The concept that connects our actions and way of life to the planet's resources is, of course, the ecological footprint.
If we look only at the part of the ecological footprint related to our energy needs—the energy footprint, it can be defined as the amount of territory (land and water) needed to produce a certain amount of energy according to the technology used for its production. The footprint of a person who lives in a city in an industrialized nation far exceeds what is generally perceived; it extends far beyond the space that we "believe" we occupy and is influenced by the quantity and quality of the flows of matter and energy that accompany our daily lives.
Taking our cue from these considerations, our attitude toward consumption should change. This attitude, expressed in different scales and different contexts, should open up the possibility of treating energy as a concrete design variable that can interact with the forms of space and settlements that we design—or, to go straight to the heart of the matter, which we redesign.
In the field of architecture, it is a question of finding appropriate ways to use technologies to produce energy where it is consumed; in other words to create dialogue between the form of energy and the forms of buildings and cities. Photovoltaic technology is, among the different energy technologies, the one that best suits this purpose because of its ability to replace traditional building components; but its use in contexts that are not "of value" —at least in historic or consolidated urban contexts—is still regarded with suspicion and some prejudice.
This attitude reveals a design culture that still conceptualizes according to traditional categories (ie, "of value", historic), without accounting for the need to conceive our cities and habitats in terms of new ones (such as sustainable/unsustainable, producer/consumer) which point to the possibility of evolving positively, to become self-sustaining.
To stimulate thinking about this topic, we present two examples of the use of photovoltaics in existing contexts; although they are very different from one another they are, in our opinion, both very successful. We present them as tangible responses to an issue that is sometimes approached in a defeatist way as if there were no possible solution.
The first example is the adaptive reuse of a tabià—a building used as a stable or barn which characterize the agricultural and pastoral architecture of the Selva di Cadore valley in an area of the Dolomites classified as a Unesco World Heritage site. The project is by EXiT Architetti Associati. The second example, by NettiArchitetti, is the renewal of a facade of a hotel, the Hotel Leon d'Oro, in the center of the city of Bari.
In Selva di Cadore (Belluno), a tabià was transformed into an energy self-sufficient home thanks to a series of photovoltaic modules supplying heat, hot water, cooking systems and other electrical appliances.
It was a challenge because PV is generally perceived as invasive regarding contexts "of value" or even in terms of the popular image of a place. This perception, which becomes a preconceived negative judgment, overlooks the fact that these PV modules both avoid the installation of a diesel system (the usual technology in the valley, which is certainly more environmentally intrusive) and also contribute to containing the energy footprint within the building's physical footprint.
The EXiT project is successful thanks to the attention that the designers payed to the delicate task of replacing the wood of the old roof with photovoltaics, coming up with a solution that is both attentive and "respectful." The starting point was an accurate survey of the building's wooden components and structural joints. Later the building was dismantled; many of the tabià's old beams and boards were recovered and cleaned while other elements were integrated by using similar recovered wood, in order to ensure continuity of colors and materials, and reassembling them.
Particularly significant is the choice not to use photovoltaic components that are "mimetic" of traditional building elements (roof tiles, for example), but rather standard modules, used intelligently, paying special attention to joints, thicknesses and the composition of the different elements. A new exposed steel structure painted black—prepared according to a geometry and a distance between the parts consistent with the size and modularity of the existing tabià—works with the original wood to accommodate the opaque standard photovoltaic modules, and mediating between the existing and the new. 51 modules, each with an area of about 1.63sm and 230Wp, comprise a system with nominal power of nearly 12kWp, occupying overall about 84sm. In one year, it can ensure an output of about 13000kWh, making the home completely energy self-sufficient.
The Bari project is different in context and materials. The project restores the facades of a building constructed in 1972 (designed by Onofrio Mangini) on the corner of the square of the city's central train station.
Despite the differences, it was also a challenge for NettiArchitetti to intervene in a place whose popular image is rooted in the minds of its users and introduce innovative technologies and materials. The designers responded to the challenge with a strategy of integration played out in the careful interpretation of the existing context. In particular, the façade's fiberglass brise-soleil elements were replaced by glass photovoltaic modules, appropriately designed to perfectly replace the screening function of the original structures.
The modules are anchored to a stainless steel frame, structurally connected to the facades by two plates. This structure also accommodates the wiring required to operate the system. The entire system, consisting of the structure and the modules both, was designed so that its connection to the facade reused the existing holes in the reinforced concrete pilasters that distinguish the building.
The modules are semi-transparent, with crystalline silicon cells, distributed across 77% of the glass surface, ensuring the module's shading function. The area of each module is quite large, 2.65sm with nominal power of about 285Wp, while total power is about 24kWp; estimated annual production is about 34000kWh. In this case, the energy produced by photovoltaics is certainly not enough to supply the entire hotel; it covers just over one third of its need but the action is very significant, since electricity use for the hotel industry is ten times greater than housing.
Both projects demonstrate in practice that it is possible to reduce our energy footprint and rescale it according to the spaces we live in, shaping strategies for the integration of renewable technologies that is satisfactory both from an energy-use viewpoint as well as from a formal one. It seems that conditions exist for designers to be able to establish a new aesthetic taking into account these new categories, in particular the producer/consumer relationship.
Tabià / Località Marin / Selva di Cadore (Belluno) / Italia 2010
Project: EXiT Architetti Associati - arch. Francesco Loschi
Energy consulting: Elektroplanung - Per. Ind. Gotthard Baur
Solar panel manufacturer: BAUER Solarenergie GmbH
Hotel Leon d'Oro / piazza Aldo Moro 4 / Bari / Italia 2010
Energy consulting: Tecnomec engineering
Solar panel manufacturer: EPC/Tecnomec Engineering