Abstract
Nowadays, it is of common knowledge that the major share of the European energy consumption takes origin from the building sector. In this context, the European Union has issued a series of regulations and directives in order to outline a common strategy to evaluate and improve the energy performance of buildings, decreasing both the energy demand and greenhouse emissions. These European regulations have been adopted by the Member States, including Italy, and transposed into national legislations. In this process facing climate change towards sustainability, public buildings have been identified as models and change drivers for the entire building sector. Good examples from the Public Administration (PA), in fact, are the most effective way to communicate with citizens, sharing best practices aimed at raising awareness.
Among public buildings, schools buildings constitute an important share, considering their peculiar occupants’ target, their role in the community and, finally, their delicate indoor spaces’ requirements. Focusing on the Italian situation, the educational buildings are about 42,000. However, the 60 % of them were built before 1976, i.e. before the first national law on energy efficiency in buildings. The majority of them need deep energy efficiency requalification plans and consistent interventions, and consequently their performance in terms of energy efficiency and indoor environmental quality is expected to be very poor and inadequate.
One of the biggest barrier to face for an energy requalification of the public buildings’ asset is its consistent sample size, along with an overall lack of Public Administrations’ financing instruments. To meet this latter issue, in the recent years, also thanks to the EU Directives prescriptions, we have assisted to a turn into financing instruments and conventions like the Energy Performance Contract (EPC), which implies the demand of buildings’ energy management to institutions like Energy Service Companies (ESCo). In this way, public authorities can benefit from encouraging mortgages for certified energy efficient renovations through public-private partnerships, thus reducing the perceived risk of the investments. This strategy has allowed overcoming the issue of lack of public financial sources, obtaining tangible and long-term improvements, avoiding directly money investments for the Public Administrations.
As mentioned, however, when it comes to elaborating a plan for public buildings’ requalification, both in terms of constructive technologies and management strategies, another primary challenge is their sample size combined with the still current necessity of great and deep renovations. In this scenario, performing a case-by-case energy audit, along with the definition and optimization of Energy Conservation Measures (ECMs), would represent an ambitious, time and cost-spending perspective. For this reason, there is the need to develop easy and effective tools to analyze and enhance the performance of large stocks of buildings. In this process, reference buildings, as introduced in the EU directives, gain increasing importance, being the starting model for the estimation of primary energy needs and for the assessment of retrofit interventions to be extended to the entire stock.
Besides technological aspects and management strategies, human-influenced factors are pivotal if considering a building as a whole entity. The legislation contemplate occupants quite marginally, nonetheless they have a key dual role in indoor environments. On the one hand, as passive users, occupants are exposed to the indoor space they are in: any retrofit action towards the building has a consequent effect on the perceived and actual indoor environmental conditions and, thus, on comfort and wellbeing. On the other side, as active users, occupants may react to the indoor conditions and interact with the building, affecting its performance in terms of energy and operational processes. In this context, it is important to ensure that energy conservation measures do not affect negatively Indoor Environmental Quality (IEQ) aspects: the risk is that, with the new strict prescriptions and goals towards energy efficiency, and with the demanding of energy management to external companies, the indoor comfort is inadequate and forces the occupants to increase the consumptions in order to enhance their conditions.
The aim of the proposed work is to highlight the main aspects that play a significant role on building’s energy performance and requalification, while ensuring indoor environmental quality conditions. In this perspective, the work has been structured into two sections.
1. Energy performance in school buildings. In this part of the work, the final objective is to elaborate and validate a new effective and integrated method for performing the energy audit of large stocks of existing buildings, avoiding case-by-case analyses, and focusing on identifying the most significant retrofit areas and priorities of intervention. This approach, based on the combination of different data mining techniques (i.e., wrapper feature selection, random forests, hierarchical and k-medoids clustering), is meant to deliver a useful tool for the existing buildings’ stock to professionals and Public Administrations.
2. Indoor environmental quality and occupants' attitudes in school buildings. In this part, a selected reference building has been considered to perform the assessment of the indoor environmental quality conditions and to grasp the attitudes and dynamics of users towards the indoor environment. In this perspective, survey field campaigns have been carried out, focusing mainly on the elaboration of a reliable and structured methodology. Objective and subjective field campaigns have been conducted, in order to grasp not only comfort conditions, but considering also all the behavioural and attitudinal aspects which can lead to the identification of better management and retrofit strategies.
The final goal is to identify the most significant variables and aspects involved in a building, taking into account both building-related and human-influenced factors. In this perspective, the main findings of this work consist in:
1. Elaboration of an easy and quick tool for professionals and Public Administrations useful to analyze simultaneously a large stock of buildings, avoiding a case-by-case approach. The methodology allows to perform energy and descriptive analyses, to group similar buildings according to their main features and to point out anomalies and outliers, to find the best energy conservation solutions and to give a priority of interventions among the selected ECMs.
2. Elaboration of an approach for assessing indoor environmental quality in school buildings. This approach consists in monitoring campaigns of the main microclimatic parameters in the indoor environment and, on the other hand, on the elaboration of subjective survey questionnaires. The methodology allows evaluating indoor environmental quality conditions with an attempt to grasp users' dynamics and attitudes in indoor environment.