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Designing Sustainable Urban Futures

 | 
Marius Albiez
, 
Gerhard Banse
, 
Kenyon C. Lindeman
, 
et al.

3. Opportunities and Challenges for Sustainable Cities

eco-com.60+: Communal Living for the Elderly

Ecological, Social and Economical Aspects

Freya Brandl

Testo integrale

1 Introduction

1Demographic change in Europe reflects an aging population. In Austria, an increasing number of the elderly in larger cities live alone in large dwellings (cf. Häberlein 2006). This results in unnecessarily high demand levels of not only energy, but also spatial and financial resources. Despite these circumstances, there is currently a lack of alternatives to living in conventional dwellings. There are indications that an increasing number of the elderly would prefer “living together apart”, which means occupants spend a certain period of the day in their own spaces but part of the day is dedicated to communal living (cf. Durett 2009). In this context, the present paper explores the related topics of sustainability and energy efficiency for this population.

2The hypothesized advantages of communal living models lie in the higher occupancy density as well as shared use of certain spatial resources. This paper explores this potential via numeric simulation. A communal living model is virtually integrated in existing houses in a specific district of Vienna and compared with conventional solutions. Moreover, this “densification” effect is both compared and combined with the energy efficiency effects of thermal retrofits of the respective buildings.

2 Method

2.1 Heating Load of Selected Objects

3The 6th district of Vienna was selected for this research: it is situated close to the center of the city and has an urban texture with an existing infrastructure (e.g. coffeehouses and restaurants, public transportation, shops, and cultural amenities). Furthermore, it has an aging population and a large building stock in need of retrofitting.

4Two buildings of different construction periods were selected. Building “A” is a socalled “Gründerzeit-Haus”, constructed around 1900/1910. The building has four stories and is about 20 m high. The external walls are made of common brick with a thickness of about 50 cm. The façade overlooking the street includes decorative features and is thus not suitable for thermal retrofit via external insulation. The apartments in this building type are relatively generous in size: the third floor, which is selected for the present study, contains three apartments with 80 m2 to 130 m2 net floor area (see Figure 1).

Figure 1: External View of Building A

Figure 1: External View of Building A

Author’s Archive

5Building “B” is representative of buildings erected around 1950/1960. The building has six stories and two attic apartments, and is about 24 m high. The three upper stories were selected for the study, containing eight apartments with net floor areas (for each) ranging between 40 m2 and 80 m2 (see Figure 2).

6Two occupancy models were considered: the first (individual) model which represents the current circumstances in many instances, assumes that a single occupant lives in each apartment. The second (communal) model assumes a higher occupancy via smaller individual apartments but involving shared (jointly used) areas. For each of these models, two sets of construction-related assumptions were considered: the first (existing) assumption denotes as-is construction features. The second assumption denotes thermally retrofitted constructions (see Table 1). For these four scenarios, (heating) energy demand was computed using a dynamic thermal simulation application (cf. EDSL 2011). Thus, the energy efficiency benefits of the communal living models could be compared with benefits associated with thermal retrofit measures. Table 2 gives a summary of the respective scenarios and the associated code. Note that in this table and the paper, the following abbreviations were used:

A: building A,
B: building B,
I: existing occupancy model (individual),

C: communal occupancy model,
E: existing thermal state of the buildings,
R: retrofitted thermal state of the buildings.

7For example, B3_I_R denotes the third scenario for building B, individual occupancy model, thermally retrofitted.

Figure 2: External View of Building B

Figure 2: External View of Building B

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Table 1: Overview of the Assumptions

Table 1: Overview of the Assumptions

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Table 2: Simulation Scenarios for the Two Buildings with Respective Abbreviations

a

b

A1_I_E

B1_I_E

A2_C_E

B2_C_E

A3_I_R

B3_I_R

A4_C_R

B4_C_R

Author’s Archive

8Figures 3 and 4 illustrate the existing (individual) and the proposed (communal) occupancy models for building A respectively. Thereby, the existing three apartments are converted into five apartments: four single occupancy (net floor area around 50 m2) and one double occupancy (72 m2). Each apartment is equipped with a bathroom and a kitchenette. While the apartment sizes are smaller in the communal model, a relatively large space is provided for communal living including a living space with kitchenette and dining area, as well as a library or office room. Also some of the appliances are shared (washing machine, etc.).

Figure 3: Existing Floor Plan – Building A (individual)

Figure 3: Existing Floor Plan – Building A (individual)

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Figure 4: Selected Floor in Building A – New Layout (communal)

Figure 4: Selected Floor in Building A – New Layout (communal)

Author’s Archive

9Likewise, in the three selected floors of building B, instead of the existing eight apartments, ten smaller apartments (seven single and three double occupancy) are housed. Moreover, a shared living room including a kitchenette and a dining area, a library or office room, a guest room and a rooftop terrace have been implemented. Figures 5 to 8 show the corresponding individual and communal occupancy models. Assumptions pertaining to the two buildings and the two occupancy models are summarized in Table 3.

