**2. New approaches for environmentally responsible architectural design**

In order to easily understand how it can be designed to protect the environment, a building must be thought of as an ecosystem through which natural resources and

semifinished products, components and systems coexist in a continuous cycle of flows (of matter and energy), within which a series of subsystems regulate the flow of one or more types of resources. It is important to understand that the presence of a building in the environment has a large impact both upstream of the construction, before the operational phase, and downstream, at the end of its life span. Focusing on a building and its potential impacts on the environment, it is necessary to consider the two streams of resource flows: those *upstream*, as inputs for the building ecosystem, and those *downstream*, as those that flow out as output from the ecosystem from it. The flow of resources begins upstream (input) with the entire construction and manufacturing industry sector, with the production of building materials, and continues throughout the life span of the building, in which the objective is to create an environment sustainable and healthy for human well-being and related activities. At the end of its useful life, the building must be considered, right from the design and the choices of construction technologies, as a "mine" of components (output flow), to be modified or transformed, for other new buildings or uses. The law of conservation of the mass of Antoine Lavoisier [3] also applies to the building ecosystem, according to which, over a long period, the resources that have entered will eventually come out, presumably transformed. This transformation from entrance to exit is caused by many mechanical processes or human interventions during the use phase of buildings.

It is therefore essential to know and quantify the flows in order to pursue an economy of resources, materials and energy, through the reduction, reuse, and recycling of input flows for a building. Paying attention to the economy of resources, the designer must know how to choose materials and components, knowing the energy content (nonrenewable or renewable) and the environmental impacts as well as evaluating the application context. It must contemplate the containment of nonrenewable resources in the construction and management of buildings, in which a continuous flow of resources, natural and man-made, is generated in and out of the building itself. The concept of Triple Zero, for example, promotes a "concentrate" of sustainability to be considered in the design of a building or a product: production and materials at 0 km, 0 CO2 emissions, reduction to 0 of waste products, and closure of cycles.

The three strategies contemplated by the principle of resource economy are energy saving, water saving, and material conservation; each focuses on a particular resource needed for building construction and management (**Figures 1**–**3**).

In order to optimize the flows in the various phases of the building process in the design phase, Life Cycle Design (LCD) suggests a methodology for analyzing the construction process and its environmental impact, phase by phase. The same sequence is necessary to operate the inventory of the substances involved (input and output) in the production processes involved in each phase of the life cycle, the initial investigation level of the Life Cycle Assessment methodology, a fundamental part of the LCD thanks to which it is possible to extrapolate the data and information on which to base the environmental impact assessment methods, to be used in the architectural design phase.

The preconstruction phase includes the choice of the site, the design phase, the production processes of materials, and components for the building system up to the delivery on site, excluding the installation. According to the strategy of sustainable design, the environmental consequences generated by the architectural project, the orientation, and the impact on the landscape and that of the materials used are examined. The procurement of building materials also generates an impact on the environment: the harvesting of trees could generate deforestation; the extraction of mineral

#### **Figure 1.**

*Conceptual scheme for a life cycle design (LCD) and for the prevention of environmental pollution in architecture.*

#### **Figure 2.**

*The flows of substances in input and output in the "ecosystem" of the building.*

resources (iron for steel, bauxite for aluminum, sand, gravel, and limestone for cement) cause, in addition to a great visual impact, the erosion of entire mountains or chasms and disturb stability soils, as well as generating acoustic and atmospheric pollution (e.g. fine dust); even the transport of these materials can be a highly polluting activity, depending on the weight and distance from the site. The manufacturing phase of construction products requires large quantities of energy, so much so that in many situations it is highly energy consuming and polluting compared to the energy required by buildings for their air conditioning during use: for example, the steel production chains and aluminum require a high level of energy, for smelting at high temperatures.

The construction phase and the operational phase refer to the phase of the life cycle, in which the building has been physically built and is in use and management.

**Figure 3.** *A sustainable building life cycle.*

In the eco-efficient design strategy, the operating methods of the construction and management processes must be investigated in the design phase in order to identify technical, plant, and operational solutions aimed at reducing the consumption of resources. In the investigation of this phase, the possible long-term effects of the built environment on the health of its users are also considered. Works that could significantly contribute to the reduction of the energy demand in this phase are the rehabilitation of the existing envelopes, a more adequate design of the envelopes in new buildings, a regulation of the summer air conditioning, the introduction of automated management systems and a use, where possible of renewable energies. The restoration of the envelopes allows the reduction of consumption for heating and is a binding condition for the installation of summer air conditioning. The post-consumer, or end-of-life, phase begins when a building's useful life has ended. In this phase, the building materials, demolished or preferably disassembled, are transformed into resources for other buildings or waste to be returned to nature. The eco-efficient design strategy focuses on reducing construction waste (which currently includes 60% of solid waste in landfills), reusing systems and components, and recycling building materials.

In addition to the requirements for a sustainable project and the characteristics of a sustainable material, the performance of a technological system, of a sustainable construction site, established starting from 1999 according to Agenda 21—CIB on Sustainable Construction, must be evaluated, which consist of:

• Choice and use of local materials, i.e. a sustainable material, component, or technological system in a specific physical location is not always sustainable in another; the reference to local cultures and ways of use as opposed to the approval of ways of building, as an international style, must be taken into consideration;
