Reference buildings for cost optimal analysis: Method of definition and application Stefano Paolo Corgnati a,⇑ , Enrico Fabrizio b , Marco Filippi a , Valentina Monetti a a Dipartimento di Energia (DENERG), Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy b Dipartimento di Economia e Ingegneria Agraria, Forestale e Ambientale (DEIAFA), Università degli Studi di Torino, Via Leonardo da Vinci 44, 10095 Grugliasco (TO), Italy highlights " We analyze the problem of reference building models for cost optimal analysis. " We present the international state of the art on reference buildings. " Three methodologies to define a reference building models (example, real and theoretical). " We present the energy performance of an Italian office reference building model. article info Article history: Received 22 March 2012 Received in revised form 1 June 2012 Accepted 1 June 2012 Available online 26 July 2012 Keywords: Reference buildings Nearly zero energy building Cost optimal analysis Energy performance Office building abstract The Energy Performance of Buildings Directive (EPBD recast, 2010/31/EU) requires Member States to define minimum requirements of energy performance of buildings and building components with a view to achieving cost-optimal levels. In order to calculate the cost optimal level of minimum energy perfor- mance, Member States are required to create a set of reference buildings, at national or regional level, to be used in the calculations. This paper introduces to the concept of reference buildings and to the state of art at an international level. In particular, a general methodology for the creation of reference buildings is illustrated. A case study of an office building as a reference building for the Italian existing building stock is then shown. The process concerning the building definition and modeling was carried out by means of dynamic energy simulation program EnergyPlus. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Building sector is responsible for 40% of the total energy con- sumption at European level. In order to have a practical impact on the reduction of building energy consumptions, the Energy Performance of Buildings Direc- tive (EPBD recast, 2010/31/EU) [1] requires Member States (MSs) to define minimum requirements of energy performance of buildings and buildings components with a view to achieving cost-optimal levels using a comparative methodology framework. Since it is not possible to calculate the cost-optimality for every single building, the comparative framework illustrated in the accompanying Guidelines [2] of the EPBD requires of MSs to define a set of reference buildings (RBs), as typical national or regional buildings. Due to the EPBD request, RBs have hence become a cru- cial topic for studies assessing the energy performance. In particu- lar two recent projects within the ‘‘Intelligent Energy Europe’’ program (IEE), TABULA [3] and ASIEPI [4], holds a reference posi- tion with regard to the definition of typical residential buildings. In the past, many studies pursed the definition of typical build- ings but with different final targets. While some works were aimed to the creation of representative buildings to be used for the eval- uation of energy saving possibilities in existing dwellings [5–7] others pursued the definition of typical buildings in order to devel- op benchmark energy consumption of certain categories of build- ings [8–11]. At international level one of the largest database of benchmark building models for commercial buildings is the one of the Depart- ment of Energy (DOE) of United States, where RB models are defined for 16 building typologies across 16 locations (representative of US climate zones) and three construction periods (pre-1980, post- 1980, new buildings). The EPBD establishes also a strong step forward into the eco- nomic evaluations. Before referring to the cost-optimality method- ology, energy saving measures were often compared by taking into account only the energy consumption and neglecting the economic evaluation. Recently economic evaluations made use of the life cost analysis [12] as well as through the total net present value in a 0306-2619/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apenergy.2012.06.001 ⇑ Corresponding author. Tel.: +39 011 0904507; fax: +39 011 0904499. E-mail address: stefano.corgnati@polito.it (S.P. Corgnati). Applied Energy 102 (2013) 983–993 Contents lists available at SciVerse ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy