“ESSE” project: a sustainable proposal

for the realization of social housing in Italy

Cristina Salvadori Architect ISAAC – energy systems engineering for built environment Italy salv.mat.k@katamail.com

Giacomo Salvadori Engineer, PhD ISAAC – energy systems engineering for built environment Italy giacomo.salvadori@

ordineingegneripisa.it

Summary The present work began as a challenge to one of the most complex aspects of the contemporary city: the creation of social housing available in short time, economic but also energy efficient and with strong architectural identity. The "ESSE" (in Italian Edilizia Sociale Sostenibile Efficiente) project is based on the use of a modular architecture that allows the creation of housing with elements of fixed size, favouring the pre-fabrication. In this work the “ESSE” project is applied to a case study of a residential complex which spread over 3 floors, with three residential units of different sizes: small sized unit, built with 3 modules (2 occupants, useful surface 46 m2), medium sized unit, 4 modules (3 occupants, useful surface 61 m2), large sized unit, 5 modules (4 occupants, useful surface 77 m2).

Keywords: Social housing, modular architecture, passive house, energy performance, light envelope structure

1. Introduction The focus on the sustainability of the built environment, especially in terms of energy performance of buildings that has became important from the legislative point of view after the adoption of EPBD/2002 [1], was recently confirmed in the EPBD recast/2010 [2]. In [2] it is required that by 31st December 2020 all the new buildings are nearly zero energy buildings, leaving the definition of nearly zero energy building to the individual member states of the EU. This paper describes an architectural proposal able to meet the requirements fixed in the Italian Legislative Decree 192/2005 [3] (Italian acknowledgment of the EPBD/2002), leaving the designers completely free in the characterization of the shape and appearance of buildings. The proposal is based on the concept of modular architecture, this choice is justified by the dynamicity of the system, able to adapt to different needs and to their changes. The contemporary house, according to the needs of society, has to be an increasingly changeable and adaptable space, no longer static. From monolithic and compact blocks of the Modern Movement [4], the residential architecture changes towards transparent forms, morphologically open, also the standardization changes levels and codes [5], [6], [7]. The modular architecture allows to obtain the aforesaid flexibility, with the benefits of a factory production, available in short time, economic and energy efficient, with strong architectural identity.

2. The description of ESSE project 2.1 Architectural features The ESSE project (in Italian Edilizia Sociale Sostenibile Efficiente) involves the construction of

Fig. 1 Examples of basic modules aggregation (L=length of basic module, W=width of basic module, garden areas painted in green, external paved areas painted in brown).

residential units for different numbers of people, with a maximum (for structural reasons) of three floors above ground and a basement.

The residential unit is obtained by the combination of a basic module and gives life to endless possibilities of aggregation. In this paper are shown just some examples of possible combinations, that are repeatable countless times and always with different results. The idea of the basic module, which is used to create living spaces, risen from the same philosophy with which the system Lego ® [8], the oldest line of toy building bricks, is built. These bricks are designed so that each element of any series is part of a system and is therefore compatible with all others, regardless of form, function and size. From these considerations, a basic module with proportion between the sides of 2/3, with dimensions of 3.2x4.8 m (WxL) and an useful surface of 15.4 m2, has been developed. The dimensions and the proportions of the basic module have been suitably selected after numerous tests, in order to find the optimal solution able to host at best all the living functions. By connecting different modules can be created a residential unit with different sizes and for different numbers of people. Different residential units can be assembled in turn giving rise to residential complexes; the aggregation possibilities that this system allows are endless. In this paper just some examples of aggregation are presented. The examples have been designed by considering residential units with number of occupants equal 2, 3 and 4. In particular: SMALL unit, consisting of 3 modules and designed for 2 occupants (useful surface about 45 m2); MEDIUM unit, consists of 4 modules, for 3 occupants (useful surface about 60 m2); LARGE unit, consisting of 5 modules, for 4 occupants (useful surface about 74 m2). These

three sizes have been subsequently assembled, pulled over and overlapped so as to compose different solutions, according to an enjoyable and exciting game of full and empty, as if these modules are plugs inserted or removed from their location to create ever new effects and without compromising the stability of the building. Figure 1 shows four examples (indicated by the letters A, B, C, D) of residential buildings over 3 floors, obtained through a combination of different basic modules, with three different sizes of residential unit (LARGE sized at ground floor, MEDIUM sized at frist floor, SMALL sized at second floor). 2.2 Example of application As a case study in this paper is analyzed a residential complex consisting of 3 floors, created using two times (with symmetrical duplication) the modules aggregation indicated with "A" in Fig. 1. The two blocks of the residential complex are connected by a stairwell outside, centrally located. In Fig. 2 the plan views with the distribution of the rooms are shown. On the ground floor are located the LARGE units, with the rooms listed in Table 1. The living area is an open space and it is located in the south-facing of the building, to receive all the daylight

coming from the openings that overlooking the terrace. The openings on the north side are minimal to reduce losses in winter.

