Energy Refurbishment Towards Nearly Zero Energy Multi-family Houses, for Cyprus

Available online at www.sciencedirect.com

ScienceDirect Procedia Environmental Sciences 38 (2017) 11 – 19

International Conference on Sustainable Synergies from Buildings to the Urban Scale, SBE16

Energy Refurbishment Towards Nearly Zero Energy Multi-Family Houses, for Cyprus D.K.Serghidesa,*, M.Michaelidoub, M.Christofic, S.Dimitrioud and M.Katafygiotoue a,d b,c,e

The Cyprus Institute/Energy,Environmenta and Water research Center, 20 Konstantinou Kavafi Str., 2121, Aglantzia, Nicosia, Cyprus Cyprus University of Technology/Department of Civil Engineering and Geomatics, 30 Archbishop Kyprianou Str., 3036, Limassol Cyprus

Abstract Following Europe’s 20:20:20 objective, this case study investigates refurbishment scenarios in order to achieve Nearly Zero Energy houses, in Cyprus. The study investigates amongst other aspects of the European recast, two approaches that will be decisive for the development of the building sector in Cyprus: The measures and techniques to be implemented in order to achieve nearly Zero Energy Houses (nZEB) in Cyprus and the analysis of cost optimisation. The research focuses on the MultiFamily House typology as classified in the framework of EU project EPISCOPE. The building was modelled using the official governmental software iSBEM_cy tool, according to the European Directives 2002/91/EC and 2010/31/EC. The aim was to upgrade it into a nearly Zero Energy Building (nZEB) by investigating the effectiveness of the energy refurbishment both in terms of energy savings and payback period. Two scenarios were developed in order to evaluate the energy efficiency and the cost effectiveness of the conservation measures. Through analysis of the results, the efficiency of each strategy and technique employed towards minimising the energy consumption and the greenhouse gas emissions was evaluated, in terms also of its cost effectiveness. Furthermore, the results of the research were investigated in order to assess whether the nZEB requirements, as developed by the MECIT, are appropriate for the existing Multi-Family houses in Cyprus and whether alternative strategies may be employed in order to meet the target of nZEB and to reduce effectively the energy consumption and the CO2 emissions. © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2017 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-reviewunder under responsibility of organizing the organizing committee of SBE16. Peer-review responsibility of the committee of SBE16. Keywords: Multi-Family Housing; Nearly Zero Energy Buildings; Cost-effectiveness

* Corresponding author. E-mail address: [email protected].

1878-0296 © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of SBE16. doi:10.1016/j.proenv.2017.03.068

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1. Introduction The residential stock is the biggest segment of EU floor space, reaching 75% of the total building stock, which accounts for 63% of the total energy consumption. In EU-25 there are about 196 million dwellings, with more than 50% of the existing residential buildings built before 1970 and about 1/3 of the dwellings built during 1970-19901. Raising the bar for new buildings — especially given the explosion of new green building technologies and the growing popularity and accessibility of sustainable design — stimulates innovation and creates future environmental benefits. However, existing buildings in built-out cities are going to be responsible for the vast majority of resource use over any meaningful planning period. While new constructions add at most 1% a year to the existing stock, the other 99% of buildings are already built and produce about 26% of the energy-use induced carbon emissions2. Thus, one of the greatest challenges in urban sustainability today is energy retrofitting or greening the existing buildings. Taking into account that the expectation for the structural life of a building often exceeds 60 years, while the envelope shows signs of obsolescence after only in 20 or 30 years2, it is understandable that a building completed in 2010 will undergo refurbishment during the next 10 to 20 years. Within the residential sector, different types of single family houses (e.g. detached, semi-detached and terraced houses) and apartment blocks are found. Across the EU-25 countries, 64% of the residential building floor area is associated with single family houses and the remaining 36% with appartments3. There is no “one size fits all” approach to retrofitting the multifamily housing stock. Multifamily buildings vary widely in terms of heating, ventilation, and air-conditioning (HVAC) and other relevant systems, building age, building size, tenant incomes, financing structures, ownership structures and other important factors that may affect energy efficiency and related decision-making. Policies must accommodate and reflect the diversity of both the building stock and its stakeholders. Multifamily buildings account 21.7% of the total building stock in Cyprus. Although they tend to be energy efficient, on a per capita basis, because their shared-wall geometry means that less heating and cooling are lost to the exterior4, they have been identified as a particularly challenging area for energy conservation 1. Many owners prefer to perform improvements at unit turnover. However, by renovating on a unit-by-unit basis, owners lose the economic benefits from retrofitting the entire building at once. Very little data on the actual energy performance of multifamily properties is currently available, making the benefits of energy efficiency improvements difficult to quantify. Determining the most effective measures for multifamily housing energy performance will maximize both the ability of policies to advance energy efficiency within the sector and the compliance of the owners/stakeholders 5. According to the law N.210 (I)/2012 it is necessary for each building or dwelling under construction or big scale renovation to proceed to energy audits and to issue Energy Performance Certificates (EPC). This is obligatory for buildings or dwellings to be sold or to be rent, resulting the increase both of the property’s value and cost attractiveness.

