**1. Introduction**

The shift of attention in the design choices derives from the interpretative evolution of the environmental problem and from the new intervention approach: from an *ex post* impact assessment, with the aim of limiting the damage and environmental risks of already existing works and processes, to an *ex ante*, through prevention and research of concepts and strategies aimed at analyzing a building and its parts upstream of the construction process, with the aim of designing an eco-efficient or low environmental impact system. This is a different approach from the practice that has characterized the building industry in recent decades, particularly attentive to a complex and at the same time delicate "environmental system," often exploited to the limit and erroneously considered unalterable: the changes undergone by the ecosystem are known, as a result of human actions, and the visible repercussions caused by these transformations, such as global warming, climate change, soil acidification, water eutrophication, and depletion of the ozone layer. Architecture does not remain

extraneous to this framework of problems: it is a manifestation of human activities. Therefore, designing and building according to the criteria of sustainability essentially means dealing with the principles that make the balance between use of resources and environmental impact feasible.

Ecologically responsible design has been acquired in many scientific-disciplinary sectors of architecture and is currently the subject of studies and research by the scientific sector of architectural technology and the building production sector. In these areas, two distinct aspects of the problem are considered in particular: on the one hand, the definition of environmental design strategies for buildings and settlements, and on the other hand, the environmental impacts of building products and of buildings as a whole in order to guide the strategies design them. There is therefore a change of hierarchy between the paradigms of the project, which must be rethought and calibrated on new bases and scenarios of a vision over time of the life of the built artifact. The theme is not only the design of the building, but also of the life of a building, in which the temporal and spatial dimensions are fundamental and must be declined on the different scales of the built environment. The role of duration and maintenance scheduling in buildings is decisive on the life cycle from the early stages of the project; they are aspects closely linked to the technologies used, which in turn are consequences of the environmental context: which technology for which duration? Which technology for which context?

To support the ongoing renewal of the design process, Life Cycle Thinking (LCT) is a criterion through which it is possible to carry out actions or make decisions with awareness of the entire life cycle of the building, the process, and the product in question. It can be defined as a current of thought that compares a product or a process to a living organism, which is born, grows, dies [1]. Through this similarity, the life of a building and its process can be considered as a sequence of phases: that of design, that of extraction and processing of raw materials, that of packaging and distribution to final uses, that of construction and system of individual components, that of use and management and, last but not least, the end-of-life phase, which can be transformed into the first phase of new forms of life, through reuse and recycling. The life cycle of an organism or a process interacts with the surrounding environment, and the interaction with adjacent systems can be assimilated to a chain of flows with inputs (substances for processing, energy, human work, technology, money, etc.) and output (waste substances from processing, energy from network losses, waste materials, etc.), in close contact and exchange with the environmental, social, and economic spheres.

For the construction sector, this approach takes root and is accepted with the delay in the implementation of innovation typical of the sector. The need to evaluate the characteristics of building materials first emerges, then the LCT is implemented by the production chain, and slowly and, often, with actions that are not yet well defined methodologically, the approach to analyzing the life cycle of systems is recognized constructive and buildings as the only viable way to understand the wealth of problems that pervade the design of the eco-efficient building. We can state that many companies, in particular those aware of their harmful load on the environment, are moving (since the seventies), also under the obligation of international agreements on the reduction of environmental impacts, to pursue objectives of a more controlled production; others are moving toward the proposal of more or less "green" products and components, whose effective eco-efficiency must in any case be verified beyond the production phase, once inserted in a building context. But this is not enough, clear guidelines toward higher environmental goals and techniques for the prevention of environmental pollution are still faltering, many attitudes are only palliatives, with an unconscious still destructive

#### *Life Cycle Assessment in Architecture as Decisional Tool in the Design Stage DOI: http://dx.doi.org/10.5772/intechopen.112011*

and short-term perspective. Efforts in developing eco-efficiency assessment methods for buildings are appreciable, but still too fragmented and ineffective.

The analysis of the life cycle of an entire building presupposes the decomposition into underestimations of the components that constitute it. This operation may appear simple, but it must be recognized that on an operational level it becomes a very complex practice, due to the innumerable amount of information that the many actors involved in the project must provide simultaneously. A possible approach consists in assimilating building components as industrial products, since they are made in manufacturing industries and, only later, delivered to the construction site and assembled as pieces of an industrial product [2]. This affirmation presupposes a way of building with dry assembly technologies, therefore of combining industrial products, but it could also be traced back to traditional shipyards. A building, built with traditional or advanced technologies, is in any case a complex system, whose variables are not always predictable and controllable like an industrial product; it is a system that must also include esthetic, functional, and social aspects. The environmental assessment of a building must not be reduced to the sum of the environmental impacts of the individual components, since a building is not a car which, once built, can be delivered anywhere in the world and works; the building is built in a precise context and the technical and construction choices determine its duration (prolonged over time compared to other everyday objects we have), which also varies according to the user and the weather conditions with which it lives.

Among the many methods of analyzing environmental quality at different scales of the built environment, the Life Cycle Assessment (LCA) environmental assessment methodology is the reference for the detailed and objective quantification of the environmental impacts of a product and of the building along the entire cycle of life, through the quantification of incoming material and energy flows and outgoing polluting emissions in the phases of extraction of raw materials, transport, production, installation, use and management, decommissioning and end of life. The LCA methodology takes into consideration all types of impact in a complete framework of indicators and all phases of the life cycle, up to closing the cycle in the case of recycling at the end of its life, with the balance of the advantages of avoiding further consumption of materials and energy. The LCA assessment, structured in phases, in addition to the definition of the objectives of its application and of the object to be analyzed, provides for an accurate inventory of all the processes of the life cycle of the analyzed product, which translates into a flow diagram with the quantification of matter, water, incoming energy and outgoing emissions of substances into the air, water, and soil. The latter are translated, through a characterization, into environmental impacts (greenhouse effect, thinning of the ozone layer, etc.) and subsequently evaluated, with a score that indicates the severity of the damage, in order to contextualize the environmental damage to a specific reality territorial.

It is therefore necessary that, in addition to understanding the environmental problem, metabolizing the principles of design aimed at the life cycle, strategies and methods are structured aimed at optimizing the sustainable project first and then the eco-efficient architectural product.
