استفاده از ساختمان های مرجع برای ارزیابی عوامل صرفه جویی انرژی در انبار ساختمان مسکونی: تجربه ای از پروژه TABULA

Retrofit actions applied to the existent building stock aim at increasing the energy performance, considering the optimal trade-off between energy savings and costs, according to the Directive 2010/31/EU. To select effective refurbishment measures and to quantify the energy saving potentials of the existent building stock, the analysis should be performed on “reference buildings”. This article presents a methodology for the identification of reference buildings, according to the IEE-TABULA project (2009–12) aimed at creating a harmonised structure for “European Building Typologies”. Among the possible applications of the building typology, this work focuses on the potentialities of energy savings and CO2 emission reductions for the European residential building stock. In particular, the Italian approach to model the energy balance of a subset of the national building stock is described; the results show the enormous potentialities of energy savings even with basic energy retrofit actions. Cost analyses were not in the scope of the project, but the results of this study are the basis for further investigations aimed at assessing the cost effectiveness of sets of measures. In this regard, the TABULA building-types are being applied by the Italian government for calculating cost-optimal levels of energy performance, complying with the Directive 2010/31/EU objectives.

The interest in the analysis of the energy performance of large existing building stocks is highly increased all over the world. In fact, the most effective way to achieve significant reduction of energy consumptions in the building sector is to improve the energy quality of existing buildings. To do this, it is crucial to assess as clearly as possible the actual energy performance of buildings and, after that, apply suitable retrofit measures, both from a technological and from an economical point of view. Many studies have been carried out on this topic, starting from the knowledge of the condition of the existing building stock (Ravetz, 2008), applying statistical data analysis (Theodoridou et al., 2011a), collecting and organising data (Dascalaki et al., 2010) and identifying methodologies for assessing the building stock energy performance (Fracastoro and Serraino, 2011 and Corgnati et al., 2008). The existing building stock is wide, heterogeneous and composed, for the great amount, of buildings with poor energy characteristics. In Europe, according to Loga et al. (2012) and Dascalaki et al. (2011), a large amount of the existing building stocks in all the Member States show annual energy demands for space heating and domestic hot water ranging between 150 kWh m−2 and 300 kWh m−2. In this scenario, even basic energy retrofit actions may reduce significantly the building energy demand of a large number of buildings (Desideri et al., 2012). Basic actions on a large scale can determine significant energy savings, as stated in several works (Balaras et al., 2007 and Ahern et al., 2013). However, retrofit actions have to be chosen accurately; many studies focus on the identification of the best refurbishment measures to be applied to existing buildings (Brecha et al., 2011 and Roberts, 2008), considering economic viability (Galvin and Sunikka-Blank, 2013 and Ouyang et al., 2009), market and political context influence (Atkinson et al., 2009 and Weiss et al., 2012), societal economic perspective (Joelsson and Gustavsson, 2008), environmental aspects (Ardente et al., 2011), theoretical vs. actual energy consumption (Majcen et al., 2013), and applying systematic methods and tools (Mechri et al., 2010). The interest on this topic raised a lot in Europe in the last years: in particular, the European Directive 2010/31/EU (European Union, 2010) introduced some remarkable concepts to address the energy retrofit measures of existing buildings in the right direction. This Directive introduces the concept of “cost-optimal”, defined as the energy performance that leads to the lowest cost during the estimated economic lifecycle. At the same time, it enlarges the concept from cost optimal to cost effectiveness, as graphically shown in Fig. 1. This concept has to be adopted by the European Member States in order to set energy performance requirements, for new and especially for existing building, “with a view to achieving cost optimal levels”.According to the Commission Delegated Regulation No. 244/2012 (European Commission, 2012a) and to its accompanying Guidelines (European Commission, 2012b), Member States are required to define “reference buildings” that should represent the typical and average building stock in each Member State, in order to obtain general results consistent with the characteristics of the analysed building stock. As a consequence, the “cost optimal analysis” requires the preliminary definition of reference buildings. When these are available, the investigation procedure can include the following steps: 1. energy performance calculation of the reference buildings to assess the baseline of the energy performance; 2. definition of sets of energy retrofit measures to be applied to the reference buildings; 3. energy performance calculations to evaluate the energy performance after the retrofit measures; 4. calculation of the life cycle costs using net present valuation; and 5. finally, assessment of the cost optimal (and cost-effective) set of measures to optimise (and increase) the energy performance of the reference buildings. According to the Commission Guidelines, it is recommended that reference buildings are established in one of the two following ways: (1) selection of a real example, representing the most typical building in a specific category (e.g. type of use and reference occupancy pattern, floor area, compactness of the building expressed as envelope area/volume ratio, building envelope constructions with corresponding U-value, technical systems and energy carriers together with their share of energy use) and (2) creation of a “virtual building” which, for each relevant parameter, includes the most commonly used materials and systems. The choice between these options should depend on expert enquiries and statistical data availability. It is possible to use different approaches for different building categories, to have (real o virtual) reference buildings able to represent the characteristics (geometry, envelope, systems, etc.) of each specific building category. In the following sections, a new procedure to create a harmonised structure for “reference building” definition at European level, according to the goals of the European Project TABULA, is described. The project focused on residential building types and, in this article, the results concerning the Italian reference buildings are presented in detail. In TABULA the building typologies are a basis for analysing the national housing sector ( Loga et al., 2012). The national approach for modelling the energy balance of the residential building stock applied to an Italian region (Piedmont) is described. The energy saving potentials on the existing residential building stock are investigated by applying two sets of retrofit measures (two levels, “standard” and “advanced”, as defined in the TABULA project) to the reference buildings. Moreover, a comparison between different energy balance modelling approaches of some European countries involved in TABULA are shown and the results are compared. The outcomes of this study, focusing on the definition of reference buildings and analysis of retrofit measures, will be the basis of further investigations aimed at assessing cost optimal and energy effective sets of measures.

