Search

European Union policies are encouraging the implementation of renewable energies to reduce fossil fuels dependency. This is further motivated by the effects of global warming and the relevant temperature rise in large cities. Thus, it is increasingly important to analyze the large-scale potential of solar energy, making use of the roof availability for renewable energy generation in cities. Furthermore, it is important to couple this analysis with the energy demand of the buildings analyzing the self-consumption possibilities and help in the decision-making process in regional investments. The proposed methodology estimates and matches the roof potential for electricity generation by PV and the building's energy demand, including the building characteristics as a novelty. As a result, we calculate the self-consumption possibilities and the retrofit requirements of a selected housing stock. Our methodology starts with the quantification and classification of the residential stock. This includes the characterization of the types of dwellings in the regional residential stock, taking into account the size of the municipalities. Then the energy demand of the dwellings, depending on the characteristics of the buildings and the roof generation potential, is compared. Catalonia region (Spain), including the city of Barcelona is studied to show the contributions of this methodology to the energy transition. Results indicate that between 8 and 30% of the residential electricity demand of the municipalities can be covered by rooftop PV. Important energy retrofits (reductions of 80% of the energy demand) are required to approach the feasibility of self-consumption. Nevertheless, there is a limited potential impact in larger cities due to the reduced available roof area per habitant.

Coordinated large scale building retrofit is one of the most effective approaches not only to reduce the environmental footprint of existing buildings but also to assure that climate goals can be met. Existing bottom-up retrofit approaches become infeasible or lack in terms of accuracy and/or computational cost especially when the scale of application increases in size. Hence, the aim of this paper is to propose and develop a bottom-up approach for large-scale building retrofit with the use of a scalable building-level surrogate retrofit model. To ensure scalability and generalization to large areas, we use artificial neural networks. The developed approach consists of a set of artificial neural networks trained on building archetypes, aiming to predict near-optimal building retrofit solutions for all residential buildings in Switzerland. This is achieved with a small set of inputs, and within a short run time. In order to validate the developed approach, we compare it with a conventional mixed building simulation and optimization approach. The surrogate model computes near-optimal building retrofit solutions, with an average coefficient of determination of 0.91 and an average f1 score of 0.89. To illustrate the advantages of this model, we perform a large-scale retrofit analysis of a case study in Geneva municipality. Such a surrogate model is capable of providing insights into the overall retrofit potential of large areas and thus shall support reaching energy emission reduction targets of existing residential buildings., Applied Energy, 333, ISSN:0306-2619, ISSN:1872-9118

This research presents a methodology for measuring acoustic comfort using a soft-sensing approach to support decision-making for buildings renovation. The soft-sensor provides a measurement system for evaluating indoor acoustic quality of buildings (housing, schools, offices, etc.) in relation to the external noise level. The metric is represented by Key Performance Indicators (KPIs), which quantitatively express the acoustic comfort. Information regarding the current condition of the building (“As-is” KPI) is provided as a normalised value for the simplified quantification of acoustic performance. The knowledge of the “As-is” KPI allows the design team to compare it with the new KPIs obtained from renovation scenarios (“What – if” KPI). A case study is presented to demonstrate the exploitability of the methodology. Sensitivity and uncertainty analyses are performed to establish how the accuracy of the KPI measurement impacts on the decision-making process. The methodology shows promising results in the identification of the best retrofit strategy.

Recent architectural trends in high-rise residential buildings are favoring more transparent facades with fully glazed exteriors. While aesthetically pleasing, high window to wall ratios (WWR) entail significant discomfort due to higher solar heat gains and heat losses. In this architectural context, passive latent heat thermal energy storage (LHTES) is a possible solution to regulate indoor thermal comfort by limiting the room temperature swings. This study investigates the effectiveness of adopting Phase Change Materials (PCMs) in retrofitting high-rise apartments with 80% WWR. A composite PCM system, comprised of two PCM products with melting temperatures of 21.7 °C and 25 °C is introduced to provide thermal energy storage across the year. The phase change cycle of the PCMs and their impact on indoor air and interior building surface temperatures are assessed. For this, two test cells were constructed, one acting as a baseline and another enhanced with the composite PCM system positioned on the walls and the ceiling. The results indicate improved performance of the test cell containing the composite PCM system in lowering peak indoor and surface temperatures up to 6 °C. The melting and solidification patterns of the PCMs showed a close correlation with peak solar heat gain and heat loss periods respectively. The benefits of the PCMs were more pronounced in stabilizing indoor cell temperatures in extreme conditions with sharp temperature variations. Aspects such as the effectiveness of night natural ventilation and shading design optimization were also assessed.