2. Methodology According to the IEE Project TABULA and the ongoing IEE Project EPISCOPE 6, twelve residential building typologies were established as typical and representative of the national residential building stock in Cyprus7. These are classified according to their chronological period of construction and their architectural and constructional characteristics. The three building typologies consist of the Multi Family Houses (MFH), the Terrace Family Houses (TH) and the Single Family Houses (SFH). These are further divided into four different chronological periods, supported by the data collected from the Cyprus Statistical Service 8. Each chronological division was defined based on the different constructional regulations and techniques that were applicable throughout the years, formulating the four distinctive chronological categories. These categories are the following: 1) before 1980, 2) between 1981 and 2006, 3) between 2007 and 2013 and 4) after 2014. The divisions were also guided by the rapid growth of the construction industry in Cyprus, which occurred after 1980, by the adoption of the European Directive 2002/91/EC in 2007 and the amendment of the Directive 433/2013, which was enforced in the beginning of 2014. Before the entrance of Cyprus in the European Union, there was no energy related legislation for the building sector.

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The building under study was selected according to its space-related characteristics, which approach those of the typical Multi-Family House of the first chronological period. When this study was conducted, due to the lack of available data, mainly concerning the installed electromechanical systems, certain assumptions were made (length and type of pipes, condition of systems and energy efficiency)9. Initially, the energy performance of the existing state was calculated based on the energy performance of each apartment individually. The apartments were grouped by floor and the total energy consumption for all three floors was calculated. Subsequently a standard nZEB refurbishment scenario was applied, based on the Directive 366/2014. The energy efficiency and the cost viability for each refurbishment measure related to the building's envelope elements’ thermal performance was assessed separately for three (3) apartments on different floors. Additional measures were examined in terms of their energy efficiency and cost effectiveness. Based on the findings, an optimized nZEB scenario was developed, oriented to improve the energy efficiency and cost effectiveness of the refurbishment. The investment cost associated with the nZEB refurbishment scenarios, as well as the payback period, were based on the current market values. These were calculated with the official tool provided by the Ministry of Energy, Commerce, Industry and Tourism of Cyprus for the cost optimal energy conservation measures10. The modeling tool used in this study for the energy performance calculation is the iSBEM-Cy, the governmental software for the issuance of Energy Performance Certificates11, used for the categorization of energy efficiency in buildings and the calculation of CO2 emissions according to the European Directive 2002/91/EC12. 3. Case Study 3.1. The building general information The case study concerns an 8-storied Multi-Family House (MFH) of 24 apartments with pilotis, a free open space in the ground floor, used mainly as parking space. It is situated in Ayios Tychonas in the coastal city of Limassol. The block of flats was constructed in 1973 and is representative of its typology for the chronological period before 1980. This MFH was built before the launching of the Directive 568/2007 13, with no thermal insulation. Nonetheless, stricter Directives14 are now in force and big renovation of the apartments is expected to take place in the next 20 years. Therefore, identifying the most energy and cost efficient refurbishment measures towards this direction is necessary. A typical floor plan of the building is shown in Figure 1.

N

Fig. 1. Floor and apartments’ layout and orientation.

