Embodied Energy and Nearly Zero Energy Buildings - Science Direct

Available online at www.sciencedirect.com

ScienceDirect Procedia Environmental Sciences 38 (2017) 554 – 561

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

Embodied Energy and Nearly Zero Energy Buildings: A Review in Residential Buildings P.Chastasa,*, T.Theodosioua, D.Bikasa, K.Kontoleona a

Aristotle University of Thessaloniki, Dept. of Civil Engineering, Laboratory of Building Construction and Building Physics, Thessaloniki 54124, Greece

Abstract Towards the EPBD recast 2010/31/EU and the nearly zero energy building (nZEB), this review addresses the whole life cycle energy analysis of residential buildings. Life Cycle Energy Analysis (LCEA) of 90 case studies of residential buildings is evaluated with a specific focus on the normalization procedure that follows the principles of Product Category Rule (PCR) 2014:02 for buildings. The normalization procedure provided a minimization of the sample by considering issues of comparability, the omissions in the boundaries of the system, the LCI method and the updating on the energy efficiency definition of the building. Results indicate that the use of different LCI methods leads to an important fluctuation in the absolute values of embodied energy as the embodied energy of an nZEB calculated with process analysis is lower than every case study calculated with hybrid input-output analysis without including nZEBs. The share of embodied energy in low energy buildings could reach up to 57% -or even up to 83% when renewable energy sources are used for electricity production- and in nZEBs up to 100% even though a significant reduction in the total life cycle energy is identified. The increase in embodied energy and a difference of at least 17% in the share of embodied energy between low energy and nearly zero energy buildings indicate that maybe LCEA should be considered in energy efficiency regulations along with further standardization. ©2017 2017The TheAuthors. Authors. Published by Elsevier B.V.is an open access article under the CC BY-NC-ND license © Published by Elsevier B.V. This (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility ofthe organizing committee of SBE16. Peer-review under responsibility of the organizing committee of SBE16. Keywords:residential buildings;nZEB;LCEA;embodied energy

1. Introduction Towards 2020 and the definition of the nZEB on a national level, according to the EBPD recast 2010/31/EU1

* Corresponding author. Tel.: +30-6976500057 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.2017.03.123

P. Chastas et al. / Procedia Environmental Sciences 38 (2017) 554 – 561

and the regulation 244/20122, member states of the European Union focus on fulfilling these requirements. The increased use of materials led to frameworks and concepts that consider not only the direct energy use but also the total life cycle energy of the building3, by taking into account aspects such as the initial and recurring embodied energy4,5, the transportation of the building’s occupants6 and the choice of materials7. This review examines the total life cycle energy of 90 case studies of residential buildings. The normalization procedure follows the principles of EN 15804:20128, EN 15978:20119, PCR 2014:02 for buildings10 and ISO 14025:200611 in order to provide a common framework for the used metrics and the omissions in the boundaries of the system. The goal of this review is to examine the total energy intensity of residential buildings with a specific focus on the share of embodied energy through the whole life cycle of a building and towards the nearly zero energy building, as indicated also in international literature along with proposals for its standardization6,12-16. Nomenclature nZEB OE EE LCI LCEA LCA PCR EPD PA I-OA H-PA H-IOA RES

nearly Zero Energy Building Operating Energy Embodied Energy Life Cycle Inventory Life Cycle Energy Analysis Life Cycle Assessment Product Category Rule Environmental Product Declaration Process Analysis Input-Output Analysis Hybrid Process based Analysis Hybrid Input-Output Analysis Renewable Energy Sources

1.1. LCA and LCEA Life cycle energy analysis is used for the estimation of the total direct and indirect inputs and outputs of a building’s life cycle. The calculation of embodied energy (manufacturing of materials, transportation, energy for the construction, maintenance, repair, replacement, energy for demolition and end of life management) and the addition of operating energy (cooling-ventilation, heating, lighting, how water and auxiliary systems) in order to expand the boundaries of the system provides the total energy intensity of the building (Fig. 1). Operating energy is defined by regulations on a national and international level. In embodied energy, even though its methodological framework is provided by the LCA method with ISO 14040:200617 and ISO 14044:200618, the LCI method for its quantification varies in the international literature between four main methods: process analysis, input-output analysis, processbased hybrid analysis and input-output hybrid analysis (Table 1). The LCI method appears to provide issues of uncertainty and significant differences in the calculated values of embodied energy with a 64% gap and underestimation between process and hybrid input-output analysis19. Furthermore, in LCEA issues of uncertainty and comparability -such as the boundaries of the system both in operating and embodied energy, the energy metric (primary or final), the year that a study is conducted along with the energy efficiency definition of the building and the functional unit (area and lifespan)- are identified20. In 2014 through the EPD framework PCR for buildings 2014:02, version 01, was published10. PCR is based on ISO 14040 and 14044, EN 15804 and EN 15978, promotes the basic structure and principles of sustainability, provides a common framework for the calculation of LCEA of buildings and appears to be a useful way for the calculation and presentation of LCEA results as indicated in case studies conducted by the same principles20-23.

