Building life cycle optimization tools for early design phases

Energy xxx (2015) 1e11

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Building life cycle optimization tools for early design phases Iva Kovacic*, Veronika Zoller Department for Industrial Building and Interdisciplinary Planning, Vienna University of Technology, Karlsplatz 13, 1040 Vienna, Austria

a r t i c l e i n f o

a b s t r a c t

Article history: Received 25 November 2014 Received in revised form 6 March 2015 Accepted 7 March 2015 Available online xxx

The early building design phases play crucial role for the determination of building's life cycle performance in terms of resources and energy consumption and development of LCC (life cycle costs). In this stage the optimization potential is still very large, at very low cost. In the latter planning phases the change possibility rapidly decreases with simultaneously increasing costs. The investors and planners are increasingly requiring design tools as decision support instruments, which would enable simulation and optimization of LCC already in the early planning phases. This paper will present a comparative study of three commercial software-tools for LCC-calculation, and test their fitness for the implementation in the early design phases. Using a Case Study of an energy efficient building, LCC were assessed employing the three tools and the deviations of the results were compared. The analysis showed, that the tested tools cannot be employed in the early design phases without adoption and customization, lacking of benchmarks and extensive data representing the largest problem for a reliable LCC calculation and optimization. In further step, a strategy for investors for the assessment of LCC in the architectural competitions as decision support was developed and verified on a real-life project. © 2015 Elsevier Ltd. All rights reserved.

Keywords: Life cycle costs Simulation Cost calculation Life cycle optimization

1. Introduction 1.1. Research motivation Buildings consume energy and resources, as well as financial assets throughout the whole life cycle, causing not only significant environmental but economic impact as well. The issue of affordability is increasingly gaining on significance in the context of sustainability [1]. Literature implies that one of the main obstacles in reaching the EBPD (Directive on the energy performance of buildings) [2] aims in achievement of nearly zero energy buildings are the investment costs for technology and construction [3,4]. Therefore, a decision-making framework for the investors, allowing assessment of not only costs, but also of life-cycle savings and benefits is

List of Abbreviations: CG, cost group; CS, costs for construction structure; CE, costs for construction engineering (HVAC); CF, costs for construction finishing; CC, construction costs (CS þ CE þ CF); EC, energy cost; OC, operational costs (energy, water, utilities, cleaning); MSC, maintenance and service cost; RC, regular costs (OC þ MSC); IC, irregular costs (replacement, renewal), occurring after expired expected life duration of an element or component; DC, costs for demolition or disposal; FC, following cost (RC þ IC); LCC, discounted present value of CC þ FC þ DC; BIM, building information modelling. * Corresponding author. Tel.: þ43 1 58801215 26. E-mail addresses: [email protected] (I. Kovacic), veronika.zoller@gmail. com (V. Zoller).

necessary, moving the focus from the decision-making based exclusively on the construction costs towards life cycle costs [5,6]. The aim of this paper is to extend the existing body of knowledge on LCC (life cycle cost) analysis for energy efficient buildings. The LCC approach has been widely used by the academics for the evaluation of the building energy supply and energy systems, yet seldom using the building design approach and incorporation construction costs and relevant standards. The novel approach introduced in this paper is building design-oriented LCC analysis in the earliest, for future life cycle building performance crucial design stages, when low-resolution design information is available, using the obligatory standards for cost assessment. The early planning phases (programming and pre-design) play crucial role for the future performance of a building throughout the life cycle e here the optimization potential is almost infinite, at a very low cost. Bogenst€ atter points out, that early design stages determine up to 80% of building operational costs, as well as of environmental impacts [7]. In the latter planning phases the change-possibility rapidly decreases with simultaneously increasing costs (Fig. 1). The operational costs exceed the construction costs by a multiple; whereas the exact exceeding point as well as the ratio of initial to following costs depends on the quality of construction, the use-intensity and the building-type, as well as on considered life duration. Both academic research and industry claim that integrated planning process, including life cycle costing

http://dx.doi.org/10.1016/j.energy.2015.03.027 0360-5442/© 2015 Elsevier Ltd. All rights reserved.