The common spaces (staircases, elevators and corridors) are developed in such a way as to separate the apartments in Northeast, Northwest oriented and Southern oriented. The usable heated living area and volume per floor is presented in Table 1.

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Table 1. Existing Condition - Building components area and volume. Volume

Wall Area Total

Fenestration

Wall Area

Exposed Floor

Exterior Roof

m³

m²

m²

m²

m²

m²

First Floor

1408.65

469.55

82.75

386.80

294

--

Mid Floor

1408.65

469.55

82.75

386.80

--

--

Last Floor

1408.65

469.55

82.75

386.80

--

294

Floor

3.2. The existing condition of the dwellings For the simulations, each apartment is considered independently. The common wall between apartments is considered as adjacent to a heated space. The load-bearing structure of the building is made of reinforced concrete while the walls are of conventional brickwork, with plaster coating on both sides, resulting to a total thickness of 25cm. The windows are single-glazed with aluminum frame. The glazing area corresponds to a 18% of the total envelope area of each floor. The horizontal roof is made of a 15 cm reinforced concrete. The concrete floor slabs are cladded with 3 cm thick marble tiles. The U-values of the building envelope are shown on Table 2. Table 2. Existing condition - Buildings elements U-values. Technical specifications - Construction Element

U-Value W/(m2K)

External walls

1.389

Roof

4.107

Floor

2.072

Single glazed windows

6.000

Columns

2.539

Pilotis

2.836

Beams

3.258

For this study's purposes, it was considered that all the apartments are using split-units for cooling, installed in all rooms, including the bathroom and the corridor, and oil boiler for central heating. The SEER value of the units is 2, corresponding to default system. All nine (9) apartments use solar thermal panels for Domestic Hot Water, backed up by an electric element. After simulating each of the dwellings, the mean calculated Total Primary Energy Consumption is 708 kWh/(m²a) for the first floor, 501 kWh/(m²a) for a typical middle floor and 944 kWh/(m²a) for the last floor. The Primary Energy Consumption is higher for the dwelling of the floors that have large exposed surface areas , compared with the apartment of the typical middle floor. The 7 kWh/(m²a) of the Total Primary Energy Consumption for each dwelling are produced from Renewable Energy Sources (RES), attributed to the solar thermal panels on the roof for DHW consumption for all the dwellings. Therefore, the renewable energy contribution in the total primary energy consumption ranges from 0,7 % to 1,8 %. Table 3. Energy Consumption and CO2 emissions – Existing state.

Floor

First

Final Energy Heating

Final Energy Cooling

Primary Energy Consumption

Final Energy Consumption

Mean Primary Consumption per Floor

CO2 emissions

kWh/m2

kWh/m2

kWh/m2

kWh/m2

kWh/m2

kgCO2/m2

A

29.25

228.84

711.36

280.8

B

37.25

186.73

605.86

246.46

C

25.08

266.95

808.07

314.15

Ap. Unit

708.43

Class

Primary Energy RES kWh/m2

207.51

F

7

176.03

E

7

236.19

F

7

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Mid

Last

A

14.65

160.37

510.45

197.73

B

21.35

113.76

391.33

157.59

C

10.19

196.22

600.74

228.53

A

41.18

310.82

945.84

374.71

B

50.86

268.85

841.89

342.19

C

37.14

349.86

1045.21

409.12

Average

29.66

231.38

717.86

283.47

209.4

500.84

944.31

149.27

E

7

113.85

D

7

176.08

Ε

7

275.78

G

7

244.69

G

7

305.23

G

7 7

The corresponding energy consumption for heating ranges from 10.19 kWh/(m 2a) to 50.86 kWh/(m2a), with the highest consumption observed in Northeast oriented apartment (B) of the last floor and the lowest consumption in Northwest oriented apartment (C) of the middle floor. The corresponding energy consumption for cooling ranges from 113.76 kWh/(m2a) to 349.86 kWh/(m2a), with the highest consumption observed in Northwest oriented apartment (C) of the last floor and the lowest consumption in Northeast oriented apartment (B) of the middle floor. The Energy Performance Certificate (EPC) results to better categorization for the apartments of middle floor following by the ones of the First floor and Last floor as shown in Table 3. 3.3. The Standard nZEB Refurbishment Scenario According to the Cyprus EPBD Directive 366/2014 14 and in order to define a Zero Energy building, specific U-values of the elements of the building envelope must be obtained and certain minimum energy performance requirements must be fulfilled. These requirements are shown in Table 4. Table 4. nZEB Energy Requirements. NZEB REQUIREMENTS FOR HOUSES Technical specifications - Construction Element