Fig. 2 Plan views of the case study building: ground floor, first floor, second floor.

On the first floor are located the MEDIUM units (see Table 1). The basic module removed from the lower level has created a space to use as garden. Even in this case the openings on the south side are very large and shaded by solar mobile shades, on the north side instead there are only two openings for the bedrooms. On the second floor are located the SMALL units (see Table 1). The distribution of the rooms remains unchanged with respect to the lower floors. The location of the garden is shifted to the north, in order to exploit the coverage of the unit located below and leaving uncovered the garden of the apartment below. Of note that the terraces and the gardens are positioned in such a way as to be sheltered from view from the stairwell, to ensure privacy to users on all levels. The south elevation of the complex is one of the relevant elements of the project: the language of full and empty is made extreme here, not only with the use of green space located on multiple levels, which already provide a movement in the skyline, but also with the posibility to shift, and overlap the solar shades visible in the front view. In Figure 3 are shown 3D views of the south elevation (diurnal Fig. 3 left, nocturnal Fig. 3 right). The 3D views also differ for the choice of the solar shades, in one case obtained with orientable fins (Fig. 3a) in the other with polycarbonate screens with low light transmission index (Fig. 3b).

Fig. 3 3D views of the south elevation diurnal (left) and nocturnal (right).

Table 1 Useful surfaces of the rooms

3. Sustainability strategies In order to make the case study building more sustainable as possible, different strategies has been considered. Special attention has been paid to the design of the building envelope in order to minimize the energy consumption, this aspect is discussed in detail in the next paragraph; for the sake of overview, the other strategies, which have been considered for the sustainability of the building, are summarized below. The roof of the building is made entirely with a green roof, which is in some case used as a private garden, this not only improves the thermal and acoustic performance, the life cycle of the roof structure, but also helps to create a vegetal space that interacts with the environment by filtering dust and smog. Besides the different layers that make up a green roof, the heart of this system is the part draining, which not only guarantees the correct dosage of water to the soil, but allows to recover, through a special absorber system, the excess water that can be reused. Along the perimeter of the green roof some grids are installed for the collection of rainwater. The rainwater, together with the excess of water drained from the green roof, is firstly conveyed in tanks and purified and finally it is reused for the watering systems for the cycle of washing machines or for the discharge of the toilet. The rainwater recovery system can be sized to cover 50% of the annual requirement of water for the uses listed above. The terraces are equipped with appropriate solar mobile shades, that protect the glass surfaces from direct sunlight, avoiding high superheating of the rooms. The terraces in the winter can become solar greenhouses thanks to the presence of glass panels, contributing significatively to the heat gains. The glass panels can be opened in the summer, thereby avoiding superheating of the space. On the coverage of the stairwell and ground floor terrace is installed a photovoltaic system with panels made of polycrystalline silicon and amorphous silicon (for the most shaded areas), with a total surface of 42.4 m2 and a nominal electric power (at standard reference conditions) of 4 kW. The PV system is designed to cover more than 70% of the electric energy demand (except for heating and cooling) of the residential complex. On the coverage of the other terraces are installed solar collectors for a whole of 7.8 m2, which cover about the 50% of energy demand for domestic hot water (DHW) production. Finally the residential units are heated/cooled by radiant floor. The thermal power for heating/cooling is supplied by electric heat pumps with high thermal performance. The described strategies are schematically shown in Fig. 4. 3.1 Energy performance of building For the construction of the building a structural system with load-bearing walls made with wooden panels, prefabricated and portable, is used. The wooden panels arrive on site already designed to be mounted easily and quickly, ready to be integrated with the various building plants. The reasons

Room

Large unit

Medium unit

Small unit

Useful surface (m2)

Living and dinning room, kitchen 31.70 25.86 21.97

Bathroom 1 4.73 5.00 5.52

Bathroom 2 5.68 - -

Double bedroom 1 14.96 14.65 14.48

Double bedroom 2 14.96 - -

Single bedroom - 10.00 -

Hallway 1.94 4.25 2.70

Total indoor surface 74.12 59.76 44.67

Terrace 12.00 7.00 7.00

Green terrace - 15.00 17.15

Fig. 4 Sustainable strategies considered for the building during summer

of this choice are to be found both in reducing time and cost of construction and in the enormous potential offered by a material like wood: wood is natural, renewable and it has a good behaviour both in seismic zones and in the presence of fire.