The definition of “reference buildings” which represent the characteristics of large groups of buildings is a crucial issue, in order to assess the actual energy performances and the energy savings of the building stock, thus to address the national and regional energy policies towards the definition of effective refurbishment measures on the existing buildings. According to the outlines of the TABULA project, a common methodology to define “building typologies” and to create reference “building types” at European level has been introduced and discussed, focusing in particular on “Real Example Buildings” and “archetype” buildings. The “building typology” offers the possibility to supply a wide range of information for individual reference buildings, to assess their importance by projection to the whole stock or to subsets of the stock, and to quantify the potential of energy savings due to refurbishment actions, in this way addressing energy policy at national or local level. The “building typology” can have also other scopes: to be used by consultants for initial energy advice activities in order to provide house owners a quick overview of the energy performance of a building similar to their own; to be used, as a set of example buildings, in software comparison studies or for the evaluation of subsidy programmes; to be applied as an appropriate instrument for housing companies to assess the energy performance of their building portfolio. Among the possible applications of reference buildings, it has been investigated the evaluation of the potentialities of energy savings and CO2 emission reductions from the present state to a renovated state (“standard” and “advanced” retrofits) of the residential building stocks of some European countries. To show the methodology, the Italian approach to carry out the analysis has been presented and applied for modelling the energy balance of the residential building stock of Piedmont region. The performed studies, both at European and national and regional levels, show that the building typologies can be a helpful tool for modelling the energy consumption of the building stocks and for carrying out scenario analysis. The consideration of a set of representative buildings makes it possible to have a detailed view on various packages of measures for the complete building stock or for its subcategories. The usefulness of the reference buildings for scenario analyses and the enormous potentialities of energy savings in existing buildings even with basic energy retrofit actions are revealed. The results of the energy balances developed in the TABULA project show that, on average, more than 40% of energy savings could be obtained by the whole analysed European residential building stock just applying a basic renovation. However, the quality of model calculations depends very much on the availability of statistical data. For reliable scenario analysis, information is necessary about the current state of the building stock and about the current trends. Moreover, information on the actual energy consumption should be made available in order to carry out comparisons with the calculated building energy performance. The availability and regular update of the relevant statistical data will be an important basis for the development and evaluation of national climate protection strategies in the building sector. The results of this study are the basis of further investigations aimed at assessing cost optimality and the cost effectiveness of sets of measures, also taking into account the technical feasibility of refurbishment strategies. In this regard, the Italian outcomes of the TABULA project (building types, construction features and characteristics of the heating systems) are very useful in the development of national and local energy policy and in the set-up of energy performance requirements in compliance with the comparative methodology framework of the European Commission according to the European Directive 2010/31/EU.