Alessandro Prada

Analysis and improvement of the representativeness of EN ISO 15927-4 reference years for building energy simulation

Representativeness of weather inputs is crucial to limit the global uncertainty of building energy simulation results. The length of the multi-year weather data series and the methodology used for the typical month selection largely influence the results of the reference year development process. In this work, we investigate two possible modifications to the EN ISO 15927-4:2005 procedure aimed at improving the representativeness of reference year heating and cooling needs. The first modification maintains the reference years independent of their final use while the second one leads to the development of specific weather files for heating or cooling analyses by introducing weighting coefficients for the different weather parameters. The study is performed for five North Italy localities with 10 or less years in the data-set and for a sample of 48 simplified buildings. Both proposed modifications brought improvements to the representativeness of the reference year results.

Multi-objective optimization for existing buildings retrofitting under government subsidization

The refurbishment of existing buildings allows remarkable improvements in energy performance, even by mature and off‐the‐shelf technologies. However, the pursuit of nearly zero energy buildings in renovation can lead to non-optimal solutions in terms of comfort. Besides, the initial cost can limit the owner in refurbishing buildings or drive the choice toward energy-efficiency measures with minimum initial cost at the expense of energy and non-energy performances. In this regard, financial incentives can be a key driver to stimulate renovation, mobilizing private investments and overcoming the high upfront costs and relatively long pay-back time of the retrofit. In the literature, the real effectiveness of incentives to improve both the comfort and the energy performance of the cost-optimal solutions has not been assessed in depth. This work investigates to which extent the incentives on different typologies of energy-efficiency measures can improve the performance of the optimal retrofits solutions. The analysis has been carried out on a set of different residential building modules, representative of different building typologies and Italian construction periods, located in two different climatic contexts representative of Italy, mixed-humid (Milano) and warm-marine (Messina) (ASHRAE 2007), optimizing the energy, costs, and indoor thermal comfort aspects.

Analysis of the energy and economic impact of cost-optimal buildings refurbishment on district heating systems

This article aims to define the energy and economic performance of district heating considering the impact of cost-optimal refurbishment solutions of the connected buildings. The possibility to shift to low-temperature district heating is considered as a feasible solution to compensate for the loss of performance of the network in combination with a systematic approach to the refurbishment of the connected buildings. For this purpose, an integrated model for both buildings and network has been developed. Several refurbishment measures for the existing buildings have been investigated, and a multi-objective (energy and economic) optimization has been conducted, by means of a genetic algorithm to reduce the computational time. The results highlight that building refurbishment strongly influences both the energy and economic performance of the district heating system. The distribution efficiency is considerably low during summer—only domestic hot water need—and when a high number of refurbished buildings is considered in the district heating network. Nevertheless, the implementation of the minimum network temperature allows partial compensation for both the energy and economic losses deriving from the refurbishment. Although an incentive to promote the use of heat at lower temperature has been considered, the economic loss deriving from the incentive could not be paid back.

The Calibration Process of Building Energy Models

The importance of model calibration has been growing up as a result of the energy refurbishment policy promoted by the recast Energy Performance of Buildings Directive (EPBD 2010/31/EU). In fact, with the purpose of ensuring a suitable refurbishment design with effective energy conservation measures (ECM), an accurate model has to be defined in order to assess the energy behaviour of the as-built building. In this chapter, some issues related to the model calibration are presented, starting from the definition of an operative procedure step by step. Furthermore, for the most critical phases of the procedure, analysis techniques and experimental methods are described both through theory and practical examples. Finally, throughout the chapter, the analysis of a case study is presented.

Development of algorithms for building retrofit

Abstract Designing buildings retrofit is not an easy task because a wide selection of energy-efficiency measures are technically available on the market, each of which can be applied to a different extent. In a range of different levels, from policy makers to energy service companies, owners, or conductors, there is a need to find the way to plan interventions, depending on the economic resources available and on some additional performance requisites, such as comfort levels, environmental impact, and so on. This means that some guidance is necessary to decide which would be the most effective combination of retrofit solutions among different packages. In other words, the final goal of a retrofit design is typically the optimization of a set of different aspects, not only the minimization of energy needs, with the consequent reduction of CO 2 emissions, but also the maximization of the economic efficiency, dealing with either subsidies or proper investments, depending on the specific perspective, the preservation or improvement of the indoor environmental quality, and ultimately the long term sustainability of the intervention. On the one hand, most of these goals have a competing nature and optimizing just one of them could compromise the achievement of the others. On the other hand, the analysis of all the possible alternatives of interventions requires the application of techniques able to investigate the entire size of the problem, without excluding some of the possibilities, and to find a trade-off among the objectives, at the same time. The research of the attainment of multiple objectives by means of the exploration of all the possible solutions can be solved applying some mathematical techniques known as multicriteria or multiobjective optimization analysis. In this chapter an overview of different methodologies to deal with multiobjective projects and methods to assist and to define the retrofit interventions is described. The techniques are there, but only research institutions really have demonstrated the capability to implement them. Theres not a lack of algorithms for building retrofit or management, but there is still a lack of dedicated software tools, specifically developed for guiding retrofit decisions and using the most promising algorithms, user-friendly enough to support the designer and decision-maker in defining the best alternatives to be considered. For larger applications, on the other hand, practitioners and energy service companies can find useful support in new entrepreneurship initiatives and start-ups focused on providing calculation and optimization services, with an in-depth knowledge of building physics, economics and finance, and fiscal aspects. High initial investments and entering barriers, both cultural and technical, are overcome thanks to an externalization strategy that can justify the settlement of new companies.