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Fig. 1. Cost development vs. change potential over building life cycle [10].

and optimization can significantly decrease the following costs [8,9]. The application of LCC analysis allows early assessment of the operational saving potentials or compilation and evaluation of variant-study [8] (Fig. 2). However, the AEC industry is facing a problem, which has already been known from other industries, that the early planning phases are characterized by lack of information, data and tools [11]. Therefore, investors and planners are increasingly requiring planning tools as decision support instruments, which would enable simulation and optimization of life cycle costs already in the early planning phases (pre-design). 1.2. Life cycle costing in construction: state of the art The whole life cost or whole lifecycle costing e as a total cost of ownership over the life span of a building is despite a long history

of more than 40 years, a still relatively novel approach in the AEC industry. Before the 1970s the decision-making in construction was solemnly made upon capital costs. The first movement which questioned this approach, advocating the benefits of higher capital investments for better value in the operation was so called “terotechnology” [12]. This movement was followed by the organized data assessment for the actual operation of the buildings, initiated in 1971 by RICS. In the 1970s the thought of optimization of running costs arises and appears in literature, such as cost-in-use, only in the late 1970s the LCC methodology appears. However, its practical implementation is hindered by the lack of reliable data. Finally, in the year 2000 the ISO 15686 [13] appears defining LCC, as well as the principle of whole life costs (also whole lifecycle costing) for management of long term cost assessment of capital projects [12]. Outside of the AEC industry, the lifecyclecosting methodology was largely applied by the US Department of

Fig. 2. Whole life cycle costs, after ISO 15686 [13].

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Defence for procurement, as well as by the Australian Defence, since the mid-1980s [12,14]. Even though the methodology is well developed and standardized by now, it is still facing numerous problems in the practice. Lack of reliable data and benchmarks as well as the data accessibility is the most common problem for the planners. Gluch and Baumann [14] criticise the suitability and usefulness of the LCC method of the environmentally responsible capital projects, where the external costs are largely neglected, as well as the decision making under uncertainty. In order to overcome these obstacles, the combined approach using both lifecyclecosting and life cycle assessment is advocated by researchers [15,16]. Further issue represents the multiple stakeholder-perspective, where the aims of lifecyclecosting largely diverge for different stakeholders. The interest of building owners is the optimization of the costs for which they are responsible (maintenance, replacement), which is not necessarily the shared interest of the tenants (low energy costs). The intentions for carrying out of a life cycle costs analysis also diverge e motivations can range from solemnly construction cost reduction, reduction of rental strains, reduction of maintenance costs, optimization of investment, variant studies, long term budgeting, cost controlling, building certification etc. The aims have a large impact on the choice of method, the duration period and the cost groups to be analysed. Ellingham and Fawcett [17] claim that sustainable development requires sustainable investments, meaning the ones maximising the benefits in relation to the used resources. They identify the under- or over-investment, where under-investment chooses the cheaper solution which consumes large amount of resources in the future; whereas in the over-investment a high-level investment is made in expectation of future high benefits, however these turn out lower than expected. In both cases resources are used up in nonefficient, non-sustainable way. The authors argue that a whole life-cycle costing method based on future options or alternative strategies is a proper way to identify efficient investment, thus contributing to the sustainable development.