U-value W/(m2K)

Pitched roof with horizontal ceiling

0.40

External walls

0.40

Double glazed windows

2.25

Energy Performance specifications

Minimum requirements

Energy Performance Certificate

A

Total Primary Energy consumption

100 kWh/(m2a)

Energy Demand for heating

15 kWh/(m2a)

Renewable energy percentage of the total primary energy consumption

25%

In order to meet the minimum set requirements for the building envelope for the nZEB Directive, 60 mm of thermal insulation (extruded polystyrene) were added externally to the walls and 70mm to pilotis, roof, columns and beams, obtaining U-values 0.38 W/(m2K) for these elements. The single windows were replaced with double windows, thermally improved ones, of lower U-value, 2.20 W/(m2K). Furthermore, 3 photovoltaic panels (4.8m²) were placed on the roof for each Southern oriented apartment under study and 2 photovoltaic panels (3.2m²) were placed on the roof for each Northeast and Northwest oriented apartment under study, with a south inclination of 30˚. The existing AC units were substituted with A+++ class units. The apartments with southeast and southwest oriented windows needed the addition of horizontal overhangs in order to meet the requirements.

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3.3.1. The standard nZEB scenario energy performance Using the above measures the energy performance of all the apartments was upgraded to A Category and met the requirements of the nZEB definition for residential buildings under deep renovation 15, except the total primary energy consumption that was set 100 kWh/m2a. Only one apartment (Ap. B of Mid Floor) met all the requirements and can be categorized as nZEB. The reductions in the total primary energy consumption per floor compared with their existing state are 84%, 79% and 88%, for the first, the middle and the last floor respectively. The contribution of Renewable Energy Sources (RES) ranged between 26 to 33 kWh/(m 2a) for all the apartments, covering from 25.5% to 32.6% of the total primary energy consumption. Table 5. Energy Consumption and CO2 emissions – standard nZEB scenario.

Floor

First

Mid

Last

Final Energy Heating

Final Energy Cooling

Primary Energy Consumption from Conventional Sources

kWh/m2

kWh/m2

kWh/m2

kWh/m2

A

1.11

16.77

78

38.44

B

1.81

12.88

76

35.29

C

0.89

20.93

91

42.34

A

0.38

16.36

75

37.3

B

0.56

11.42

64

32.58

C

0.13

20.64

88

41.29

A

0.95

17.29

79

38.8

B

1.58

13.3

72

35.48

C

0.74

21.5

92

Average

0.90

16.78

79.44

Ap. Unit

Final Energy Consumption

Mean Primary Consumption per Floor

CO2 emissions

kWh/m2

kgCO2/m2

Class

Primary Energy RES

kWh/m2

22.89

A

33

22.43

A

26

26.63

A

31

21.98

A

33

18.88

A

31

25.8

A

31

23.17

A

33

21.19

A

31

42.76

26.96

A

31

38.25

23.32

111.33

107

112.33

31

3.3.2. The payback period For the calculation of the payback time was based on current market values that obtained from the suppliers. The energy expenditure (Euros) was also calculated based on the prices provided by the Cyprus Electricity Authority. In addition, an annual inflation of 3% on the electricity price was considered. The payback period was estimated per floor, since an agreement between all owners of the first and last floor is necessary in order to refurbish pilotis and roof, respectively. The payback time for the first floor is calculated to be 4.5 years, 6.5 for the middle and 4.5 for the last. Therefore, the payback time makes the employed refurbishment measures an attractive plan to the owners, aiming at a maximum payback period of 10 to 15 years. The refurbishment measures applied in this scenario were investigated for three (3) apartments with the same orientation on different floors, in order to conclude to their energy efficiency and their cost effectiveness.