Figure 5: Existing Floor Plan – Building B, attic (individual)

Figure 5: Existing Floor Plan – Building B, attic (individual)

Author’s Archive

Figure 6: Existing Floor Plan – Building B, 5th and 6th Floor (individual)

Figure 6: Existing Floor Plan – Building B, 5th and 6th Floor (individual)

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Figure 7: New Layout – Building B, attic (communal)

Figure 7: New Layout – Building B, attic (communal)

Author’s Archive

Figure 8: New Layout – Building B, 5th and 6th Floor (communal)

Figure 8: New Layout – Building B, 5th and 6th Floor (communal)

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10The differences in the assumed occupancy conditions and processes between the individual and communal occupancy models result in corresponding simulation input assumptions regarding internal gains. These assumptions are summarized in Table 4.

Table 3: Summary Information on Simulated Objects

Table 3: Summary Information on Simulated Objects

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Table 4: Assumed Internal Loads [W.m–2]

Table 4: Assumed Internal Loads [W.m–2]

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11As mentioned before, buildings A and B are considered both in their present condition as well as after an assumed thermal retrofit. Thereby, exchange of windows and, where possible, improved thermal insulation of the external walls were taken into account. Table 5 provides an overview over the U-Value assumptions for the respective simulation models.

12As the pertinent performance indicator, annual heating loads were calculated for both buildings. A standard weather file for Vienna was used (cf. Meteotest 2008). The computed heating loads were expressed either per net floor area of the dwellings or per occupant.

Table 5: U-Value Assumptions for Walls and Windows [W.m-².K-1]

Table 5: U-Value Assumptions for Walls and Windows [W.m-².K-1]

Author’s Archive

2.2 Estimation of City-wide Energy Saving Potential

13Subsequent to the simulation of the heating loads for the selected objects, an effort was made to roughly estimate the wider energy saving potential for the city of Vienna. The pertinent assumptions for this extrapolation exercise were as follows

  • Based on available data on the current age distribution of Vienna’s population (cf. MA 2011), it can be estimated that, by the year 2035, approximately 600,000 people in the city of Vienna will be between 60 and 85 years old.

  • It is conceivable that with appropriate information campaignes and policy measures, 10% of the above population (i.e., roughly 60,000 people) could be housed in communal living settings as opposed to individual dwellings. The occupancy density for these two options may be assumed to be 50 and 100 m2 per person respectively, given an appropriate weighting of the information provided in Table 3.

3 Results

3.1 Heating Loads of the Selected Buildings

14Tables 6 and 7 summarize the simulated heating loads (per m2 net floor area and per occupant) for the two reference buildings (A, B) and the four scenarios (see Table 2). This information is shown in Figures 9 and 10 in relative terms, i.e. percentage reduction for scenarios 2 to 4 as compared to scenario 1.

Table 6: Heating Load for Building A

kWh.m2.a1

kWh.person1.a1

A1_I_E

76.70

8,795

A2_C_E

61.54

3,802

A3_I_R

49.23

5,645

A4_C_R

34.77

2,150

Author’s Archive

Table 7: Heating Load for Building B

kWh.m2.a1

kWh.person1.a1

B1_I_E

87.38

5471

B2_C_E

76.56

2983

B3_I_R

19.82

1241

B4_C_R

16.78

654

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Figure 9: Reduction of the Heating Load per m2 per Year Compared to the Existing Buildings [%]

Figure 9: Reduction of the Heating Load per m2 per Year Compared to the Existing Buildings [%]

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Figure 10: Reduction of the Heating Load per Person and Year Compared to the Existing Buildings (%)

Figure 10: Reduction of the Heating Load per Person and Year Compared to the Existing Buildings (%)

Author’s Archive

3.2 Estimated City-level Heating Load Reduction

15The estimated annual heating load reduction extrapolated to the entire city of Vienna would amount to 366 GWh, if by the year 2035 10% of the population in the age bracket 60 to 85 would be living in communal settings, instead of in single apartments. This corresponds to an estimated 77% reduction in heating energy use.

4 Discussion

4.1 Heating Load

16The two instances of buildings selected for the present study (objects A and B) are not necessarily representative for all buildings in Vienna in strict statistical terms. Nonetheless, the situations they display (size, construction type, number of floors, etc.) are quite common. Thus, certain general inferences could be derived from their treatment in the above analysis, even though the introduction of communal living inadvertently results in changes in the total net floor areas of the apartments and the number of occupants (see Table 3).

17The simulation results suggest that the thermal retrofit of the selected objects A and B (without introducing the communal living layout) would reduce the area-specific heating load by 36% and 77% respectively. The better result in the case of building B is due, in part, to the rather poor thermal characteristics of this building in its current state, as documented in Table 5. Moreover, the thermal insulation of the street-facing (decoratively articulated) external walls of building A could be only minimally improved.

