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Abstract:The recast of the energy performance of buildings directive (EPBD) describes a comparative methodological framework to promote energy efficiency and establish minimum energy performance requirements in buildings at the lowest costs. The aim of the cost-optimal methodology is to foster the achievement of nearly zero energy buildings (nZEBs), the new target for all new buildings by 2020, characterized by a high performance with a low energy requirement almost covered by renewable sources. The paper presents the results of the application of the cost-optimal methodology in two existing buildings located in the Mediterranean area. These buildings are a kindergarten and a nursery school that differ in construction period, materials and systems. Several combinations of measures have been applied to derive cost-effective efficient solutions for retrofitting. The cost-optimal level has been identified for each building and the best performing solutions have been selected considering both a financial and a macroeconomic analysis. The results illustrate the suitability of the methodology to assess cost-optimality and energy efficiency in school building refurbishment. The research shows the variants providing the most cost-effective balance between costs and energy saving. The cost-optimal solution reduces primary energy consumption by 85% and gas emissions by 82%-83% in each reference building.

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Abstract:Finding the most appropriate configuration of building components at the design stage can reduce energy consumption in new buildings. This study aims to optimize the design of the envelope of a new residential building located in a warm climate (southern Italy). The thermal behaviour of the building has been analysed to evaluate the indoor operative air temperature for several configurations. The building prototype has been modelled using the dynamic simulation software TRNSYS 17 (A transient system simulation program, University of Wisconsin, Solar Energy Laboratory, USA, 2010) using a sequential search technique. Starting from the simplest building configuration, the main evaluated components are: walls, slab-on-ground floor, roof, shading, windows and internal heat loads. For each of these components, different design options have been modelled and compared in terms of indoor thermal comfort. Comfort parameters have also been taken into account to evaluate users' satisfaction with the optimized configurations. The study of the operative air temperature demonstrates that the absence of insulating layers in the ground floor ensures a lower internal temperature in summer. The paper shows how each component impacts the thermal behaviour of the whole building. It highlights the usefulness of the envelope design optimization that is characterized by high values of heat storage capacity, enabling internal temperature fluctuations to be kept under control, especially during summer.Keywords: envelope; optimization; building; TRNSYS; operative air temperature; warm climate; comfort HIGHLIGHTS:•The envelope design of a residential building has been optimized for a warm climate.• Several envelope design options have been evaluated and compared.• Walls with a high internal areal heat capacity are preferable in a warm climate. •The absence of insulating layers on slab-on-ground floor provides lower temperature in summer.• Low emissivity glass and low solar absorbance roof reduce heat loads.

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The European Energy Performance of Buildings Directive (EPBD) recast proposes, a comparative methodology to calculate cost-optimal levels of minimum energy performance requirements for buildings. This paper presents a method able to select the best retrofit action for lighting system, selectively analysing the daylight conditions and applying the cost-optimal methodology for different scenarios proposed for two existing educational buildings located in Italy. With the aim to improve both energy efficient and visual comfort conditions, the retrofit scenarios include lighting solutions with different combinations. They consider the replacement of lamps with more efficient lighting sources and the application of lighting control

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