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efficiency of buildings (prevailing the residential), there are gaps in the research of LCC analysis in the building sector. The formerly presented research is optimizing pre-defined building designs through either variation of technology or singular aspects such as building hull quality, and is in this sense re-active. A design-oriented exploration of LCC analysis for holistic assessment of building life cycle costs in the earliest design stages; based on the normative framework for the LCC assessment as pro-active tool is lacking. Considering all of the previously mentioned issues, public investors are obliged to meet the aims of sustainable building, simultaneously facing limited financial means, and often very rigid institutional framework as well as the procurement procedures. Finding of the balance between the level of energy efficiency, and life cycle costs and benefits represents a challenge for decision making process. Therefore, in order explore the LCC analysis for decisionmaking support in the earliest design stages, a comparative study of three commercial software-tools for the calculation and analysis of life cycle costs was carried out. In a Case Study for pre-design for an energy efficient office building, the three tools were tested and evaluated. The analysis showed, that the tested tools can not be employed in the early design phases without adoption and customization, lacking of benchmarks and reliable data representing the largest problem for a life cycle cost calculation and optimization. In further step, a strategy with LCC analysis method for investors primarily, but also planners as decision support tools in the early design stages was developed. Through application of the method on real-life architectural competition was shown, that the most energyefficient design does not necessarily result with the minimum of life cycle costs. Further research is necessary for determining of exact break even point in achievement of economic and energy-efficiency optimum, as well as closer investigation of further factors influencing the LCC (e.g. building and design quality, life duration). 2. Life cycle costing methodology and normative 2.1. LCC methodology

1.3. Research gaps and research objectives The life cycle cost and benefit methodologies as currently used in building and construction industry are mostly implemented for economic evaluation of specific, mostly technological aspects, and not for the holistic evaluation of a building as a system of construction, technology and function. Lutz et al. [18] apply LCC analysis for energy-efficiency design options for residential furnaces, Milan et al. [19] analyse cost-efficiency of residential energy supply systems, Cui et al. apply [20] LCBA for storage systems for buildings; where exclusively the energy systems and technologies are analysed and buildings are only represented as the demand side. Marszal and Heiselberg [4] include in their analysis of NEZEB residential building the construction costs, but in very generalised manner, main focus is on the LCC analysis on variations of building energy service systems, such as PV and district heating. Sorsak et al. [21] analyse the economic efficiency of an energy-optimized timber family house, simulated by Passive House Planning Package, however with particular focus on the building hull quality and energy systems; finding the optimum between the energy efficiency and economic feasibility. Even though this approach is design-oriented, it does not considering building as a whole, but focussing on the singular aspect of optimization of building hull. Kneifel [6] is one of the few authors who analyses a large number of non-residential buildings in terms of life-cycle costing and life-cycle assessment; by using prototypical buildings as type representatives and running thermal simulations for the types; thereby varying analysis periods. Despite the developed body of knowledge and joint efforts of advancing the life-cycle analysis for advancement of energy-

The life cycle cost assessment can be considered as a part of the economic feasibility study, proving economic success of a real estate, as well as the resources-efficiency. In general, the methods for accounting of life cycle costs (also of cost-efficiency studies) can be differentiated in static or dynamical methods. The static methods view only a specific point in time or time-period, thus not valuing the time e the different value of money at different points of time is not considered. Since buildings require investments through out the life cycle, the static methods are less suitable since they view only a specific point in time e for assessment of the whole life costs dynamic methods are necessary [22]. Since future investments will occur at a future point in time, the values have to be discounted in order to enable comparability with todays’ values. The net present value is the value of a future investment at the current point of time e “how much money would have to be invested currently, at a given rate of return, to yield the cash flow in future.” [23]. This is a value of an investment which would have to be placed at a given discount rate in order to have latter returns. The net present value of a future investment is calculated by the formula (1):

C0 ¼

T X

Ct

t¼0

ð1 þ iÞt

(1)

