing comfortable naturally ventilated spaces in the tropics

ABSTRACT This research proposes the use of membrane-assisted radiant panels to improve the thermal comfort of naturally ventilated spaces in hot and humid climates. These radiant panels are capable of conditioning naturally ventilated spaces, which is impractical with conventional mechanical cooling systems. For conventional systems, a permeable envelope will result in energy wastage from conditioned air escaping or condensation occurring on the radiant surfaces. In our system, there is no air-conditioning and we avoid condensation by separating the radiant surfaces from humid air using a membrane transparent to thermal radiation. The membrane-assisted radiant panels are an unutilized technology for architects to design comfortable naturally ventilated spaces. We propose a cooling system based on the technology and discuss the architectural implications, particularly the permeability of the building envelope and requirements for mechanical spaces, of employing this system in a case study that is a naturally ventilated classroom. Our system is compared to conventional cooling systems. Although our system requires a ceiling space reconfiguration, it does not require duct works and envelope retrofits. The comparative case study shows a potential 52% reduction in cooling energy demand from initial estimation. Considering the trade-offs, our system can be a good alternative for retrofit projects.

Optimizing Urban Texture and Building Typology for the Goal of Achieving Near-Zero Mid-Rise Residential Building

Turkey is experiencing a massive urban renewal process to increase earthquake resistance of building mass. As a participant of Paris Agreement, Turkey also uses this process as a tool to improve energy saving performance of building mass with mandatory insulation requirements. Envelope retrofits achieves energy savings; however, this massive urban renewal process offers a greater potential since it allows a chance to optimize urban scale variables such as urban texture and building type, as well. This paper focuses on investigating the influence of building typology and urban texture on building energy performance. For this purpose, four different texture and six different building type alternatives are defined in Istanbul. Energy performance simulation analysis of 24 total alternatives are done with Existing envelope, TS-825 envelope, and proposed Near-Zero envelopes. Results of 72 simulations show that both building type and urban texture have important influence on building energy consumption and production performances for three envelope alternatives. Selection of optimized building type and urban texture alternatives with N-zero envelope maximizes building energy performance and achieve near-zero building requirements. Another important result of the study was urban scale decisions reduces energy consumption very significantly even before applying building design strategies. This is a very important input for decision-makers because energy performance of a regular building can be improved with retrofits in any time during lifetime. However, these retrofits may not be enough to achieve full potential (net-zero in future time) of the building when urban texture and building type is not optimized accurately.

An integrated 3D GIS-based method for estimating the urban potential of BIPV retrofit of façades

To foster urban energy transition needed to limit the growing climate change’ effects, the urban BIPV retrofit of façades can play a significant role thanks to the transformation of the existing energy-intensive building sector into an efficient energy producer. However, currently, there is a lack of tools for the evaluation of such potential mainly because it relies on several fragmented and heterogeneous urban data. Nevertheless, to exploit the not-negligible contribution of retrofitting façades with BIPV in urban energy transition, the assessment of this potential at the urban level should be considered. Therefore, this paper presents a novel integrated 3D GIS-based methodology for the evaluation of this potential, especially for the Swiss context and multi-family house buildings by combining data for the evaluation of the envelope retrofit potential and by increasing the accuracy of the assessment of the BIPV façade potential beyond typical LOD2. Moreover, it includes GIS-based tools for evaluating the BIPV façade potential, the energy retrofit potential of envelopes, and the annual and seasonal urban energy balance. Finally, implementation’ results show that increasing the urban data’ accuracy can significantly affect the urban BIPV retrofit potential of façades, thus providing new crucial information for energy planning.

Integrated cost-optimal residential envelope retrofit decision-making and power systems optimisation using Ensemble models

The dynamic integration of building energy models and power system models is essential to analyse the potential supply-side benefits of adopting Energy Conservation Measures (ECM) at the national, regional scale. The integration of these models requires the development of linear building energy models which are numerically compatible with linear power systems models. Ensemble Calibration is an automated model calibration methodology which identifies a cluster of lumped parameter building energy models (denoted Ensemble models) using an archetype building energy model. Each lumped parameter building energy model represents an ECM configuration (i.e., a combination of ECMs). The current paper introduces a novel mechanism by which Ensemble models are integrated with power systems models in a manner such that cost-optimal retrofit decision-making problems and power systems optimisation problems can be simultaneously solved. To achieve this objective, Ensemble models are reformulated as bi-linear models, which are then co-optimised with power systems models using a multi-stage optimisation algorithm. The methodology is tested using two building energy archetypes: a detached house archetype and a mid-floor apartment archetype. The archetypes are representative of the Irish residential stock built prior to 1970. The results show that the proposed multi-stage optimisation algorithm provides computational advantages to the solution of the equivalent problem using a brute force approach (i.e., solving building-to-grid models for each ECM configuration). The proposed method is 4.73 times faster than the brute force approach when the archetypes are decoupled and 73 times faster when the models are deemed to be coupled via a power systems model.