555

556


Fig. 1. Inputs and outputs in Life Cycle Energy Analysis (LCEA). Table 1. Life Cycle Inventory (LCI) methods. LCI Method

Data

Benefits

Problems and limitations

Process Analysis

physical

oldest and most used method

incompleteness24,25, limited boundaries of the system→ uncertainty26, truncation error→ underestimation of EE25,27,28

Input-Output Analysis

Process-based Hybrid Analysis

financial

physical & financial

systemic completeness in reference to process analysis29 reduces the truncation error

32

“black box” with limited application29, aggregation error25,30,31 financial data→ aggregation error32, incomplete process data, product prices & energy tariffs →increased sensitivity24,33, sideways and downstream truncation errors27,29,

Input-Output Hybrid Analysis

physical & financial

disaggregation of I-O model33,

exclusion of capital input data27

follows direct energy paths and avoids indirect effects31,33,34, “remainder”→ reduces sideways and downstream truncation error29, limitation of time31,33,34

Literature reviews in the past have applied a normalization procedure to overcome issues of uncertainty and comparability35-37. These issues are addressed by the current review with a normalization procedure that is based on the principles and framework of PCR 2014:02.


2. Methods 2.1. Case Studies The case studies of residential buildings were selected with no geographical limitations applied and the final sample consisted of 90 case studies20. Although a larger sample is available in the literature, restrictions had to be addressed in order to achieve comparability through the normalization procedure. The use of primary energy as a metric in the calculations and the clear statement in the boundaries of the system, the lifespan, the area of the building and the LCI method were the addressed criteria for the selection of case studies. Nevertheless, a small number of case studies that would expand the geographical limits and fulfill the requirements of this review were retained in the sample. The majority of the examined case studies appear to have a lifespan of 50 years and are located after the year 2010 (Fig. 2).

Fig. 2. Year of the study and lifespan (in years) of the 90 LCEA case studies of residential buildings.

2.2. Normalization Procedure In order to overcome issues of uncertainty and comparability, a normalization procedure was applied to the initial data and results of the 90 case studies. The normalization was conducted by following the framework of PCR 2014:02 and by applying an update on the energy efficiency definition of the building case studies in order to provide comparability through time and between different energy efficiency requirements. The normalization is defined by two steps (Table 2): x Step 1. In a first approach, criteria are applied only to the functional unit, the energy metric and the energy efficiency definition of the building. For the low energy and the passive house definition, the option of the primary energy demand limit (Qp≤120 kWh/(m2·a),) for the transitional phase provided by the Passive House Institute is used, with the -available in each case study- remaining parameters following the updated values defined in 201538.

557

558


x Step 2. In a second step of the procedure, further limitations are applied to the processes of the LCEA boundaries of each case study in order to provide comparability and increase the homogeneity of the sample. Table 2. Analysis of the normalization procedure. Normalization Criterion Functional unit

Defined parameters-1st step Lifespan : 50 years

10

Defined parameters-2nd step Lifespan : 50 years10

Area: net heated floor area (Atemp)10 10

Area: net heated floor area (Atemp)10 Primary energy in MJ10

Energy metrics

Primary energy in MJ

Embodied energy-processes

Upstream (A1-A3), core (A4-A5) and downstream processes (B1-7&C1-4) as defined in PCR 2014:02

Building energy efficiency definition

low energy: QP ≤ 120 kWh/(m2·a), heating demand≤30 kWh/(m2·a), cooling and dehumidification demand≤ Passive House Requirement + 15 kWh/(m2·a), Pressurization test result n50≤1.0 1/h38,

