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Tradition And Innovation For Energy Self‐Sufficiency Of Mediterranean Traditional Architecture
Fabio Fatiguso DAU – Department of Architecture and Town Planning
Polytechnic of Bari e‐mail f.fatiguso@ poliba.it
Marianna Urso
DAU ‐ Department of Architecture and Town Planning Polytechnic of Bari
e‐mail [email protected]
INTRODUCTION
The consumption of non renewable resources, as well as the tendency toward new approaches with low anthropogenic impact on the ecosystem, has been a major concern for the international scientific and technical community for the last years. The construction field, which is one of the most responsible for the consumption of resources, it has increasingly being asked to focus on the energy efficiency of buildings and on the energy "self‐sufficiency" throughout the service life. The emanation of the European Directive about energetic performances of buildings (2002/91/CE), as well as all the following national dispositions, is a clear evidence of this attention.
Nowadays, the operators are mainly focused on design and construction of plant system components, products and systems for energy saving, and technologies for exploitation of renewable resources applied to new buildings and buildings dating back to the 60’s and 70’s, that are built with “modern” constructional techniques and technologies.
On the contrary, the interest for the traditional historical architecture is limited, probably due to the difficulty to match the improvements required by current standards and regulations with the existing architectural features. Historical buildings are basically unique. As a result, a performance policy has to be addressed in order to enhance, on the one hand, energetic efficiency/saving and self sufficiency and, on the other hand, conservation of historical identity.
Within a research aimed at identifying approaches and methodologies for qualifying energy efficiency of existing historical architectures, the study aims define appropriate for improving energetic performances of buildings. The abovementioned aim will concern the integration of technological solutions and suitable products and the development of prototypes. As a consequence, it will point out tools and tecniques to integrate systems for energy production and renewable resources exploitation, in order to preserve the existing architectural heritage and to reduce the global Energy demand from the buildings, by enhancing their self sufficiency.
All the procedures and solutions will be applied and checked out on a case study, a representative historical town in the Mediterranean area, in order to evaluate their effectiveness, also in terms of benefits, and to generalize the study.
ENERGY EFFICIENCY OF EXISTING BUILDING HERITAGE
For long time, the EU has pointed out as strategic objectives, the introduction of energy efficiency principles in all the human activities and the improvement of renewable sources exploitation. Recently,
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through the White Paper (1) and the Green Paper (2), new guidelines of a common energetic policy have been suggested, as a necessary precondition (along with sustainability and reduction of climatic changes) to endorse competitiveness and security to the future of the European Union.
Among the different human activities, the particular prominence of the construction sector within the compartments with the largest consumption of resources has immediately emerged, with reference both to the realization phase and to the management and operation ones. Specifically, there are numerous studies and applied researches, within the EU RST programmes (JOULE‐THERMIE, INCO, FAIR, ALTENER, SAVE I e SAVE II), focused on the rational use of energy.
More recently further studies have been developed, to enhance investments on energy efficiency and on renewable energy sources for non‐residential and tertiary sector buildings (GreenBuilding (3), EL‐TERTIARY (4)), to propose construction strategies for passive houses in the south of Europe (Passive‐On (5)), and to define technologies and planning approaches to sustainable cooling (KeepCool (6)). The International Energy Agency IEA (7) identifys different scenarios, which show substantial potentials for improvement of energy efficiency in existing buildings. In such scenarios cost effective energy efficiency improvements in buildings play a major role in the reduction of energy consumption.
A study by ECOFYS (8) on Mitigation of CO2 Emission from the Buildings Stock shows that 55 % of the energy reduction and CO2 emissions from buildings in the European Union members can on average be saved just through increasing efficiency in the building envelope.
This study for the European Union calculated the economic least cost optimum for a 30 years lifetime and only measures that are feasible for the owners are included in the estimates. Only savings that can be obtained through improvements of the buildings envelope were included.
In this context a fundamental role is played by the existing buildings, in particular, by the traditional and historical heritage. In fact, it is not acceptable to rule out existing buildings (in Italy about 40%) from the processes of energy efficiency improvement only due to the apparent difficulty of matching the current materials and technology solutions with the specific features of traditional and historical construction.
Moreover, there are only a few European research projects, referred to singular and specific cases though, for example the historical centre of Lisbon (9), the Ancient Ostia area (10), some office buildings in Greece (11). In Great Britain government policies for the refurbishment of historical buildings are under examination (among them, the pilot project for the energy refurbishment of tenements in Glasgow is particularly relevant (12)), while in Germany a pilot project “Low‐Energy Standards for Existing Buildings” (13) about the historical heritage of Berlin is in progress.