On the basis of a representative set of examples, we tackle following issues concerning the energy performance gap which is commonly observed in retrofit of multifamily buildings: quantification of the main factors behind the gap, in relation with simulation; decomposition of the gap, by combination of the most sensitive parameters, in relation with observed values; exploration of how to bridge the gap, on the basis of two best practice examples. The results show that the gap consists of: (i) the difference between optimal yet realistic conditions of use, and standard values used in the simulation process; (ii) the difference between actual and optimal conditions of use, which corresponds to the optimization potential. It proves that significant reduction of the performance gap is possible through building optimization and responsible behavior.

This paper presents an energy conservation measures prioritization process of a residential Australian building. For this purpose, a simulation model of the building has been implemented and validated based on the information from the energy audit report. Further, a preliminary set of potential energy conservation measures has been identified according to specific information collected during the building survey phase. DesignBuilder software has been used as the simulation tool and yearly energy benefits have been quantified for each intervention. Finally, an economic assessment is conducted based on the most common economic tools (net present value, internal rate of return, profitability index and discounted payback period). As a consequence, a final building performance simulation has been conducted in order to properly quantify the potential energy benefit of the whole retrofit intervention. As results, this study highlights how arduous could be, in certain cases, to achieve a cost-effective retrofit intervention and how economic indexes could bring users to exclude a priori certain energy conservation measures during decision-making process even when these interventions are necessary to improve thermal comfort and energy efficiency.

Building retrofit is a main concern to reach EU de-carbonisation goals of 2050. Facade retrofit plays a pivotal role in the reduction of energy consumption in buildings: several strategies are in fact available, both in terms of on-site systems and prefabricated elements. The research question arising regards therefore how to choose the best-suiting residential retrofit strategy between different technological systems. In this sense, a current lack of diffusion of Decision Support Systems between can be underlined, as decisions mainly derive from previous experiences. An optimizing strategy that could express the goals of the many actors involved in the building process is required. In order to consider the impact of different criteria on the choice, multi-criteria methodologies could be effective. Existing similar methods mostly focus uniquely on energy performance, or follow the categories of environment, economy and society. What is currently lacking in available tools regards production-linked and technological aspects, related to e.g. facade morphology, and building site features. The aim of this paper is to identify relevant parameters related to installation and economy aspects, for a multi-criteria approach to be used in the choice of the most suitable building retrofit strategy. The methodological approach is therefore provided, and the choice of parameters, carried out by means of interview with actors of the building process, is explained. The criteria selection and the subsequent criteria weighting phase is to be carried out by means of interviews and surveys to the actors involved in the building process. The application on case-studies will offer the opportunity to assess the effectiveness of the method.

This paper focuses on the benefits on the local microclimate and the building energy saving resulting from green roof retrofits. The research investigates a case study located in a university campus in Toronto, Canada. After completing a detailed energy audit of the building, an assessment of the benefits resulting from the installation of an extensive green roof was performed. A virtual model validated using multiyear data of a local network of different weather stations was used to simulate the effects of the green roof retrofit over the outdoor microclimate. Then, a building energy model was used to compare the energy saving of several green roof designs. Results indicate that increasing the leaf area index (LAI) would lead to an increased cooling effect of the air temperature up to 0.4 °C during the day at pedestrian level, while a more significant temperature reduction would be obtained only at the rooftop level. This confirms the potential of green roofs as urban heat island mitigation strategy. The adoption of a green roof retrofit resulted in a building energy demand reduction by 3%, and in significantly improved indoor comfort levels in the floor below the green roof. Finally, the parametric analysis of different green roof options showed that for building energy savings, increasing the soil depth is more important than increasing the LAI.

The thermal performance gap in buildings is defined as the difference between the theoretical and the actual energy consumption for heating, and is known to undermine energy retrofit strategies and policies. This study examines the performance gap in retrofitted buildings using the Swiss Cantonal Energy Certificate for Buildings (CECB) database, using a sample of 1172 buildings for which both theoretical and actual metered consumption were known. We found an average negative performance gap of –23% for pre-retrofit buildings (actual consumption smaller than calculated) and instead a good approximation of actual consumption with theoretical consumption after retrofitting (a positive gap of 2%). A regression analysis on the energy performance certificate input parameters characterizing the building led to the conclusion that these are poor predictors of actual consumption compared to the theoretical calculation: parameters such as the energy label and the thermal proprieties of the envelope (U-values) have minor explanatory power for the actual consumption despite explaining a high degree of change in the theoretical consumption. Analysis of the indicator Energy Savings Deficit (ESD) shows an overestimation (of 37%) of the achievable savings on the basis of the theoretical consumption, whereas the prediction of savings using measured consumption before retrofit resulted in a good agreement with the actual savings (3.6% overestimation). This implies that energy savings can be estimated rather accurately by comparing the actual current consumption with the expected theoretical consumption defined by the certificate after retrofit., Energy and Buildings, 224, ISSN:0378-7788, ISSN:1872-6178