C0…… Net present value Ct……. Sum of all payments t……… Current point in time

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T…….. Time horizon (50 yrs) i……… Discounting rate (5.5%) The amount of the net present value depends on the future investments and discounting rate. The actual composition of the discounting rate is a matter of ongoing discussion amongst academics and practitioners. Woodward [24] identifies the most common methods for determining of the discounting rate:  the current or expected rate the organisation must pay for the use of its borrowed funds;  the rate of return that could be expected from the loaning of money, but which is denied to the organisation by the need to fund its own projects (sometimes referred to as the opportunity cost);  the lowest rate of industrial borrowing. For the assessment of life cycle costs this means that the construction costs are the nominal value, which is due at the beginning of the life duration. The costs for maintenance, inspection or cleaning have to be discounted to the nominal time, meaning the end of construction. The discounted cash flow method has often been criticised for suitability for assessment of whole life costs in relation to sustainability, due to the uncertainty of the parameters which are largely based on assumptions. The assumptions for the inflation rate, energy price increase, etc. have huge impact on the final result. For dealing with uncertainty, methods such as uncertainty assessment, scenario development and similar can be applied [17]. As parameters which increase uncertainty can be identified:  Time horizon (assumptions on life duration) e the longer the lifetime, the more importance gain the following costs. The assumptions related to the life duration are of crucial importance, since the results largely differ for the life horizons of 20, 50 or 80 years. Most of the guidelines recommend/use the life horizon of 50 years [8]. In the projects with longer technical life duration or in refurbishment-projects more probable is a longer time horizon of 80 years. However, the increasing length of time horizon also increases the uncertainty of the development of following or operational cost [25].  Price increase (development) e whereas the costs related to labour (cleaning, administration) are relatively simple to predict, the prognosis of the energy price development is much more difficult and highly uncertain.  Discounting rate e is based on the assumption or experience of the investor or financing consultant and is therefore always subjective. As benchmarks can be used minimal nominal yield of investor or cost rate of borrowed funds [26]. The choice of a discounting rate has large impact on the LCC results e the discounting of the future payments reduces the importance and impact of the operational costs. The payments that lie far in the future can nearly loose on the meaning depending on the choice of discounting rate [27]. A discounting rate of 0% corresponds to a static calculation. In this research the data by Statistik Austria was used, which provides the Construction Cost index [28] as well as the consumer price index as benchmark for general price development and inflation. For the assumption of the discounting rate, the interest rate for Austrian government stocks was used. 2.2. Standards The life cycle costs of buildings are in the meanwhile regulated by a great number of various international and national standards

and guidelines for assessment of life cycle costs. On the international level, the most significant standard is the ISO 15686 [13]; € whereas in the German speaking region these are the ONORM B 1801-2 [29] in Austria and DIN 18960 [30] in Germany. 2.2.1. ISO The ISO 15686 differentiates between the “narrow life cycle cost approach, where only the cost side (investments) is assessed, whereas the life cycle cost calculation in more broader sense assesses the costs as well as the benefits (returns) e WLC (wholeelife cycle costing). The WLC can also be seen as investment calculation, or as life cycle success. In this paper only the cost side of the LCC will be assessed (LCC in the narrow sense). In general, the LCC can be split into two main areas e the construction cost and the following cost. In the meanwhile, both areas are defined by different standards, which facilitate the assessment, the comparison of the variants and benchmarking process. € 2.2.2. Austrian standard: ONORM B 1801-2 € The Austrian standard ONORM B 1801 e the project management in construction standard e defines both construction and life € cycle costs. The first part, ONORM B 1801-1 [31], defines the con€ struction costs. The second part, ONORM B 1801-2 [29], serves as basis for the prediction of the utilization costs of buildings. The € ONORM B 1801-2 is a second part of the standard (Table 1). The standard defines the LCC as “sum of the discounted con€ struction costs acc. to ONORM B 1801-1 and following costs”, whereas the following costs are defined as the „sum of all discounted costs resulting from the use and operation of the building together with the demolition and disposal costs and are related to the project or to the one or several elements according to the € system of ONORM B 1801-1”. 2.2.3. German standard: DIN 18960 For cost estimation in building construction, particularly finding and structuring of costs, the DIN 276-1 [32] is being used. This German standard includes the costs of new constructions, modification and refurbishment of buildings as well as the contiguous project-oriented costs. € The German counterpart to the ONORM B 1801-2 is DIN 18960 [30] e following costs in construction (Table 1). Following costs acc. to the DIN 18960 are “all regular and irregular costs in construction and site from the beginning of their usefulness till demolition” [16]. Table 1 displays comparison of the Austrian cost standard with the German DIN standard e systematization of DIN Standard is € largely differing from ONORM, e.g. completely lacking the cost group “demolition”, which has to be considered when working with tools using different standards e a mix of data can represent a considerable obstacle. 3. Tools for LCC in the early design stage The main challenge for sustainable design is how to implement the economic and ecologic optimization in the early design stages, because design-decisions reached at this point are determining the whole life-performance of the building. In general, the assessment of life cycle costs in the early design stages is based on the topdown approach, using reference values of similar building typologies for calculation of construction and following costs, which are mostly obtained through regression analysis of existing building data or aggregation of building elements [9]. The same methodology applies to the estimation of life durations. A further approach for the estimation of life cycle costs is application of averaged values as percentage of construction cost as yearly regular payments. Thereby the construction costs and life-duration of building