Several research projects have been carried out for the integration of renewable sources based systems in refurbishmant of historical contexts, including REBUILD (1993 / '95) (14) and PV ACCEPT (2001/2004) (15), the first is aimed primarily at recovering bioclimatic passive solutions of Traditional Building Heritage, the second, to improve the acceptability of photovoltaics using outdated technology.
OBJECTIVES AND METHODOLOGY OF RESEARCH
Taking into account the previous considerations methodological approaches and appropriate technological solutions are needed for the traditional and historic buildings, in order to combine energy building performances with conservation of historical‐material‐technical‐architectural features, and get to a dynamic conservation for building retrofitting. The peculiar formal, technological and materic features of traditional and historic buildings makes it difficult, and sometimes inappropriate, the translation of living quality in objective standards and the implementation of methods and "current" solutions whose results are not logically related to the overall objectives. This requires, from the one hand, to overcome traditional categories of intervention and specialist disciplinary approaches as a
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guarantee for achieving quality and, from another hand, to get to a model of guidelines for the comprehensive design, able to consider the complexity of elements and relations between those.
Thus, the energy efficiency of traditional and historic building, which is not a 'need for modernity's sake, can be one of the essential means to combine the resolution of functional and technological criticalities and the refurbishment of the original identiity of buildings, with the need to ensure compliance with existing rules and standards and to improve building performance. Moreover, the specific formal and technical attributes of traditional and historical architecture must not be a barrier to the implementation of innovation strategies in the refurbishment, whose role can be established on a new balance between space, materials, new functional and technological elements.
The technical solutions, through products and advanced systems, may respond appropriately to all the performance lacks of buildings built with traditional techniques, which cannot be used anymore for refurbishment purposes. In this case, the intervention quality is substantiated in a "intrinsic quality "of the implemented choices and solutions themselves, and a "relationship quality", referring to the compatibility between the solutions and the buildings.
Specifically, this paper reports on the results (still incomplete, since the study is in progress) about the integration of renewable energy based systems in significant historical and architectural contexts. The search starts from the knowledge of the historical heritage with particular reference to the technological and formal features of building units and bioclimatic inherent principles in the existing traditional heritage. Then, the study develops in an integrated manner, the valuation of the applicative potentialities of solutions and products developed for new buildings and/or other climates, studying application methods and variants for their compatibility with existing components and materials. More specifically, it defines innovative technological devices to produce energy from renewable sources that are compatible with materic, formal and architectonics features of existing buildings. The evaluation of the efficiency of approaches and solutions, through the application to a case study, will verify the effective improvement of the performance qualities and the energy consumption reductions by means of computerized modellings.
PROTOTYPE OF INTEGRATED SYSTEM FOR ENERGY SELF‐SUFFICIENCY: STONE PHOTOVOLTAIC SLAB
The study, following the with European research projects for energy efficiency of traditional and historic building, and aware of critical issues to work in these contexts, about formal and technological building features, aims to integrate renewable energy based new technology into existing heritage.
Specifically, the objective of innovative technological device design is to include criteria of efficiency, solar radiation, shading, in compliance with structure, building envelope and historical and artistic constraints. The prototype, in fact, aimed at overcoming problems found in the whole Mediterranean area about integrated photovoltaic systems installation and walkable roofing level, where stone paving is matter of protection.
The Photovoltaic stone slab (Figg. 1‐2) converts solar energy into electricity respecting building volumetric ratios, because the prototype is designed to provide good aesthetics and high performance technology.
The System develops two techniques, that are widely experienced in construction, composite stone and panels for outdoor use in raised access floor, making it possible to pursue a sustainable design approach. The first one uses recycled material molds that makes it possible to adapt technology to all the different stone typologies used in Mediterranean area construction, while adapting the support to any context and any type of surface, both vertically and horizontally, respecting geometric constraints that each installation presents. The second one instead, ensures high performance in terms of
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ventilation, mechanical strength and maintainability of the system. This technology is also reversibile, very important feature for refurbishment of the historical heritage.