Exclusion of case studies that do not include transportation processes (A2&C2), waste processing (C3) and disposal (C4)20

passive: QP ≤ 120 kWh/(m2·a), heating demand≤15 kWh/(m2·a), cooling and dehumidification demand≤15 + dehumidification contribution kWh/(m2·a), Pressurization test result n50≤0.6 1/h38, nZEB: defined by the energy balance of the building and by the national reference limit values39, conventional: QP >120 kWh/(m2·a) Operating energy-processes

No restrictions or limitations

Exclusion of case studies that do not take into account energy for lighting and auxiliary systems20

After the normalization, the embodied energy (EE-in MJ) is calculated as the difference between the total life cycle energy (LCE-in MJ) and the operating energy (OE-in MJ) of the building (Eq.1), as a simplified approach40-42:

EE

LCE OE

(1)

In a final step, the share of embodied energy ( in %) in the total life cycle energy is calculated for each case study. It must be stated that possible declination from the accurate results of the cases studies due to the extraction of data from charts and graphs -when not available in table form- should not be ignored. 3. Results 3.1. Normalization procedure- 1st step The results indicate that the share of EE in residential buildings varies between 5% and 100%. In conventional buildings, this share ranges between 5% and 36% and in low energy buildings between 23% and 58% except for a small number of extreme values as indicated in Fig. 3.a. Despite the decreased energy consumption in low energy buildings, the extremely high values of OE could be justified by the effect of the recycling potential, by a simplified approach and exclusion of end of life processes in the calculation procedure or even by the building methods and materials used20. In low energy buildings the significant high share of EE -and low share of OE respectively- could be explained by the use of renewable energy sources (RES) for the production of electricity and by the limited processes taken into account in the use phase of the building’s life cycle20. In passive buildings, the share of EE could reach up to 57% except from an extreme value (79%) of a case study with RES used for electricity production20. In nearly zero energy buildings, EE dominates with a share that could reach up to 100% and a minimum value of 69% that reaches the case studies of low energy and passive buildings with electricity production. Significant differences are identified in the calculated values of EE deriving from the LCI method used in each case study of the initial sample (90 LCEA case studies). The normalization results indicate that the absolute value of embodied energy calculated with hybrid analysis (process-based or input-output) for a conventional building is higher almost than every case study calculated with process analysis and reaches the process analysis calculated values of the nZEB case studies (Fig. 4).


Fig. 3. The share of embodied energy (EE in %) for the LCEA case studies of residential buildings. (a) Normalization procedure-1st step-90 LCEA case studies of residential buildings, (b) Normalization procedure-2st step-39 LCEA case studies of residential buildings.

Fig. 4. Embodied energy (EE in GJ/m2) for the 90 LCEA case studies of residential buildings and for the different LCI methods.

3.2. Normalization procedure- 2nd step In the second stage of the normalization procedure a number of limitations were applied (Table 2). By applying the limitations the final sample was minimized to a number of 39 LCEA case studies and consists only of case studies calculated with process analysis even though this was not a limitation or intention of this procedure. Although this outcome results to a homogeneity in the final sample it does not provide any correction or reduction in the underestimation of EE and in the potential truncation error deriving by the use of process analysis. The results in the final sample indicate a share of EE in conventional buildings between 6% and 20% and in passive between 11% and 33% (Fig. 3.b). In low energy buildings, the share of EE ranges between 26% and 57% with a significant difference of 17% from the lowest value (74%) of an nZEB. In nZEBs, the share of EE could reach up to 100% when zero balance is achieved.

559

560


4. Conclusions and Discussion The fluctuation in the metrics, the omission in the boundaries of the system and the calculation methods in LCEA indicates the importance of comparability when a review is conducted. A normalization procedure that follows the principles of standards8-10 provides a clear presentation of the data, with no further limitation of uncertainty in the calculation procedure and results20. The uncertainty of the LCI method appears to be significant in the calculation of embodied energy, with an average value almost 4.00 times higher when hybrid I-O analysis is used instead of process analysis, as indicated also in the literature with a respective value of 3.7819,43,44. An initial sample of 90 and a final minimized sample of 39 LCEA case studies of residential buildings was examined in the current review. The share of embodied energy appears to increase towards the nZEB even though an important reduction up to 50% in the total energy intensity of the building is identified20. The share of EE in conventional buildings ranges between 6%-20%, with a similar range of 10-20% also identified in a previous review36. In low energy buildings, the share of EE varies between 26-57%. Previous reviews indicate a share of embodied energy for conventional and low energy buildings that ranges between 2% and 46% 37 and 5,1% and 42,4%35 that appears to be close to the range of the current review. In passive buildings, the share of EE varies between 11% and 33% with a respective value of 13,1% also indicated in previous case studies19. The use of RES in low energy or passive buildings appears to increase the share of EE in the range of an nZEB that varies between 74% and 100%. A 17% gap is identified in the share of EE between nZEB and low energy buildings with an increase up to 54% between the nZEB and conventional buildings. The increase in embodied energy indicates by the that maybe LCEA should be considered in energy efficiency regulations along with its further standardization.