An existing industrial building ubicated in South Italy is investigated by applying a tailored approach to optimize energy retrofit. The baseline provides high energy consumption, which needs to be tackled to promote the transition towards more sustainable buildings. Accordingly, after a detailed energy audit, the building is modeled and simulated under EnergyPlus environment using DesignBuilder® to characterize geometry and HVAC (heating, ventilating and air conditioning) systems. The model is calibrated against metered data as concerns the trends of indoor temperatures. Different retrofit measures are investigated, i.e., replacement of windows, implementation of solar screens, use of heat recovery, optimization of HVAC operation and installation of photovoltaics of different sizes. Thus, a large domain of solutions is explored by conducting an exhaustive research through the coupling between EnergyPlus and MATLAB®. The research provides the Pareto optimization of building retrofit minimizing primary energy consumption and global cost for two different scenarios as regards the access to public incentives. The utopia point criterion is used to pick a solution from the Pareto front. Such solution can yield energy and global cost savings up to 81% and 45%, respectively, ensuring the same comfort level compared to the baseline. The primary energy consumption of the whole facility can be reduced up to 40.1 kWhp/m2a. The outcomes can give precious guidelines to refurbish industrial and office buildings in Mediterranean areas with a view to energy-efficiency and cost-effectiveness.

The energy retrofitting of existing buildings reduces the energy use in the operation phase but the use of additional materials influence the energy use in other life cycle phases of retrofitted buildings. In this study, we analyse the life cycle primary energy implications of different material alternatives when retrofitting an existing building to meet high energy performance levels. We design retrofitting options assuming the highest and lowest value of final energy use, respectively, for passive house standards applicable in Sweden. The retrofitting options include the thermal improvement of the building envelope. We calculate the primary energy use in the operation phase (operation primary energy), as well as in production, maintenance and end-of-life phases (non-operation primary energy). Our results show that the non-operation primary energy use can vary significantly depending on the choice of materials for thermal insulation, cladding systems and windows. Although the operation energy use decreases by 63–78%, we find that the non-operation energy for building retrofitting accounts for up to 21% of the operation energy saving, depending on the passive house performance level and the material alternative. A careful selection of building materials can reduce the non-operation primary energy by up to 40%, especially when using wood-based materials.

Energy Efficient Scotland (EES) is the Scottish Government's flagship programme for the national-scale retrofitting of buildings over the next 15–20 years. This is a critical component of Scotland's commitment to net zero greenhouse gas emissions by 2045, that will also help to reduce fuel poverty and improve local economies. The success of EES is reliant on partnerships between local authorities, arms-length external organisations, charities, and social enterprises. However, little is known about how these organisations collaborate for the delivery of building retrofit. This paper analyses interview data from local authorities and these delivery partners, conceptualising them as part of linked ecologies, or interconnected networks of professional groups. EES is identified as a hinge that holds distinct meanings for different parties; it supports learning between local authorities and delivery partners, but does not guarantee the alignment of priorities. The concept of avatars, or individuals and skills that travel between organisations, reveals the search for relevant internal knowledge amongst local authority officers, whilst external delivery partners amass expertise for retrofitting. To ensure successful national-scale building retrofit, policy makers will need to develop shared databases, and clear guidance for the allocation and distribution of resources and responsibilities between local authorities and delivery partners.

Energy efficiency in the demand side is considered one of the cheapest ways to achieve reductions in Green House Gases emission, as well as to avoid heavy investments in production, transmission and distribution of electricity. In the context of the Emirate of Abu Dhabi, UAE, where buildings (residential, office, retail and villas) consume about 87% of the electricity, most of which is devoted to indoor air-conditioning, energy efficiency has a huge potential for development. Under the current political/economical scenario, a series of measures to diversify the economy and attract expatriates are in place. These include heavy subsidies on retail electricity prices—which has the side-effect of limiting the economic feasibility of investments in energy efficiency. In this study, a series of building retrofits were tested on a model of the average office building in the Emirate. The best performing retrofit was identified to be the chiller's Coefficient of Performance (COP) improvements, having the lowest cost/benefit ratio and resulting in an overall annual electricity savings of around 12%. Under the current subsidized electricity price, investments in energy efficiency of existing buildings are not attractive for the owner-consumer, as over the lifecycle of the measure, the return on investment is low or negative. In this paper we attempt to assess the applicability, in the Emirate of Abu Dhabi, of energy saving obligations and tradable white certificates as a mechanism to enable investment in demand-side energy efficiency and achieving average investment returns of 7% over a 25 years horizon. The application of white certificates can enable the market of energy efficiency to develop in the Emirate. The economic return of applying a chiller retrofit under the studied white certificate scenario avoids the increase of 17% of current electricity prices.