Fig 1. Prototype render Fig 2. Prototype elements
The prototype is composed of a stone slab, designed to meet requirements such as mechanical strength, impermeability, durability and it doesn’t change aesthetic aspect. The size is of 300 x 600 mm, consists of several layers, including a core calcium sulphate fiber reinforced of 25 mm thick, on whose sides are primed retardant plastic edges to ensure waterproof and moisture resistence of the panel. The second layer of 20 mm, glued to the first with adhesives based on aqueous dispersions of special copolymers function as a coating, made of composite natural stone and treated with environmentally friendly solvent‐free curing agent. The surface layer is colored with iron oxides, which ensure a longer life than natural stone. In fact, they are enhanced, during treatment, against acid rain corrosion and UV solar rays. The panel, appropriate for photovoltaic module installation, consists of mixed granulometry stone aggregates and organic polymers, which provide with resistance and high integration with existing pavement, possibly refurbished. The total thickness is 45 mm including stone cladding.
The panel has a set‐off of 436 x 136 x 10 mm, ventilated by four rifts below, measuring 80 x 10 mm, which ventilate the back of the cell, and two cavities, 468 x 164 x 5 mm and 454 x 150 x 5 mm, used for, respectively, placement of protective glass stuck in 4 special collections and photovoltaic module. In order to make connections and to close the electrical circuit two holes (Ø 15) have been provided on the stone slab, to allow the passage of the connectors. For static reasons, set‐off allows that each element transfer the weight on resistant structure and not on the underlying component.
Another component of the prototype is the photovoltaic module covering the surface made of PMMA (polymethylmethacrylate). The thickness of 6 mm is sufficient to obtain a good mechanical strength, improved by metallic ribs that give strength to the element.
The slide is flat and perfectly adherent to the form of set‐off where the couple will enter. For a quick assembly, four protrusions, of 5 x 12 mm suitably shaped, fit together to stone support. The dimensions of 468 x 164 mm, larger than the module, serve to provide protection from atmospheric agents and possible shocks.
The PV module used for converting solar energy into electricity, is designed for maximum performance while providing a reduced module surface, consisting of three polycrystalline silicon cells arranged on a single panel. Specifically the module is provided by tempered solar glass 4 mm thick, two layers of Ethylene Vinyl Acetate (EVA) and a layer of Tedlar, which cover the silicon cells. a process of rolling at 140 ° C generates a unique body resistant and waterproof. Modules come into standard cell size of 156
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x 156 mm, with an efficiency of 15 and 16.4%.
The cables adopted for the prototype are high‐performing, in terms of abrasion resistance, high mechanical stress; they are insulate with e‐beam crosslinking and sheathed; high termic, oil, abrasion, ozone, UV and fire resistence, development of low smoke, halogen free, flame‐retardant, flexible, low footprint, very resistant to mechanical stress, long‐lasting. The technology is specially developed for connecting components of photovoltaic systems inside and outside of buildings and equipment which may occur in high mechanical stresses and extreme weather conditions. Features needed by the time the photovoltaic stone slab prototype is designed to be installed in cover.
To complete the design of the technology, the assessment was performed in a cost‐benefit analysis which have resulted, for the production and installation, in 683 € / m2 cost.
Fig 3. Solar energy plant axonometric projection
The study of photovoltaic slab is designed to ensure maximum versatility, not only of geometric and chromatic features, but also in terms of applications. The prototype allows a basic technology similar to establish a building diverse technological systems that can coexist without causing a visible impact or interfere linked to the different technical requirements. Indeed, the need to integrate technological systems capable of converting solar energy into useful energy, concerns not only the field of photovoltaics, but solar thermal as well. In the latter case, the situation could be even more unfavorable, since the collectors and storage tanks are undoubtedly greater than photovoltaic panels.
To overcome this difficulty a possible variant of the prototype has been suggested (Fig 3). The idea is to change the shape of the support in composite stone and polymers from the set‐off, in order to realize a floor heating that can power the circuit of health, through the use of suitable reservoirs and thermal storage, and integrate a heating low temperature. The application, due to the length of the solar panels, will be provided on size equal to 300 x 1200 mm.
APPLICATION TO CASE STUDY: THE HISTORICAL CENTER OF MOLFETTA
In Italy the “Istituto Centrale di Catalogazione e Documentazione” (Iccd) conducted the National
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historical towns Census, identifying 22,000 units of which 50% originated in medieval times. The already significant number tends to increase by extending the Analysis of Mediterranean region. The case study representative of historical buildings serial to test the validity of the prototype has been identified in the historical town of Molfetta (Italy).
Historical town consists, mainly by building organized into blocks, each comprising a variable number of 20‐30 individual housing units dating back to the medieval period (Figg. 4‐5).