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Table 1 € Comparison of ONORM B 1801-1 and -2 [29,31] and DIN 276-1 and DIN 18960 [32,30]. Construction cost (CC) cost groups

€ ONORM B1801-1

Construction cost (CC) cost groups

DIN 276-1

0 1 2 3 4 5 6 7 8 9 Following costs (FC) cost groups 1 2 3 4 5 6 7 8 9

Ground Ground development Construction structure CC Construction engineering CE (HVAC) Construction finishing CF Interior Outside facilities Planning work Supplementary work Reserve € ONORM B1801-2 Administration Technical operation of building Supply and disposal Cleaning and cultivation Security services Facility services Overhaul Other costs Removal and demolition

100 200 300 400 500 600 700

Ground Ground development Construction structure Construction engineering Outside facilities Fittings and artwork Supplementary costs

Following costs (FC) cost groups 100 200 300 400

DIN 18960 Capital costs Construction management costs Operational costs Maintenance

elements are used as basis for the calculation of the depreciation or re-investments through out the building life-cycle [7]. The issue of referential values remains one of the largest problems for the LCCassessment, since the data is seldom reliable (black box) and if available, then very costly. LCC assessment uses discounted cash flow method, as mentioned, for the calculation of net present value of the life cycle costs. LCC in general are composed of initial investment (usually construction costs) plus the following costs, consisting of regular payments such as: energy, utilities, cleaning and maintenance; and irregular costs for renewal or replacement, occurring after expiration of technical life duration of an element or system. Some LCC methods also include the costs for demolition. In order to enhance the use of life cycle costing methodology for optimization of design amongst planners and investors, several tools available at German speaking market were tested on a Case Study of an energy efficient building for application-fitness in the earliest design phases. Thereby the following tools were tested:  LCC Indicator number 16 by the DGNB/BNB building certificate [33e35];  ABK LEKOS Software [36];  LEGEP Software [37].

The DGNB/BNB indicator 16 is prescribing a calculationmethodology, which is basically assessing the LCC as discounted present value of: chosen investment costs (construction and HVAC), regular costs (water, waste, energy, cleaning, service and maintenance) and irregular costs (replacement of construction or HVAC elements according to life duration), using pre-set conventions (discounting rate, price increase, energy-price increase, time horizon of 50 years). The costs for disposal are not included in the calculation. An excel-tool for LCC assessment is available at the BNB web site [34], which can also be easily adapted for specific project-purposes. The excel sheet consists of two parts e one part with the pre-set tables for input of the data, and the other part with the graphical representation of results. The payments are split in two main groups: regular and irregular payments. Representative for the irregular payment is e.g. replacement of building elements after the expiration of specific life duration, whereas regular payments occur yearly. Regular payments include: supply and waste, cleaning, inspection and service of building elements and HVAC (calculated as yearly % of CS, respectively CE or CF). Irregular payments include: initial investment for construction and HVAC, replacement costs for construction and HVAC after expiration of expected life duration. The obtained results are consequently compared to the referential values of the certificate; credits are awarded according to the level of achievement of referential values.