The building system with wooden bearing panels involves the construction of solid wooden panels with cross layers, which are connected by mechanical elements and assembled to form box-shaped structures. The wooden panel chosen consists of a plywood (wood 99.5%, glue 5%) that can be considered a compact and sustainable product and can be used in buildings with bearing walls. Special attention has been paid to the choice of the stratigraphies of the opaque structures, in order to meet the requirements fixed by the Italian Legislative Decree 192/2005 [3] and to reduce energy consumption of building both during winter and summer. The stratigraphies of the main opaque structures (green roof and vertical external wall) are described respectively in Tab.s 2, 3, where D (m), ρ (kg/m3), r (m2·K/W), Cp (J/(kg K)) are respectively the thickness, the density, the specific thermal resistance and the specific heat of the single layer.

Tab. 2 Green roof stratigraphy

Tab. 3 External wall stratigraphy

With reference to the opaque structures, in Tab. 4 are shown the values obtained for the following parameters: thermal transmittance (U), dynamic thermal transmittance (UD), time lag (t) and decrement factor (f). As can be seen from Tab. 4 the values obtained for U and UD are well lower than the limit values more stringent (Ulim and UD,lim) fixed by Italian legislation. Furthermore, the values obtained for f and t allow the attribution of the label 1 "excellent performance" for the thermal summer behaviour of the building envelope, maximum label achievable according to the Italian Ministerial Decree 26th June 2009 on the energy labelling of buildings [9]. The thickness of the air duct, which is present in the stratigraphy of the vertical wall, is sized to achieve energy savings in summer conditions, according to the calculation models presented in [10], [11]. The air duct, closed during winter, can be hence opened in the summer, promoting the natural ventilation. For the case study, an evaluation of the primary energy demands, for space heating and DHW production, has been carried out, assuming for the building location the city of Florence (Italy). In particular, the energy performance indicators for space heating and DHW production, used in Italy [9] for the energy labelling of buildings have been calculated; they are defined as: EPi=Qh/(nh S) (1) EPdhw=Qhw/(nhw S) (2) with the following simbols: Qh (kWh/year) and Qhw (kWh/year) are the useful energy demand for space heating and for DHW production respectively, nh (n.d.) and nhw (n.d) the overall eficiency of the heating system and of the DHW production system rspectively, S is the useful surface (m2).

N. Material. D ρ r Cp

1 Substrate of soil and turf 0.20 1200 0.07 0.85

2 Filtering layer in polyethylene 1x10-4

1000 3x10-4

2.20

3 Drainage layer in polyethylene 0.05 950 0.14 2.20

4 Protection (felt+ polyethylene) 0.010 30 0.22 1.50

5 Waterproofing layer in bitumen 2x10-4

1080 0.01 0.92

6 Thermal insulation in XPS 0.06 30 1.67 1.25

7 Wooden floor 0.16 470 1.61 1.55

N. Material D ρ r Cp

1 Metal support for external facing - - - -

2 External layer in asbestos cement 0.02 560 0.07 0.98

3 Air duct 0.05 0.18

4 Thermal insulation in XPS 0.10 30 2.78 1.25

5 Wooden bearing wall 0.11 470 1.10 1.55

6 Thermal insulation in XPS 0.05 30 1.39 1.25

7 Internal layer in plasterboard 0.02 900 0.10 1.20

U

(W/m2K)

UD

(W/m2K)

t

(h)

f

(n.d)

Ulim

(W/m2K)

UD,lim

(W/m2K)

Green roof 0.26 0.007 21.6 0.028 0.29 0.20

External wall 0.17 0.005 19.6 0.035 0.33 0.12

Tab. 4 Thermal parameters of the building structure and limit values imposed by Italian legislation