The block type consists of urban dual comb, two sets of cells as opposed to the prevailing primary vertical, pull along the longitudinal direction of development, parallel to the borders freely.
The primary unit is configured in general with the "tower house", each built on multiple levels with independent access to ground floor and a staircase that serves the different levels.
Fig 4. Block 17 plan Fig 5. Case study aerial photography
As far as geometric‐dimensional features of elementary cell is usually formed in a single plant overlooking the street with a reduced front that rarely reaches 7 meters in width, while the depth is defined by the number of rooms. Elevation is distributed over two or three levels above ground, sometimes has a basement with heights between floors of less than 4.5 meters (16).
The main technical and constructive features, however, are represented by a vertical masonry carring skeleton structure, the horizontal closure are vaulting on basement and low ground floor, wood floors upstairs, vertical links with steep stairs to the development predominantly straight, brick floor earth, wood at higher levels, positioned in the orthogonal direction to the windowed front. Typically each floor housing unit consists of a single compartment, with no openings on the ground floor and one window, which is not always aligned with those adjacent, to each of the upper levels.
The horizontal openings misalignment on the various tables point out, inter alia, the different proportion of free floor plans for the various cells adjacent, effect of the constructive autonomy of each unit.
Health conditions are uneasy for low ventilation and lighting, and sanitation and technology lack in general. The case study is the housing unit address in via Forno house number 17‐19, emblematic example of housing and urban context for location and accessibility, but considerations done could be extend to the old town.
In the preliminary step of design and theory application of photovoltaic flooring, it was necessary to make a thorough environmental conditions analysis of the area. The photovoltaic modules are, in fact, under the continuous influence of solar radiation, atmospheric agents and other elements such as dust
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and pollution.
The key factor for the total return of the plant, is represented by solar and sky energy radiation, which is the essential source of power to the system. Best design practice aims to place photovoltaic modules to intercept the maximum solar radiation, in this case the horizontal arrangement was necessary. Another important parameter is operant cell temperature, closely related to radiation and air temperature values, and other factors such as wind speed or support type on which the photovoltaic component is applied .
To examine the mentioned factors above in the old town of Molfetta, it has developed a three‐dimensional computer model, created with the computerized ECOTECT V520, to study in detail the the block and building unit solar exposure.
Examining, in fact, the solar paving radiation at December 22, in which the angle formed by the projection on the plane of the horizon line joining the Sun‐Earth is a minor over the entire year, and at June 22, in where the angle is greater, it was possible to observe how the sun exposure is poor in the late afternoon hours of the months ranging from September to December (Fig 6‐7).
Fig 6. Polar Diagram 22/12 Fig 7. Polar Diagram 22/06
In a first qualitative approach, using the exemplified model of the entire block, marked in orange to distinguish it from the boundary condition, it’s possible to evaluate the shade (the one in the picture (Fig 8) is reported at June 22) and critical points due the offsets on the south‐west altitude, a consequence of the construction autonomy that is typical of the historical town development.
Fig 8. Shadow Model at June 22
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Using the same computer support (ECOTECT) it is impossible to quantify accurately the incident solar radiation intensity on a surface of the model, specifically, we got the figures relating to the flat roof of the dwelling in via Forno n. 17‐19.
The numerical value about Avg Daily total (Wh / m²), information on total daily average solar energy hitting the surface coverage, is equal to 3276.157, 1658.052 in Wh / m² is the value of Avg Daily Direct and Diffuse is 1618.105 Wh / m² (Fig 9).
The cumulative insolation Analysis is necessary to correctly position of stone photovoltaic slabs roof, so it manages to capture the maximum amount of solar radiation throughout the year.
Fig 9. Solare exposure via Forno n. 17‐19
The computerized simulation permits to estimate, known the incident solar radiation value, the annual electricity production of photovoltaic devices. The survey is more accurate, considering the pv module surface material type and energy efficiency, in the specific case of the prototype, the modules efficiency is equal to 16%.
Energy production of the roof is of 2233.8 kWh. The same data can also be read on the chart below (Fig 10).
Fig 10. Electricity energy production Roof covering
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Further to the solar analysis and showing advantage to building energy performance of partial photovoltaic paving, 105 solar stone slabs have been provided, with east‐west, measuring 60 x 30 cm able to ensure the most efficient coverage. In order to avoid a partial shading of the modules, the actual module surface area is reduced to 18.78 m2.