Data driven process for the energy assessment of building envelope retrofits

In the last decades, a growing industry has been created in relation to building envelope retrofits. Linked to the lack of financial capacity of many building owners, innovative instruments such as energy performance contracts have been promoted by public bodies. This kind of instruments require of detailed energy assessment processes in order to define the expected heat load reduction and the associated economic flows between building owners and Energy Services Companies. When dealing with building envelopes, existing methods for building envelope heat loss characterization require of substantial efforts in terms of equipment and time, which makes them difficult to apply in real practice. In this paper, a novel method is proposed based on whole-building heat load assessment by means of heat meters, and analytical calculations of building envelope transmission heat load coefficients. This method, which requires minimal or no additional equipment, can be used over historical data from District Heating systems. It assigns a specific load fraction to building envelope heat transfer and allows to assess the expected reduction due to the building envelope retrofit. Numerical and experimental data is presented based on an educational building in the city of Burgos, Spain.

Combined geospatial and techno-economic analysis of deep building envelope retrofit

In this study, the Swiss residential building stock model (SwissRes model) is used to conduct a geospatial analysis of the techno-economic potential of deep building envelope retrofit packages in Switzerland. Element and building characteristics of 8242 archetype buildings are combined with high-resolution spatio-temporal weather data. We estimate final energy demand before and after retrofit, while correcting for the energy performance gap. Levelized costs of energy savings are calculated in two ways, i.e. based on full costs and investment cost related only to thermal improvement of the envelope. Results show that, technically, a 57% reduction of the final energy demand for space heating could be achieved with the deep envelope retrofit. For full costs, less than 1% of these measures would be cost-effective, whereas for improvement costs nearly the full retrofit potential is cost-effective. We identified primarily rural and mountainous regions as well as historic city centres to show highest cost-effectiveness.

Cost-optimal retrofit analysis for residential buildings

The current retrofit rate in Switzerland is very low. Among other reasons this is attributed to a lack of knowledge about cost-optimal retrofit strategies. In this work we carry out a holistic cost-optimal retrofit analysis for a Swiss single-family house. First, currently popular retrofit measures including all incurring lifecycle costs are identified and collected. Thereby, building systems as well as building envelope retrofit measures are considered. The retrofit measures are then combined to form a wide range of applicable retrofit strategies which are assessed in terms of cost-effectiveness and environmental impact. The calculation methodology considers the impact of building envelope retrofit measures on the design and efficiency of the heating system. For the case study building, the most cost-optimal retrofit strategy is to combine a geothermal heat pump with inter-rafter roof insulation and cellar ceiling insulation. The results indicate that the choice of heating system is much more crucial in terms of cost-effectiveness than building envelope measures. With respect to reducing primary energy consumption, building envelope measures are indispensable, however, when aiming for reducing greenhouse gas emissions, the choice of heating system becomes dominant.

Energy performance optimisation of building envelope retrofit through integrated orthogonal arrays with data envelopment analysis

Retrofitting building envelopes is regarded as an effective solution that can help commercial and individual investors offset daily power usage. However, it is worthwhile to explore a highly efficient approach to seek optimum retrofitting strategies. A novel hybrid approach that integrates energy simulation, Orthogonal Array Testing (OAT), and Data Envelopment Analysis (DEA) is developed in this research to discover optimal solutions for building retrofit. A commercial high-rise building is chosen as a case study, and five parameters are considered, including the exterior envelope fabric, exterior window type, sunshade type, window-to-wall ratio, and airtightness. The energy consumption is first simulated and verified as a baseline. OAT is then employed to conduct experiments and explore potential solutions to the energy optimisation problem, based on which the most efficient strategy is obtained through DEA benchmarking. The identified optimal solution is able to save an annual operation energy of 7.01 kWh/m2, which is also cost-effective. It is also found that the window type and airtightness are significant factors with regard to the energy performance of building envelope retrofit. The study benefits designers and construction managers in determining the optimal solution of retrofitting building envelope for achieving energy-efficient building operations.

Towards Resilience and Sustainability for Historic Buildings: A Review of Envelope Retrofit Possibilities and a Discussion on Hygric Compatibility of Thermal Insulations

ABSTRACT Our historic heritage needs to be prepared to face the new challenges imposed by climate change. A possible way to meet this urgent need consists in improving buildings resilience and energy efficiency through envelope refurbishment interventions. Consequently, an overview of the existing solutions for envelope retrofits in historic buildings is provided and their suitability for preserving valuable constructions is discussed. Thermal insulation solutions appear as the most discussed interventions and, therefore, their compatibility is considered in detail, accounting the hygric point of view. First, a general, rough criterium is introduced for ranking their hygric behaviour, according to their vapour permeability and capillary absorption coefficient, through a comparison with the average hygric characteristics of some historic building materials. Then, a method for performing fast, preliminary compatibility assessment is proposed, based on the definition of target interventions (qualitative hygric requirements) for specific clusters of situations (type of intervention, component, boundary conditions).

