"I sistemi costruttivi in legno e gli strumenti di valutazione energetico-ambientale. Analisi e armonizzazione degli indicatori di valutazione"

The certification of energy and environmental performance of buildings can be considered as an important decision tool in order to make coherent design choices in terms of the monitoring of the building process as far as the construction site, the sustainability of materials, the overall quality of housing and the investment capital are concerned. In fact, the selection of the materials and the construction systems has a dramatic impact on the embodied energy and carbon dioxide emissions during the building life cycle. The growing awareness about the positive role of sustainability certification in reducing the environmental impact of public and private buildings, together with the need to communicate the energy and environmental characteristics of products suggests that product data sheets will become more important and structured. In such context, the PhD investigation focused on the identification and harmonization of performance indicators which include and consider the use of wood. The interest lays in the fact that wood is one of the most complex building materials due to its renewability (although with a period of 30 years), carbon capture and storage characteristics, making it less impacting on the atmosphere during life cycle, depending on the end-of-life scenario considered. The mentioned performance indicators are generally categorized into protocols. These “environmental assessment tools” list, weight and combine the different indicators to produce one final rating. In this regards the following protocols have been considered the English BREEAM, the first to appear and one of the most adopted internationally together with the American LEED; the Japanese CASBEE developed for high seismicity context; the Italian Protocollo ITACA; and the recent Italian version of the American LEED. As a result, the identification and analysis of the wood assessment criteria led to some interesting observations. Their role and weight in relation to the maximum final score in each assessment tool changes quite remarkably, for instance, the incidence of wood ranges from 22% to 41% from one tool to another and, even more interestingly, the incidence of criteria specifically designed to account for wood, when present, is generally around 1% or less. Also, the proposed harmonization of the indicators led to the identification of: - analogies and differences among the selected assessment tools; - physicochemical, technical, logistic and environmental impact information needed to carry out an environmental evaluation; - indicators to assess the renovation and demolition phase of buildings; - the contents of a hypothetical "environmental data sheet" of wooden products (or other construction materials); - the introduction of an indicator that takes into account the origin of renewable materials; - the opportunity to make the certification of renewable material mandatory; - a synthetic indicator of the materials LCA (as in BREEAM) in order to make the comparison among materials simpler and more readable. The definition of a set of standard criteria and indicators directly affects the drafting of material environmental and energy data sheets. The comparison of actual technical data sheets with the proposed set of indicators led to the following observations: - the information contained in the current data sheets is incomplete; - rarely the environmental data sheets show information about energy consumption and environmental impacts during the production phase; - end-of-life scenarios are seldom indicated. Thus, to easily compare the environmental impacts of different materials or components, it is only possible to consider the two most likely available indicators of energy consumption (Embodied Energy) and carbon emission (Embodied Carbon). In the building industry, the wooden products reach different levels of environmental impact because of the use of specific glues and mechanical processing that affect the environmental footprint during the production phase. The environmental assessment of buildings, however, not only depends on the used materials and components, but also on the technical and building characteristics of the adopted construction system. Their strengths and weaknesses were redefined by proposing a qualitative assessment method based on the combined performance filtered by the technological and environmental properties, over the life cycle. The comparison took into consideration the environmental, design and building characteristics of some timber construction systems (i.e. frame, frame construction panels, solid wood panels, log construction and small modular wall elements) through the proposed new set of indicators. This showed that building systems with more design constraints, such as the log construction and the small modular wall elements, have a lower potential score. For the sake of a final verification test, a comparison analysis was done between the Protocollo ITACA, the International Key Performance Indicators by the SB Challenge Conference 2011 and the Set of Harmonized Indicators. This analysis showed that: - it is not always easy to find materials environmental data (i.e. Embodied Energy and Embodied Carbon); - corrective coefficients for materials data standardization, e.g. EE and EC, taken from different databases may be introduced; - it could be useful to introduce energy consumption and CO2 emissions indicators for the building life cycle, not only for the operations and maintenance phase; - harmonizing the performance indicators makes the comparison between different buildings easier. In detail, the comparison between the set of Key Performance Indicators by the 2011 SB Challenge Conference and the Set of Harmonized Indicators showed that the number of indicators needed to carry out an environmental certification was 6 versus 25. The difference in the number of indicators involved was driven by the different aim of each evaluation. The goal of the SB Challenge 2011 Conference was to compare certified buildings rated by different assessment tools while the goal of this investigation was to identify the fundamental data needed to carry out an exhaustive environmental assessment. The harmonization led to an expected increase in the number of indicators related to the material, this fact being well related to the importance that raw materials have in the final environmental assessment, as said The new set of indicators makes the harmonized method very suitable when drawing the global impact analysis in the design phase, as well as a fairly more complex but reliable tool when simply comparing two buildings. Summarizing, the main indicators set for material environmental impact is made by eight numbers which are subdivided: Energy and Pollution category: - Embodied Energy in kWh/m2; - Embodied Carbon in kg CO2/m2. Material category: - Quantity of building materials in t/m2 or kg/m2; - Quantity of renewable materials in t/m2 or kg/m2; - Quantity of materials reuse in t/m2 or kg/m2; - Percentage of environmental certificate materials (respect the complete materials weight); - Percentage of materials with the instruction of dismantlement or recycling. Indoor Environmental Quality category: - VOCs concentration (in ppm, mg/m3 or mg/m2h). From the above subdivision, the CO2 emission indicator is certainly reductive in determining the smaller environmental impact. As such, the use of wood in construction should be driven by its overall life cycle impact, not only by its carbon capture characteristics set alone This research, in conclusion, aimed at pursuing the trend of generalizing and standardizing the evaluation of buildings. That is, to improve the analytic tools, integrating the most relevant effects, including the contributing material factor, not forgetting the different contexts where such an environmental-intensive activity takes place.