D.K. Serghides et al. / Procedia Environmental Sciences 38 (2017) 11 – 19

3.4. Impact of the Energy Conservation Measures and their Cost-Effectiveness The impact of each measure addressing the buildings’ envelope energy performance upgrade was separately investigated for 3 apartments of the same orientation (Southern) in order to detect the most cost optimal ones. The measures investigated were: 1) placement of insulation on the roof, the pilotis and the external walls, 2) replacement of windows, 3) installation of horizontal overhangs above the south facing windows, 4) installation of split-units both for heating and cooling and 5) placement of photovoltaic systems. The highest energy savings for all 3 apartments are obtained through the replacement of central oil heating with split units both for heating and cooling, A+++ class (with energy savings exceeding 41000kWh/year), followed by the roof and pilotis insulation addition for the third and first floor respectively, the placement of shading devices, the windows replacement and the wall insulation. Overall, the least energy efficient measure is the installment of the PV panels, since the percentage of RES contribution was set by the definition of nZEB to 25% of the total energy consumption (Fig. 2.).

Fig. 2. Energy Savings per refurbishment measure.

Cost analysis showed that the most cost-effective measure is the placement of horizontal overhangs in the Southeast and Southwest orientations, with 0.5 year for amortization of the initial investment. The second measure is the replacement of the central oil heating system with spit units of A+++ efficiency with a payback period of 1 year (Fig. 3). The remaining refurbishment measures result to payback periods less than 5 years and are therefore considered to be economical investments.

Fig. 3. Cost effectiveness per refurbishment measure.

3.5. Optimised nZEB refurbishment Scenario From the evaluation of the energy and cost effectiveness results, it was considered necessary to develop an alternative nZEB Scenario for the Multi-Family House that aims in maximizing the effectiveness of the

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refurbishment, both in terms of energy savings and payback period. The Scenario includes the placement of horizontal overhangs on the south-facing windows and the installment of PV panels for each floor, increased from the initial standard nZEB Scenario from 7 to 20 units, amounting to 32m2. The maximum permissible potential of PV’s installment is 5kW per dwelling15 but the total area of the building’s roof allowed one system for each floor only. The walls, roof and pilotis will not be further insulated and the existing single glazed windows will be changed with double glazed, retaining the U-values as presented in Table 2. 3.5.1. The optimised nZEB scenario energy performance Using the above energy conservation measures, all apartments were raised to A EPC category. The calculated total primary energy consumption for the optimized nZEB refurbishment scenario is reduced to 100 kWh/(m 2a) and less for all the apartments with percentage reductions in the total primary energy consumption to be 86% for the first floors, 81% for the mid floor and 89% for the last floor. The final energy for heating is slightly increased compared to the standard nZEB scenario, in contrast to the final energy for cooling which is decreased. Shading devices give similar results, but the total final energy consumption is lower in the optimized nZEB scenario. The contribution of Renewable Energy Sources (RES), including solar thermal panels for DHW and PV panels on the roof, ranged between 64 and 79 kWh/m2 for all the apartments. Therefore, the RES cover from 65% to 93% of the primary energy consumption. Table 6. Energy Consumption and CO2 emissions – Optimised nZEB scenario.

Floor

Ap. Unit

First

Mid

Last

Average

Final Primary Energy Final Energy Energy Consumption from Cooling Heating Conventional Sources

Final Energy Consumption

kWh/m2

kWh/m2

kWh/m2

kWh/m2

A

1.4

10.88

19

32.84

Mean Primary Consumption per CO2 emissions Floor kWh/m2

99

Class

kgCO2/m2

Primary Energy RES kWh/m2

5.71

A

76

B

2.27

10.76

34

33.63

9.94

A

64

C

1.34

13.83

25

35.69

7.37

A

79

A

0.43

9.73

14

30.72

4.02

A

76

B

0.82

9.05

11

30.47

3.23

A

79

C

0.31

12.61

19

33.44

93

5.59

A

79

A

1.2

11.29

20

33.05

5.87

A

76

B

2.01

11.13

20

33.74

5.83

A

79

C

1.14

14.26

26

35.92

7.55

A

79

1.21

11.50

21

33.28

6.12

100

76

3.5.2. The payback period The payback periods in the optimised scenario were 3.5 years for the first floor, 5 years for the mid floor and 2.5 years for the last floor. It is observed that the payback period was reduced by 1 year for the first floor, 1.5 years for the mid floor and 2 years for the last floor. 4. Conclusion The study was carried out in order to determine the overall economic viability of the refurbishment of MultiFamily Houses, built before 2007, towards nearly Zero Energy Buildings. To this end, the effectiveness of the energy conservation measures related to the upgrading of the energy performance of the envelope and the energy