The photovoltaic slab surface is not centered within the entire coverage area: the reason for this choice is related to the boundary situation of the building unit that has, on the south side, buildings with a maximum height above 10.80 m, favoring a greater roof shading in the cold months. The overall energy efficiency achieved is equal to 1.26 kWp, but could be increased, assuming a system that works differently in warmer months and during the afternoon of cold ones. Indeed, we can install a larger number of slabs, equivalent to 15 pieces for an increase of 200 kWp. Such intervention should be further investigated for effective assessment of feasibility.
The Image below (Figg. 11‐12) is an overview of the roof covering, being able to evaluate the visual and aesthetic impact that the project leads to technological solution.
Fig 11‐12. Perspective view of building unit in via Forno n. 17‐19
For the photovoltaic coverage installation a package was designed similar to that of raised access floor for outdoor use. The system can, in fact, to ensure such benefits, roof waterproofing, modules ventilation, easily inspected and maintainability of the fully integrated plant.
Fig 13. Photovoltaic paving stone construction detail
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On a wooden support structure consistent with the original system, consisting of beams (15 x 25 cm), joists (10 x 10 cm) in laminated wood and table (5 cm), there is a concrete slab, packed with expanded clay to a depth of 7 cm. Isolation is achieved by: bituminous prefabricated vapor barrier membrane reinforced with aluminum sheets, waterproof feltpaper 8 cm thick, sealing and waterproofing sheath both made of bitumen (Fig 13). On the latter plastic pedestals are arranged where the stone photovoltaic slabs will be placed. First the photovoltaic slab will be placed, then 66 stone slabs will be placed across the perimeter cuts to be made to measure.
CONCLUSIONS
The investigation and development of the prototype simulation for the case study showed how a specific design of components and systems for the exploitation of renewable energy sources to be integrated within significant historical and architectural areas is feasible and efficient. Specifically the application should be extended to the whole area according to a broader approach. It appears quite clear that these contexts, although more critical than new buildings, can not be excluded from the necessary evolution process that is changing the market in particular in terms of energy and performance demand. Nevertheless, in such contexts, the awareness of new technologies is highly recomended in order to further minimize the impact caused by plants on valuable buildings. This study is the initial phase of a wider research carried out by the Department of Architecture and Urban Planning at the Polytechnic of Bari. Specifically, the research aims to develop new technologies and prototypes using advanced technologies such as photovoltaic coatings composed by organic cells and photovoltaic optical fibers. The research on these topics and on the compatibility between new technologies and existing materials of the traditional heritage, supported by experimental investigation, is really challenging and interesting, In fact, it might address the application of strategies for the refurbishment and energy self‐sufficiency of historic buildings in the Mediterranean area.
References
(1) Energia per il futuro: le fonti energetiche rinnovabili – Libro Bianco per una strategia ed un piano d’azione per la Comunità, 1997. (2) Libro Verde – Verso una strategia europea di sicurezza dell’approvvigionamento energetico, Lussemburgo, 2001. (3) GreenBuilding, Improved Energy Efficiency for Non‐Residential Buildings, IEE Project. (4) EL‐TERTIARY, Monitoring Electricity Consumption in the Tertiary Sector, EU DG TREN IEE, 2006‐2007. (5) Passive‐On Project, EU Research DG, 2005‐2006. (6) KeepCool, Promotion of sustainable summer comfort in service buildings, EU Research DG, 2005‐2006. (7) IEA, “Energy efficiency requirements in building codes, energy efficiency polizie for new buildings”, Information paper in support of the G8 Plan of Action, 2008. (8) ECOFYS, “Mitigation of CO2 Emissions from the Building Stock”, DM 797. (9) SAVE Programme: Rehabilitation for Improving Energy Efficiency of the Buildings in the Historical Area 'Largo do Chafariz de Dentro' (Instituto de Tecnologia e Inovação oara a Modernização Empresarial (ITIME) Lisbon). (10) RENA Programme: Saline‐ Ostia Antica. Urban planning of a social area in the suburbs of Rome maximizing the use of renewable energies, respecting the environement and with the objective of reaching the "zero‐emission town (Azienda Comunale Energia e Ambiente di Roma). (11) SAVE Programme: Rehabilitation of old office buildings to improve their energy efficiency (A. N.Tombazis and Associates Architects LTD). (12) Energy Heritage, a guide to improving energy efficiency in traditional and historic homes, Changeworks Initiative. (13) Low Energy standars for existing Buildings, Project website: www.neh‐im‐bestand.de Besser als ein Neubau, Das Pilotprojekt, Niedrigenergiehaus im Bestand“.
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