3.1. DGNB/BNB indicator 16: LCC 3.2. ABK LEKOS software The German Council for Sustainable Building [33], as well as the Austrian equivalent, the Austrian Sustainable Building Council [38], certificate is based of five pillars: economic, ecologic, social, technical and process quality aspects for assessment of sustainability of existing or new construction. Within the economic pillar the assessment of LCC is obligatory. The public version of the certificate is a so called BNB certificate (Assessment System Sustainable Building for Federal Buildings) [34]; by German Federal Ministry for Environment, Nature Conservation, Building and Nuclear Safety, the documentation for which is obtainable at the web site. The life cycle costs are described in the indicator 16: Life Cycle Costs [35], which consider only the chosen cost groups. Therefore the LCC using this method can largely differ from the investmentor bankability-based assessment. The use of this indicator can be primarily seen for comparative purposes, comparing two buildings or of one building matching to the prescribed benchmarks.

The LEKOS tool [36] is set up upon the ABK cost estimation and calculation tool, which has been present on the Austrian market for € € thirty years. The tool is based on ONORM B 1801-1 and ONORM B 1801-2 structure for the calculation. A basic data-base is included in the software and the cost groups include all of the costs from site till reserves. Some of the costs can be extracted from the provided database, the others are calculated via factor (e.g. the costs for the excavation pit). This method is suitable for the early design, however insufficiently accurate for the latter phases. 3.3. LEGEP software LEGEP [37] was developed within a research project exploring integrated design of sustainable buildings. It is based on analysis of

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various flows, such as monetary-, material-, resources- and energyflows along the life cycle. It includes extensive database on costs, life cycle costs and environmental data of building elements. The software consists of several modules, each of which is related to own database: project, cost planning, energy, cost efficiency, life cycle costs, ecology, comparison of building elements. The databases with characteristic LCC data used for the modules are: sirAdos-Baudaten [39], BNB e Useful life duration of building ele€ ments [34], Okobau.dat [40], VDI 2067 [41]. 4. Case study The three introduced tools were tested using a Case Study of an energy-optimized office building, using BIM (Building Information Modelling) [42]. The building model consists of a basement, and six storeys, it is of quadratic layout with side length of 24 m (Fig. 3). The office building is free standing, the primary structure in reinforced concrete, consisting of interior core containing staircase, elevator, and load bearing façade elements, with the slabs spanned in between. The façade is composed of vertical window stripes. The energy supply is carried out via geothermal energy and heat pump

(Table 2). The energy concept was developed for which an energy certificate was calculated using Archiphysik, thermal simulation using TAS, and light simulation using Dialux (Fig. 4). The assessed CC (construction costs) included cost calculation of: construction (structure) (CS), engineering e HVAC (CE) and CF (finishing elements). In order to enable comparability, the same parameters were used for all tools in the test (Table 3), the costs were calculated as NET values (excl. tax), related to the m2 GFA, according to formula (2):

LCC ¼ CC þ FC CC ¼ CS þ CE þ CF FC ¼ OPðECþMSCÞ þIC

(2)

4.1. Results Despite of the unification of the parameters and considered cost groups, the results differ strongly (Fig. 5 and Fig. 6). After inserting the same basic data and information in the tools, the construction costs diverge by max. 7%, however the following costs up to 38%.

Fig. 3. Case: regular floor.

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Fig. 4. U-value parameters and settings for energy certificate.

