Life cycle costs of nZEBS – CRAVEzero methodology
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The EPBD recast (EPBD recast-European Commission, 2010) established that all new buildings have to reach by the end of 2020 the nZEB target set by the Member States (MS). In order to reach the nZEB targets, while keeping investments sustainable, it is strategic to focus more on the operational phase (Moran, Goggins, and Hajdukiewicz (2017).
The scope of the report D2.2 “Spreadsheet with LCCs – Cost reduction and market acceleration for viable nearly zero-energy buildings” is to provide a CRAVEzero cost spreadsheet, implementing a comprehensive and structured methodology in order to evaluate the LCC with a particular focus on nZEBs.
A data collection template for the evaluation of the nZEB life-cycle costs has been developed as a starting point for the upcoming CRAVEzero LCC tool. The template is structured according to the approach provided by two main sources:
- The Standard ISO 15686-5 (Buildings and constructed assets — Service life planning — Part 5: Life-cycle costing)
- The European Code of Measurement, elaborated by the European Committee of the Construction Economists (CEEC, n.d.).
The first reference provides the main principles and features of an LCC calculation, while the second one describes an EU-harmonised structure for the breakdown of the building elements, services, and processes, in order to enable a comprehensive evaluation of the building life costs.
The tool PHPP (Feist et al., 2012) has been used for the energy performance analysis. This tool summarises all the information dealing with the energy-related features of the building components and services and provides a comprehensive overview of the technologies installed.
Following the ISO 15686-5, the analysis can include different phases of the life cycle, as summarised in Table 1.
|Life cycle processes||INCLUDED costs|
|1. Political decision and urban design phase||Non-construction cost (cost of land, fees and enabling costs, externalities)|
|2. Building design phase||Building design costs|
|3. Construction phase||Construction and building site management costs|
|4. Operation phase||Energy and ordinary maintenance costs|
|5. Renovation phase||Repair and renovation costs|
|6. Recycling, dismantling and reuse phase||Residual value of the elements|
Table 1: Phases and costs in WLC and LCC
The data collection for the CRAVEzero spreadsheet is structured in three parts:
- General project information: it includes the main information of a case study and its context
- Non-construction costs: it deals with the preliminary costs for the WLC and the design phase
- Life Cycle Costs: it reports all the costs for building elements and services during construction and operation, including maintenance and energy costs.
Life Cycle cost calculation
According to the ISO 15686-5:2008, the LCC of a building is the Net Present Value (NPV), that is the sum of the discounted costs, revenue streams, and value during the phases of the selected period of the life cycle. Accordingly, the NPV is calculated as follows:
- C: cost occurred in year n;
- d: expected real discount rate per annum (assumed as 1.51%);
- n: number of years between the base date and the occurrence of the cost;
- p: period of analysis (40 years).
In order to provide a homogeneous and comparable estimation of the energy costs of the case studies, the evaluation is based on the calculated energy demand by using the PHPP evaluation tool (Feist et al., 2012).
In particular, for estimating both the costs and the revenues (due to the renewables installed), we consider the following contributions, in terms of final energy:
- Energy costs:
- Heating demand [kWh]
- Energy demand for domestic hot water production [kWh]
- Cooling demand [kWh]
- Household electricity [kWh] + electricity demand for auxiliaries [kWh]
- Revenues from renewables
- Final energy generated by a photovoltaic system
- Final energy generated by the solar thermal system
The energy produced from renewables is considered in the energy balance as a positive contribution to the energy consumption, and the revenues from the renewable have been discounted from the energy cost. As a general assumption, we assumed a rate of increase of the electricity prices in accounting for 1.0% (calculated from Eurostat values in the CRAVEZero countries).
The analysis within CRAVEzero is based on standard values from EN 15459:2018 that provides yearly maintenance costs for each element, including operation, repair, and service, as a percentage of the initial construction cost. The standard provides a detailed breakdown of the costs for the HVAC, as reported in Table 2. For the passive building elements, an average yearly value accounting for 1.5% of the construction cost has been assumed for the evaluation. The value has been cross-checked with average values coming from the experience of the industry partners.
|Component||Life Span (years)||Annual maintenance (% investment)|
|Air conditioning units||15||4|
|Duct system for non-filtered air||30||6|
|Water floor heating||40||2|
|Heat recovery units||15||4|
|Tank storage for DHW||20||1|
Table 2. Selected maintenance values for building services from the EN 15459:2018
The analyzed case studies are located in different European countries, i.e. Austria, Germany, France, Italy, and Sweden, with specific characteristics in terms of climate conditions, construction, and energy market. Therefore, in order to compare the results of the case studies and to draw a general overview of the costs of the current nZEB practices, a normalization of the collected data is needed. In particular, the construction costs have been normalized considering the data from the ECC (European Construction Costs) that calculated a European construction cost index that quantifies the ratio among the construction costs of EU countries. For the climate conditions, the normalization has been carried out considering the Heating Degree Days of the building locations. Concerning the energy process, a common value has been adopted, accounting for 0,174 €/kWh of final energy consumed.
- EPBD recast-European Commission. (2010). Energy Performance of Buildings Directive 2010/31. EU of the European Parliament and of the Council of, 19
- Moran, P., Goggins, J., & Hajdukiewicz, M. (2017). Super-insulate or use renewable technology? Life cycle cost, energy and global warming potential analysis of nearly zero energy buildings (NZEB) in a temperate oceanic climate. Energy and Buildings, 139, 590–607
- CEEC. (n.d.). Code of Measurement for Cost Planning. Retrieved from https://www.ceecorg.eu/
- Feist, W., Pfluger, R., Schneiders, J., Kah, O., Kaufman, B., Krick, B., Ebel, W. (2012). Passive House Planning Package Version 7. Darmstadt: Rheinstrabe, Germany