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production (PVs) and supply systems (split-units) was evaluated, in terms of energy savings and cost effectiveness. Based on the results a more viable nZEB refurbishment scenario is proposed. The results indicate that the refurbishment of an old Multi-Family House (representative, existing buildings of this typology in Cyprus) into nearly Zero Energy Building, as it is defined by the Directive 366/2014, is financially viable, with payback periods of less than 10 years. From the study it is concluded that the most cost-effective measures for the apartments are the placement of horizontal overhangs, followed by the replacement of the central oil heating, with payback periods less than 1 year. Based on the results obtained from the analysis of the energy and cost effectiveness of the refurbishment measures separately, an alternative refurbishment scenario, which incorporates the most efficient measures which are the placement of horizontal overhangs above the south facing windows and Renewable Energy Sources with larger PV panel area was developed. This scenario highlights the role of PVs in the Mediterranean region, as shown and in previous studies16,17, reducing the payback period up to 2 years, even though the initial cost investment for the optimized nZEB scenario is higher than the standard. Also, taking into consideration the building as a whole, the mean reduction of the CO2 emissions was 292%, compared with its existing state. Moreover, the placement of shading devices presents both an energy efficient and economically viable choice, although not included as an obligatory measure in the requirements of the Directive 366/2014. The minimum requirements towards nearly Zero Energy houses, as drafted by the Cyprus government, especially for the refurbishment of buildings constructed before 1980 result to great energy savings and lower CO 2 emissions. The evaluation of the cost effectiveness and energy efficiency of the different refurbishment measures on the building’s envelope, combined to the high contribution of energy produced from PV systems can lead to the optimization of a refurbishment scenario, in order to constitute a more feasible choice. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

14. 15. 16. 17.

Balaras, Constantinos A., et al. Energy performance of European buildings, ASME 2007 Energy Sustainability Conference. American Society of Mechanical Engineers, 2007. Konstantinou T. & Knaack U. Refurbishment of residential buildings: A design approach to energy-efficiency upgrades. in Procedia Engineering 21; 2011, p. 666–675 Economidou M., et al., Europe’s buildings under the microscope. Performance of Buildings; 2011. San Francisco Planning and Urban Research Association (SPUR). Greening Apartment Buildings Report; 2011, Available Online: . Krukowski A., Andrew & C. Burr., Energy Transparency in the Multifamily Housing Sector; 2012, Available Online: . Cyprus Building Typology, IEE EPISCOPE. at IEE EPISCOPE Project Website: Statistical Service of Cyprus. Typology of the building stock in Cyprus; 2012. IEE EPISCOPE Typology Brochure. Available Online: Ministry of Energy, Cost optimal tool (software), Available Online: Ministry of Energy, iSBEM cy tool, Available Online: Directive 2002/91/EC of the European Parliament and of the Council of 16 December 2002 on the energy performance of buildings, Available Online: < http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex%3A32002L0091> Directive Κ.Δ.Π. 568/2007 Website of the Ministry of Energy, Commerce, Industry and Tourism, Available Online: Ministry of Energy, Κ.Δ.Π. 366/2014, Available Online: Data Hub for the energy performance of the buildings, Available Online: Serghides D. K., et al.. Energy Efficient Refurbishment towards Nearly Zero Energy Houses, for the Mediterranean Region. Energy Procedia 83; 2015, p. 533–543. Serghides D. K., et al., Energy Efficient Refurbishment towards Nearly Zero Energy Terrace Houses for the Mediterranean Region, Mediterranean Green Buildings & Renewable Energy, 2016, In Press.

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