“PET tool” – a software tool for lightweight extensive green roofs performance analyses

Due to energy, environmental, and social benefits, green roofs are recognized as a bioclimatic technology and sustainable construction systems and are becoming a predominant solution in connection with urban planning and building envelope retrofitting. To support design and marketing of Urbanscape® lightweight extensive green roofs a special software tool was developed, which is presented in the paper. Performance evaluation tool (PET tool) is validated based on extensive and continuous 5-years in-situ monitoring of thermal and hydrological response of different Urbanscape green roofs. The key performance indicators of Urbanscape green roofs are evaluated based on calculated thermal and hydrological response. To emphasize the advantages of green roofs thermal response and performance indicators are determined also for non-vegetated roof for the same boundary conditions. PET tool enables i) evaluation of Urbanscape green roofs’ whole year thermal and hydrological response, ii) to search for the optimal design of the Urbanscape green roof system in terms of energy and water performance, iii) evaluation of comparative advantages compared to non-vegetated roof, iv) energy savings and CO2 emission reduction analyses for heating and cooling season. Analyses can be made for arbitrary worldwide climate conditions since meteorological parameters are gathered from Meteonorm database.

Envelope retrofitting strategies for public school buildings in Jordan

The purpose of this research is to study and develop envelope retrofitting strategies for uninsulated school buildings in Jordan built before the educational reform; to date, more than 2917 of these buildings have continued to function. The proposed envelope retrofitting alternatives are analyzed in terms of potential energy savings and initial cost, based on which a holistic approach to envelope retrofitting is developed by combining energy-efficient and economically feasible retrofitting alternatives. The study adopts a multi-dimensional research design strategy, which includes mixed design methods—quantitative and qualitative. These methods include physical analysis, national archives, questionnaires, and field monitoring of environmental parameters inside classrooms. Energy simulation and economic analysis using the simple payback period analysis method are performed. The effects of the research strategies before and after their applications are used to assess the efficiency of envelope retrofitting. The findings indicate that the proposed approach to envelope retrofitting leads to energy savings of up to 54% with a payback period of 5.5 years. Finally, the application of the proposed retrofitting approach to public school buildings with various service lives is investigated.

Building Envelope Thermal Upgrade for School Buildings in Jordan

Following the educational reform in Jordan in 2003, the government decided to cease the construction of old, prototypical, and uninsulated schools in favor of thermally insulated site-specific buildings. However, more than 2917 uninsulated school buildings built before the reform have continued to function. Therefore, this research focuses on evaluating and comparing the thermal efficiency of the envelope of old, uninsulated prototypical schools with that of thermally insulated, site-specific school’s buildings in Jordan. Furthermore, it will develop envelope retrofit strategies for the remaining 2917 uninsulated schools. The proposed envelope retrofit alternatives will be analyzed in terms of potential energy saving and initial cost, based on which a holistic approach is developed by combining energy-efficient and economically feasible retrofitting alternatives. The research here uses mixed design methods to fulfill its purposes, including data collection from the literature and national archives, self-reported data, field monitoring of environmental parameters inside classrooms, and energy simulation using (Design Builder) software, in addition to economic analysis using the simple payback period analyses method. Based on analyses, a holistic approach to envelope retrofitting was developed for old governmental school models in Jordan, based on an analysis of the effects of the enhancement of envelope parameters on annual cooling and heating energy saving (walls, roof insulation, roof reflectance, windows, and shading elements). The proposed alternatives to envelope retrofitting for each envelope parameter was analyzed in terms of potential energy saving and initial cost analysis.

A Life-Cycle Approach to Building Energy Retrofitting: Bio-Based Technologies for Sustainable Urban Regeneration

The construction sector and, more specifically, the building renovation sector plays a decisive role in the achievement of the EU targets for the reduction of energy consumption and CO2 emissions. The main strategies implemented by the EU are aimed, on one side, at increasing the number of buildings to be renovated and, on the other, at promoting deep renovation on the existing stock. The main objective is to drastically reduce the CO2 emissions associated with the energy consumption of buildings during their operation in consideration of the decarbonization targets by 2050. Several studies have shown that around 75% of the EU building stock needs energy retrofitting, and a significant amount of thermal insulation is expected to be installed on the building envelopes in order to decrease the energy losses. The carbon emission for the production of materials and construction might slow down the transition to a low carbon society and significantly reduce the carbon budget available by 2050. In this perspective, the paper shows the results of some recent research activities aimed at identifying alternative approaches based on the use of biogenic materials applied to the building envelope retrofitting. On one side, they meet the energy and CO2 targets established by the EU while promoting, on the other one, sustainable regeneration processes that include, among the others, the storage of CO2 in building elements and the efficient land use. A specific calculation tool, based on a dynamic LCA method, is introduced to holistically quantify the environmental benefits expected over time.