Accounting for nearly 40% of final energy consumption, buildings are central to European energy policy. The Directive on Energy Performance of Buildings establishes a benchmarking system known as cost-optimality to set minimum energy performance requirements in new and existing buildings. This paper applies the cost-optimal methodology to an existing structure located in the Mediterranean area (Southern Italy). The building is composed of two units that have been considered for different uses: hotel and multi-residential. Several energy efficiency and renewable measures have been implemented both individually and as part of packages of measures. The cost-optimal solution has been identified as able to optimize energy consumption and costs from financial and macroeconomic perspectives. The first reference building (hotel use) shows a maximum reduction of primary energy and CO2
emission of about 42%, falling within the CasaClima energy class D, while the second reference building (residential use) achieves a value of 88% for primary energy and 85% for CO2
emissions, falling into class B. Thermal dispersions through the envelope can be limited using a suitable combination of insulating materials while a variety of technical variants are selected, such as VRF (variant refrigerant flow) systems, heat pumps with fan coils associated with controlled mechanical ventilation, solar thermal and photovoltaic. This paper illustrates the development of energy retrofit projects, in order to reach a balance between efficiency measures and costs for a building having two different uses, providing guidance to similar case studies related to a warm climate.
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