18Introduction of the communal living pattern without thermal retrofit would result in 20% and 12% heating load reductions in buildings A and B respectively. Both measures combined (thermal retrofit and communal living) would result in 55% and 81% heating load reductions. The energy efficiency effect of the communal living could be even more impressively illustrated if we consider heating load reductions per occupant. In that case, communal living (without thermal retrofit) would result in 57% and 45% heating load reductions for buildings A and B respectively. This implies that the per occupant energy efficiency improvement potential of the communal living scenario is comparable in magnitude with full thermal retrofitting of buildings. Obviously, the combination of both measures’ results would represent the optimal solution. Thereby, heating loads could be reduced 55% and 81% (area-specific) or 76% and 88% (per occupant).

4.2 Additional Considerations

19Our rough extrapolation of the above results on the urban scale for the city of Vienna points to a significant heating energy reduction potential. The estimated heating load reduction, if adjusted with a bulk factor of 0.3 for the efficiency of the heating systems, results in a delivered heating energy reduction of 520 GWh. Needless to say, aside from energy conservation, the communal living pattern would also bring about large savings in space usage (approximately 3 million square meters in terms of net floor area). This freed space could then be used for other occupants (families, young people, etc.) increasing thus not only space-use efficiency but also contributing to a more heterogenic (multi-generational) age structure. Our experience shows that, given proper architectural design, the reduction of area per occupant must not result in a loss of privacy or living quality. In fact, communal living has been shown to improve the life quality for many people.

20Moreover, increased occupancy in the city proper would reduce urban sprawl and the associated rise in traffic and virgin land usage. Likewise, the existing infrastructure (e. g. shops, services, transportation) would be used more efficiently and the competitiveness of the inner district as a business location could be improved.

21Aside from the calculated effects of such communal living models, there are additional benefits that appear feasible but are difficult to quantify:

  • Communal living models bring people with different capabilities or disabilities together. In such groups, the potential for mutual support could reduce the need for interventions from outside and the associated energy and financial resources (e.g., for delivery and service trips).

  • Increasing the occupancy density in the inner districts of the city makes it more convenient to participate in cultural and recreational activities. Places can be reached with public transport and if transportation services are needed, the distances are shorter (and the service can be used by more than one occupant at a time).

  • Socially, the effects of such communal living models are manifold. Experiences with similar projects in different countries show that the groups grow together, regular group activities are organized, and the occupants feel less lonely and also much more secure, as they are surrounded by familiar people.

Bibliografia

References

Durett, C. (2009): The Senior Cohousing Handbook – A Community Approach to Independent Living. Gabriola Island, Canada

EDSL (2011): A-TAS Version 9.2.1. Environmental Design Solutions Limited. – URL: www.edsl.net

Häberlein, U. W. (2006): Lebens-& Wohnformen – Singles in Wien. Entwicklung zur Privatheit und Funktionalisierung der Räume. In: Beiträge zur Stadtentwicklung, Nr. 04 (MA 18, Stadtentwicklung und Stadtplanung). – URL: https://www.wien.gv.at/stadtentwicklung/studien/pdf/b008042.pdf [May 2011] (in German)

Magistrat der Stadt Wien (2011): Bevölkerung nach Altersgruppen und Staatsangehörigkeit 2006 bis 2008. Wien (MA 05, Stadt Wien. Vienna, Austria). – URL: www.wien.gv.at/statistik/bevoelkerung/demographie/bevoelkerungszusammensetzung.html [May 2011] (in German)

Meteotest (2008): Meteonorm Version 6.1. – URL: www.meteonorm.com

Indice delle illustrazioni

Titolo Figure 1: External View of Building A
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-1.jpg
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Titolo Figure 2: External View of Building B
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-2.jpg
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Titolo Table 1: Overview of the Assumptions
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-3.jpg
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Titolo Figure 3: Existing Floor Plan – Building A (individual)
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-4.jpg
File image/jpeg, 68k
Titolo Figure 4: Selected Floor in Building A – New Layout (communal)
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-5.jpg
File image/jpeg, 76k
Titolo Figure 5: Existing Floor Plan – Building B, attic (individual)
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-6.jpg
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Titolo Figure 6: Existing Floor Plan – Building B, 5th and 6th Floor (individual)
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-7.jpg
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Titolo Figure 7: New Layout – Building B, attic (communal)
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-8.jpg
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Titolo Figure 8: New Layout – Building B, 5th and 6th Floor (communal)
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-9.jpg
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Titolo Table 3: Summary Information on Simulated Objects
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-10.jpg
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Titolo Table 4: Assumed Internal Loads [W.m–2]
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-11.jpg
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Titolo Table 5: U-Value Assumptions for Walls and Windows [W.m-².K-1]
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-12.jpg
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Titolo Figure 9: Reduction of the Heating Load per m2 per Year Compared to the Existing Buildings [%]
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-13.jpg
File image/jpeg, 44k
Titolo Figure 10: Reduction of the Heating Load per Person and Year Compared to the Existing Buildings (%)
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URL http://books.openedition.org/ksp/docannexe/image/4231/img-14.jpg
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Autore

A research project in cooperation with Ardeshir Mahdavi and Kristina Kiesel, Vienna University of Technology.
Arch. Dipl.-Ing. Dr. techn, Institute of Architectural Sciences, Vienna, Austria; freya.brandl@tuwien.ac.at.

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