Acknowledgements This review was funded by the Greek State Scholarship Foundation/IKY and SIEMENS. It was conducted in the framework of the “Research Project For Excellence IKY/SIEMENS” and for the research project “Investigation of the effect of embodied energy in nearly zero energy buildings-nZEB, in the context of EPBD recast/2010/31/EE and the regulation 244/2012 of the European Union”.

References 1. Union EPaCotE. Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast). Official Journal of the European Union 2010. 2. Commission E. Guidelines accompanying Commission Delegated Regulation (EU) No 244/2012 of 16 January 2012 supplementing Directive 2010/31/EU of the European Parliament and of the Council on the energy performance of buildings by establishing a comparative methodology framework for calculating cost-optimal levels of minimum energy performance requirements for buildings and building elements. Official Journal of the European Union; 2012. 3. Hernandez P, Kenny P. From net energy to zero energy buildings: Defining life cycle zero energy buildings (LC-ZEB). Energy and Buildings. 2010;42(6):815-821. 4. Cellura M, Guarino F, Longo S, Mistretta M. Energy life-cycle approach in Net zero energy buildings balance: Operation and embodied energy of an Italian case study. Energy and Buildings. 2014;72:371-381. 5. Crawford RH, Czerniakowski I, Fuller RJ. A comprehensive framework for assessing the life-cycle energy of building construction assemblies. Architectural Science Review. 2010;53(3):288-296. 6. Stephan A, Crawford RH. A multi-scale life-cycle energy and greenhouse-gas emissions analysis model for residential buildings. Architectural Science Review. 2013;57(1):39-48. 7. Rosselló-Batle B, Ribas C, Moià-Pol A, Martínez-Moll V. An assessment of the relationship between embodied and thermal energy demands in dwellings in a Mediterranean climate. Energy and Buildings. 2015;109:230-244. 8. Institution BS. EN 15804:2012 - Sustainability of construction works. Environmental product declarations. Core rules for the product category of construction products. BSI; 2012. 9. Institution BS. EN 15978:2011 - Sustainability of construction works. Assessment of environmental performance of buildings. Calculation method. BSI; 2011. 10. Tyréns A. Product category rules according to ISO 14025:2006 Product group-2014:02. 2014-02-26 valid until 2017-02-26 2014. 11. Organization I. ISO 14025:2006 - Environmental labels and declarations - Type III environmental declarations - Principles and procedures. //