The comparison of LCC calculated by the three tools is hardly possible due to the different focus of each tool, different standard that the tool uses, and different planning stage for which the tool was conceptualised. DGNB/BNB indicator 16 for the pre-design; LEKOS for early design and LEGEP for the stage where the design is finished. Further on, only LEGEP has sufficiently extensive database, whereas the other two tools offer very few data, own data has to be inserted or bought. The Case Study is coherent with the benchmarks for the construction costs for office buildings as well as with the costs of realized energy efficient buildings. The calculated construction costs (structure, engineering, finishing) per m2 GFA range from 1,066 V/m2 GFA (LEKOS) till 1,164 V/m2 GFA (LEGEP) which comply with the referential values ranging from 970 to 1,260 V/m2 from BKI database [43], as well as with the realized construction costs of

Table 2 Case study data: building dimensions, energy demand. Site area Building dimensions width/length GFA NFA Useful area Window area Façade area Storey height Building height Building volume Reinforced concrete mass Heating energy demand/GFA Cooling energy eemand/GFA Light 8 W/m2

3,185 m2 24 m 4,212.46 m2 3,687 m2 2,119 m2 727 m2 2,352 m2 4.0 m 24 m 16,128 m3 947 m3 16.93 kWh/m2a 46.37 kWh/m2a 26 kWh/m2a

e.g. BOB-building [44] (low energy standard) which sum up to 1,070 V/m2 GFA. The variation of the discounting rate, price increase or energyprice increase represents the highest uncertainty, where even the small changes have a large impact on the final result. The whole simulation is controllable through these factors. The following graph (Fig. 7) displays the difference for the variation of the discounting rate of 0%, 3%, 5% und 5.5% using LEKOS software. With time horizon of 15 years, the initial investment (construction costs) still has the greatest percentage of the total costs. In short term view approach, life cycle costs loose on weight, where as reduction of initial investment stands in focus, opposing the interests of sustainability such as longevity. 4.2. Discussion of results The comparative study detected large differences in the results generated by the different tools, despite using the same entrance parameters. It can be concluded, that there is no “silver bullet” tool for LCC analysis, but the most suitable tool or method according to the project- or investor-specific needs has to be assessed. In the following section, three different scenarios for determining of WHO should carry out the life cycle costing used as a

Table 3 Definition of parameters for LCC. LCC Parameter

Value

Time horizon Discounting rate General price increase Energy price increase

50 yrs 5.5% 2% 4%

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Fig. 5. Comparison of construction costs (structure (CS), engineering (CE), finishing (CF)) assessed through three software tools.

Fig. 6. Comparison of the life cycle costs (CC þ FC) assessed through three software tools.

decision making support in early planning stages will be introduced. The investor-perspective is used, in the procurement stage (architectural competition). In Scenario 1 the investor (organization) calculates the LCC of the competition contributions. This scenario is built up on two preconditions: the investor-organization employs own suitable LCC-tool, and a well-organized and maintained life cycle costs database (for which financial, temporal and personal resources must be provided). The data-base should be built upon the knowledge and experience of investor-organization, employing the investmentand following-cost data of new projects as well as objects in use. This implies that the investor is not only developer, but also a