The enhancement of the energy performance of the existing buildings stock is nowadays a priority. To promote buildings energy renovation, the European Committee (2010) [1] asks Member States to define retrofit strategies finding cost-effective solutions. This so-called cost-optimal approach, described by the Commission Delegated Regulation EU (European Commission, 2012) [2], pursues a balance of energy and economic targets, but currently neglects some important aspects, such as indoor thermal comfort. This research investigates the relationship between the initial characteristics of residential buildings and the definition of optimal retrofit solutions in terms of either maximum economic performance, or energy consumption minimization towards nZEBs behaviour for the lowest achievable thermal discomfort. A multi-objective optimization has been carried out using a genetic algorithm (NSGA-II) coupled with a dynamic simulation tool. The results demonstrate that (i) with conventional Energy Efficiency Measures, it is possible to approach the zero energy target maintaining the economical convenience but worsening the indoor thermal comfort and that (ii) there is the necessity to introduce incentives to foster solutions not economically profitable, but more efficient in terms of energy savings and indoor thermal comfort.

The reduction of energy consumption for heating and cooling services in the existing building stock is a key challenge for global sustainability today and buildings’ envelopes retrofit is one the main issues. Most of the existing buildings’ envelopes have low levels of insulation, high thermal losses due to thermal bridges and cracks, absence of appropriate solar control, etc. Further, in building refurbishment, the importance of a system level approach is often undervalued in favour of simplistic “off the shelf” efficient solutions, focused on the reduction of thermal transmittance and on the enhancement of solar control capabilities. In many cases, the importance of the dynamic thermal properties is often neglected or underestimated and the effective thermal capacity is not properly considered as one of the design parameters. The research presented aims to critically assess the influence of the dynamic thermal properties of the building fabric (roof, walls and floors) on sensible heating and cooling energy demand for a case study. The case study chosen is an existing office building which has been retrofitted in recent years and whose energy model has been calibrated according to the data collected in the monitoring process. The research illustrates the variations of the sensible thermal energy demand of the building in different retrofit scenarios, and relates them to the variations of the dynamic thermal properties of the construction components. A parametric simulation study has been performed, encompassing the use of calculation tools and performance metrics at the different scales of the building (envelope-zone-overall building) considering the realistic operating conditions assumed for the initial calibrated model and different climate conditions, typical of the Italian territory and, more in general, of the Southern European and Mediterranean area.

With the growing needs of improving building sustainability, an increasing number of existing buildings need renovation to meet the expectation of the stakeholders. In the pre-design phase, it is very critical to have the best decision made to satisfy both the project budget and the performance standard. For a new buildings, a whole building energy simulation analysis is very helpful for this decision making process because it can provide the stakeholders the evaluation results of all alternative solutions. However, for existing buildings, the as-built data required for the building energy modeling process is not always available, and its manual collection process is time-consuming and error prone. This paper first reviews the state-of-the-art methods of automated data collection, and then introduces the automatic as-built BIM model creation process through a case study. This study also successfully demonstrated the interoperability between the created as-built model and a typical energy simulation tool. At last, a discussion is made about the limitations and challenges of the current state of practice to enlighten the future direction.

The built environment must adapt to a rapidly changing context and, since buildings have relatively long lives, this must primarily be achieved through retrofitting the existing building stock rather than by replacing it. We therefore need robust approaches to evaluating the cost-effectiveness of retrofit investments.Some guidance for performing investment appraisals of building retrofit proposals is available for specific types of retrofit, for example, the economic evaluation procedure for energy systems in buildings in the form of the EN 15459 standard. In this preliminary study, three existing evaluation methods are reviewed and compared. On this basis, recommendations for the development of a robust, general approach to the financial and economic evaluation of building retrofits are made.

Retrofitting of existing buildings offers significant opportunities for improving occupants’ comfort and well-being, reducing global energy consumption and greenhouse gas emissions. This is being considered as one of the main approaches to achieve sustainability in the built environment at relatively low cost and high uptake rates. Although a wide range of retrofit technologies is readily available, methods to identify the most suitable set of retrofit actions for particular projects are still a major technical and methodological challenge. This paper presents a multi-objective optimization model using genetic algorithm (GA) and artificial neural network (ANN) to quantitatively assess technology choices in a building retrofit project. This model combines the rapidity of evaluation of ANNs with the optimization power of GAs. A school building is used as a case study to demonstrate the practicability of the proposed approach and highlight potential problems that may arise. The study starts with the individual optimization of objective functions focusing on building's characteristics and performance: energy consumption, retrofit cost, and thermal discomfort hours. Then a multi-objective optimization model is developed to study the interaction between these conflicting objectives and assess their trade-offs.