P. Chastas et al. / Procedia Environmental Sciences 38 (2017) 554 – 561 2006. 12. Casals XG. Analysis of building energy regulation and certification in Europe: Their role, limitations and differences. Energy and Buildings. 2006;38(5):381-392. 13. Crawford RH, Czerniakowski I, Fuller RJ. A comprehensive model for streamlining low-energy building design. Energy and Buildings. 2011;43(7):1748-1756. 14. Oregi X, Hernandez P, Gazulla C, Isasa M. Integrating Simplified and Full Life Cycle Approaches in Decision Making for Building Energy Refurbishment: Benefits and Barriers. Buildings. 2015;5(2):354-380. 15. Balouktsi M, Lützkendorf T. Energy Efficiency of Buildings: The Aspect of Embodied Energy. Energy Technology. 2016;4(1):31-43. 16. Lützkendorf T, Foliente G, Balouktsi M, Wiberg AH. Net-zero buildings: incorporating embodied impacts. Building Research & Information. 2014;43(1):62-81. 17. Organization I. ISO 14040:2006 - Environmental management - Life cycle assessment - Principles and framework. // 2006. 18. Organization I. ISO 14044:2006 - Environmental management - Life cycle assessment - Requirements and guidelines. // 2006. 19. Crawford RH, Stephan A. The Significance of Embodied Energy in Certified Passive Houses. International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering,World Academy of Science, Engineering and Technology. 2013;7(6):427-433. 20. Chastas P, Theodosiou T, Bikas D. Embodied energy in residential buildings-towards the nearly zero energy building: A literature review. Building and Environment. 2016;105:267-282. 21. Blengini GA, Di Carlo T. The changing role of life cycle phases, subsystems and materials in the LCA of low energy buildings. Energy and Buildings. 2010;42(6):869-880. 22. Takano A, Pal SK, Kuittinen M, Alanne K. Life cycle energy balance of residential buildings: A case study on hypothetical building models in Finland. Energy and Buildings. 2015;105:154-164. 23. Zabalza I, Scarpellini S, Aranda A, Llera E, Jáñez A. Use of LCA as a Tool for Building Ecodesign. A Case Study of a Low Energy Building in Spain. Energies. 2013;6(8):3901. 24. Treloar GJ. A Comprehensive Embodied Energy Analysis Framework: Faculty of Science and Technology, Deakin University; 1998. 25. Lenzen M. Errors in Conventional and Input-Output—based Life—Cycle Inventories. Journal of Industrial Ecology. 2000;4(4):127-148. 26. Hendrickson C, Horvath A, Joshi S, Klausner M, Lave LB. Comparing Two Life Cycle Assessment Approaches: A Process Model- vs. Economic Input-Output-Based Assessment Paper presented at: IEEE International Symposium on Electronics and the Environment1997. 27. Crawford RH. Validation of a hybrid life-cycle inventory analysis method. Journal of environmental management. Aug 2008;88(3):496-506. 28. Majeau-Bettez G, Stromman AH, Hertwich EG. Evaluation of process- and input-output-based life cycle inventory data with regard to truncation and aggregation issues. Environmental science & technology. Dec 1 2011;45(23):10170-10177. 29. Treloar GJ. Environmental assessment using both financial and physical quantities. Paper presented at: Proceedings of the 41st Annual Conference of the Architectural Science Association ANZAScA2007; Geelong. 30. Miller RE, Blair PD. Foundations of Input-Output Analysis. Prentice-Hall, Englewood Cliffs, NJ; 1985. 31. Crawford RH. Using Input-Output Data in Life Cycle Inventory Analysis, Deakin University; 2004. 32. Bullard CW, Penner PS, Pilati DA. Net energy analysis. Resources and Energy. 1978/11/01 1978;1(3):267-313. 33. Treloar GJ. Extracting Embodied Energy Paths from Input–Output Tables: Towards an Input–Output-based Hybrid Energy Analysis Method. Economic Systems Research. 1997;9(4):375-391. 34. Treloar GJ, Love PED, Holt GD. Using national input/output data for embodied energy analysis of individual residential buildings. Construction Management and Economics. 2001;19(1):49-61. 35. Karimpour M, Belusko M, Xing K, Bruno F. Minimising the life cycle energy of buildings: Review and analysis. Building and Environment. 2014;73:106-114. 36. Ramesh T, Prakash R, Shukla KK. Life cycle energy analysis of buildings: An overview. Energy and Buildings. 2010;42(10):1592-1600. 37. Sartori I, Hestnes AG. Energy use in the life cycle of conventional and low-energy buildings: A review article. Energy and Buildings. 2007;39:249-257. 38. Institute PH. Criteria for the Passive House, EnerPHit and PHI Low Energy Building Standard. Darmstadt, Germany: Passive House Institute;2015. 39. Boermans T, Grözinger J, Ashok J, Seehusen J, Wehringer F, Scherberich M. Overview of Member States information on NZEBs - Working version of the progress report - final report. 08/10/2014 2014. BUIDE13705. 40. Berggren B, Hall M, Wall M. LCE analysis of buildings – Taking the step towards Net Zero Energy Buildings. Energy and Buildings. 2013;62:381-391. 41. Gustavsson L, Joelsson A. Life cycle primary energy analysis of residential buildings. Energy and Buildings. 2010;42(2):210-220. 42. Horne R, Opray L, Grant T. Integrating Life Cycle Assessment into housing environmental performance assessment. Paper presented at: 5th Australian Conference on Life Cycle Assessment2006; Melbourne Australia. 43. Stephan A, Stephan L. Reducing the total life cycle energy demand of recent residential buildings in Lebanon. Energy. 2014;74:618-637. 44. Crawford RH. Life cycle assessment in the built environment. London: Spon Press; 2011.

561