For the analyzed building, using the methodologies specified in the technical standards of the series UNI/TS 11300 [12] and also considering the energy supplies derived from the exploitation of solar energy (especially from solar collectors), the energy performance indicators result: EPi=15.2 kWh/m2year, EPdhw=8.2 kWh/m2year. These values, according to [9] allow the attribution of the energy label A+ to the building (maximum label achievable). For economic comparison, the analysed building if realized with different solutions in order to obtain the energy label C (minimum label required by the Italian legislation for new buildings) would have an operating cost of about 1500 €/year higher than in the case in class A+ (considering an average cost of primary energy supply amounted to 0.1 €/KWh). 3.2 Sustainability rating with Guidelines for Sustainable Building in Tuscany The overall sustainability of the building has been assessed according to the Guidelines for Sustainable Building in Tuscany [13]. The method proposed in [13], according to the international method Green Building Challenge (GBC) is a score-system, based on the analysis of requirements weighed according to numerous qualitative and quantitative criteria, contemplating a range of scores included between -2 and +5. The score obtained for the analysed building is 4.14 points out of a maximum of 5. The high score has been obtained thanks to the use of recyclable materials in structures and strategies for effective exploitation of solar radiation, and also to the excellent thermal and hygrometric behaviour both in winter and in summer. The value of performance indicator k=EPI/EPI* shown in [13] has been also calculated (with EPI*=97.8 kWh/m2year maximum value allowed by Italian legislation for the analyzed building), which is equal to 0.15. In the new building regulations of different Italian towns (e.g. Pisa [14]) an energy evaluation criterion of buildings, according to the score obtained as to the indicator k, has been adopted. For values of k lower than 0.50 economical incentives are contemplated (e.g. a discount on the urbanization fees) as well as a proportional increase of the building gross area in order to promote the design of low-energy-consumption buildings. For values of k lower than 0.30 the maximum score equalling +5 for the overall performance for space heating is obtained.

4. Conclusion In the paper, a project of social housing with high sustainability features is proposed . The proposed project not only meets the main requirements of social housing, such as innovation, flexibility, integration, standardization and modularity, but it is also characterized as a solution with high energy efficiency, with the aim of reducing energy consumption and emissions of CO2, as highlighted in the recent EPBD recast. The good results obtained in terms of sustainability and efficiency did not adversely affect the architectural appearance, thus avoiding the compromise between quality and price too often predominant in the social housing design. 4.1 References [1] EUROPEAN PARLAMENT AND COUNCIL ON ENERGY EFFICIENCY OF BUILDINGS,

“Energy Performance of Building Directive 2002/91/EC”, EPBD 2002. [2] EUROPEAN PARLAMENT AND COUNCIL ON ENERGY EFFICIENCY OF BUILDINGS,

“Energy Performance of Building Directive recast 2010/31/EU”, EPBD recast 2010. [3] PRESIDENZA DELLA REPUBBLICA ITALIANA, Decreto Legislativo n. 192 del 19 Agosto

2005, “Attuazione della direttiva 2002/91/CE relativa al rendimento energetico nell’edilizia”(Modified and integrated by D.L. n. 311 del 29 Dicembre 2006 and by DPR n. 59 del 2 Aprile 2009) (in Italian).

[4] L. BENEVOLO, “L’architettura del nuovo millennio”, published by: Editori Laterza, Roma (Italy), 2006 (in Italian).

[5] A. IACOMONI, “Abitare lo spazio flessibile”, Macramè, Vol. 2, 2008, pp. 53-61 (in Italian). [6] M. CUCINELLA “A home for 100.000 €”, www.casa100k.com [7] A. ARIEFF, “The Dwell house”, Dwell, Vol. july/august 2003, pp. 74-92 [8] LEGO toy building brick, www.lego.com [9] MINISTERO ITALIANO DELLO SVILUPPO ECONOMICO, Decreto ministeriale del 26

Giugno 2009, “Linee giuda nazionali per la certificazione energetica degli edifici” (in Italian).

[10] M. CIAMPI, F. LECCESE, G. TUONI, “Ventilated facades Energy performance in summer cooling of building”, Solar Energy, Elsevier, 2003, Vol. 75, Issue 6, pp. 491-502.

[11] G. TUONI, M. CIAMPI, F. LECCESE, G. SALVADORI, ”Passive cooling of buildings: ventilated facades and roofs”, proceding of CLIMA 2010, 10th REHVA world congress, Antalya (Turkey) 2010, ISBN 978-975-6907-14-6, Vol. CD-ROM, paper n. R1-TS33-PP02, pp. 1-8.

[12] UNI/TS 11300, “Prestazioni energetiche degli edifici – Climatizzazione e preparazione acqua calda per usi igienico sanitari”, 2008 (in Italian).

[13] REGIONE TOSCANA, “Linee guida per l’edilizia sostenibile in Toscana”, Delibera della giunta regionale n. 218 del 3 Aprile 2006, www.rete.toscana.it (in Italian).

[14] COMUNE DI PISA ( Assessorati Ambiente, Urbanistica ed Edilizia privata),”Regolamento edilizio – Norme per l’edilizia sostenibile”, 2009 (in Italian).