Energy efficiency is today no longer just a question of money, but instead a way to reduce the emissions of greenhouse-gases, commonly held to be responsible for global warming [1
]. According to the statistics, buildings account for about 25%, 23%, and 26% of, respectively, Europe’s, Portugal’s, and Italy’s primary energy use [2
], and although the housing sector should be blamed for that, it is up to the public realm to set a good example.
As per the plan “202020”, introduced by the 2009/29/CE Directive [3
], primary energy use and CO2 emissions shall be reduced by 20% within 2020. To this end, the 2010/31/EU Directive [4
], the recast of the original EPBD, introduced the so-called Nearly Zero Energy Building (“nZEB”) concept; unlike Zero Energy Buildings (“ZEBs”) and Plus Energy Buildings (“PEBs”), nZEBs are grid-connected, “high performance buildings, whose low amount of required energy is extensively supplied by renewable energy sources” [5
]. Newly designed public buildings must be nZEBs starting from 01/01/2019, while private developments from 01/01/2021 onwards only.
In spite of this, the nZEB is more of a regulatory concept; it was up to each country to come up with a suitable definition [5
], which has normally been encompassed within the national energy labelling framework [7
]. In Italy, according to the Law n°90/2013 and its Implementing Decrees (Date of issue: 26th of June 2015), a nZEB must comply with very high requirements (as far as envelope and HVAC systems are concerned) and cover at least 50% of its energy and DHW demand with on-site renewable energy sources. The Laws n°118/2013 and n°250/2015 make similar provisions in Portugal. It is no operative tool and it cannot yield, therefore, any qualitative guideline. Voluntary rating systems [8
], such as PassivHaus [9
] and LEED [16
], were introduced long before the nZEB, in 1988 and 1998, respectively. The latter is based on credits; it was conceived in the USA, but has eventually caught on in Europe. The former, which unlike LEED, is based on performance evaluation, was developed in Central Europe and later adapted to other climate zones, either colder or warmer, thanks to institutional efforts (EU’s C.E.P.H.E.U.S. project, [17
]) as well. Nonetheless, climate change and heat waves, which occur nowadays at an alarming rate [18
] and whose effects we are now beginning to experience, force us to reconsider the way buildings are designed. Otherwise, they are inevitably going to suffer from overheating, and require larger HVAC systems to compensate for higher cooling loads even in traditionally cold climates, as anticipated in several studies [10
]. Unfortunately, both labelling and regulatory systems belong in the last steps of the design-process, and have no influence whatsoever on the preliminary stages, when the most influential decisions are made; designers should therefore reject an assessment-oriented attitude in order to embrace a more holistic approach to design, both on the building [21
] and on the urban [22
] scale. Bioclimatic design [23
] should be the stone upon which to build a more systematic approach to design. Although frequently confused with sheer environmental design, it is a century-old discipline, which prefers the context over the concept; bioclimatic constructions are carefully crafted on a case-by-case basis following a well-defined hierarchy, taking advantage of their immediate surroundings in order to reduce their environmental footprint.
Several studies have been concerned about this topic: Soutullo et al. [19
] compared conventional and bioclimatic buildings, Rodriguez-Ubinas et al. [20
] concentrated on the prototypes from Solar Decathlon Europe 2012, while Tzikopoulos et al. [24
], found correlations among the energy indicators of 77 bioclimatic buildings.
In the past decades, the topic of climate-based design for buildings has been widely studied and discussed, up to the importance of having buildings resilient to climatic conditions. Despite this attention, the sheer volume of studies and also the many different directives and national laws issued nationally in the Mediterranean countries have not succeeded in creating clear, shared, and generalizable methodological approaches, useful for guiding the design stage of architects and building engineers.
With this contribution, the Authors wish to show how is possible to obtain remarkable energy performance for Mediterranean buildings, both in winter and summer season, combining traditional construction techniques with automatic regulation and control systems. In particular, this goal is obtained basing the design choices on the possibility of modifying some properties of the building envelope (appropriately managed by building automation control systems) and of bringing accurate dynamic energy simulations into the design process. This approach is applied to a real case study, which is not by chance, a partially underground academic facility in Porto (Portugal), whose only exposed facade—the Southern elevation—acts as the main control device. The building employs some passive solar design features, among which is a considerable amount of thermal mass, which well-justifies a dynamic analysis of heat exchange phenomena.
The last century of human history has taught us that climate change is an issue that we can’t ignore any longer, and that, on the contrary, we must strive to reach sustainability. For some thirty years, following in the footsteps of worldwide and international agreements, far-sighted legislators have been making a difference by calling for energy-efficient constructions and by promoting a shift in the people’s mind-set.
Among other measures, the EU has recently introduced the Nearly Zero Energy Building, or “nZEB”, a regulatory concept, whose proper definition has been left to national regulations. Beside this, however, voluntary systems, based either on performance or rating, have spread all over the place; the result is a very confusing state of affairs, as both systems fail to address the pressing issues that belong in the beginning of the design process.
Bioclimatic design, instead, looks at the subject from a different perspective; a context-based building, the result of an empirical expertise, takes advantage of the local environment, making do without complicated mechanical systems and relying instead on passive design. While frequently associated with low-tech construction or emergency architecture, this kind of design can indeed benefit from the integration with state-of-the-art technology, such as Building Automation Control Systems. This approach has been employed in the design of the new wing of Porto’s School of Architecture; it comes in the shape of a partially underground building, which houses a new canteen, a study room and a parking lot. The energy simulation of this case-study building confirmed the previous assumption, as remarkable improvements in terms of indoor thermal comfort and energy end-use were achieved as soon as building automation was introduced.
The process reported in this paper, which introduces building automation and energy simulation into bioclimatic architectural design, can be scaled and repeated indefinitely, regardless of building size or type. In conclusion, it constitutes an important precedent to look to for any designer of energy-efficient buildings.
In order not to be distracted, some less relevant topics had to be disregarded; as such, they can be considered the starting point for further investigations. These include the optimization of the envelope assemblies, the effect of thermal bridges and that of ventilated thermal mass. As far as IEQ is concerned, CO2 levels shall be taken into account when it comes to natural ventilation; this, in turn, needs to be supported by mechanical systems in order to provide a steady ACH. Moreover, on-site energy generation must be investigated, in order to determine whether the building achieves an nZEB condition or not.