manager of certain stock (trade developer). In that case, the employment of LEKOS would be the advisable, since the investor already owns a good database. For the compilation of the LCCanalysis for the contribution-projects a significant time-effort on the investor-side is necessary. In Scenario 2 an external consultant is contracted with the calculation of the LCC of the contributions. This scenario fits to all of the investors who do not have own life cycle data pool (profit developer). In parallel, it can be started with building up of own life cycle cost data-base. The external consultant can be contracted project-wise until the knowledge within the company is built up. Advantages are that no own investment for the software, new technology or training, or time-effort for LCC analysis must be undertaken; the external specialist has access to large amount of data and know-how. Disadvantageous is a certain level of dependency to the consultant, especially related to the data protection. In the long run, it is less likely to build up own in-house knowhow. In Scenario 3 the partaking planners calculate the LCC in the course of the architectural competition. This arises following dilemma: should investor prescribe a unique tool or methodology; or can the tool-choice be left to the planner? If the competition participants are left with the choice of LCC tool, the parameters have to be pre-set by the investor (life duration, discounting rate etc.). However, the tool-test has shown that despite the pre-set parameters the results largely vary depending on the used tool, therefore this approach cannot be considered as accurate. Bounding all of the competitors to purchase and use one single tool is a less likely scenario in the case of open, public competitions. We recommend for this scenario utilization of a simple method, which allows comparison of projects, less than the actual accurate cost-prediction, for which e.g. the DGNB/BNB indicator 16 methodology is suitable. A simple Excel tool can be compiled and adapted according to the specific project focus and needs of investor, such as change of lifetime duration, discounting rate, or the ratios of the following, irregular costs. Due to the simple handling, the competitioncontributions can be proofed and compared with little effort. For all three scenarios building up of own life cycle cost database is advisable. In case of a trade developer (investor owns and manages the building) it is easier to create and maintain the database, in the case of profit developer, the data base could be created in joint venture with a network of facility management companies

Fig. 7. Variation of discounting rate parameter.

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Fig. 8. Comparison of LCC analysis assessed by adapted DGNB/BNB indicator 16 of real-life projects OPTI and STANDARD with the case.

in order to create a common knowledge and increase competitiveness on the market. Here each of the network-stakeholder would provide own data: the developers the data on construction costs, facility manager on the following costs. 4.3. Scenario 3 - verification In order to test the feasibility of LCC analysis in the earliest design stages (pre-design) Scenario 3 has been carried out using the adapted methodology of DGNB/BNB indicator 16 in a real-life architectural competition. For this purpose, a comparative LCC study of the competition-contribution project OPTI (energy-optimised office building) was compared to the standard office building STANDARD. Both projects were modelled upon data from extensive planner's database, where executed projects are documented in terms of construction and following costs, energy consumption, technology and similar. The available design information at this very early planning stage is still at conceptual level, therefore in very low resolution. Construction and HVAC systems are comprised of so called first level elements; the cost calculation is carried out using key figures in top down approach (V/m2 of GFA); as defined by the DIN or € ONORM standard; which define cost assessment procedure according to the planning stage. The largest difficulty at the early planning stage (pre-design) is availability of the energy performance data of the project, only in seldom cases a thermal simulation is carried out at this stage already. In this particular case it was advantageous that the project was designed by an integrated planning team, including an architect, HVAC engineering and energy consultant, which enabled an early design of an energy supply and HVAC concept, and prediction of energy consumption based on the design. To verify the results, the two real-life projects were also compared to the Case Study, which was formerly calculated by the DGNB/BNB indicator 16 in the course of tool-comparison. In order to be able to compare the OPTI and STANDARD office buildings with the Case all of the data (CC, FC, LCC, EC) is broken down to V/m2 GFA (for CC, FC, LCC) or energy consumption in kWh/m2 GFA. The yearly following costs were calculated based only including energy consumption (waste, water and cleaning excluded) and

MSC(maintenance and service ) as yearly percentage of construction costs, for which planner's database was used.

LCC ¼ CCðCSþCEþCFÞ þFCðECþMSCÞ

(3)

whereby. Yearly MSC(CC) ¼ x% * CC Yearly MSC(CE) ¼ y% * CE Yearly MSC(FC) ¼ z% * FC The LCC analysis for the Case is using the BKI [42] database for the initial investment, energy certificate for assessment of energy costs, and DGNB/BNB indicator 16 [35] referential values (percentages) for the calculation of MSC. OPTI and STANDARD are using, based on the architectural and energy concept, planner's data base for key figures for assessment of construction costs and following cost-ratios, and energy consumption. The analysis shows, that the case has the lowest CC as well as the LCC (Table 4); differently to the expectations that this should be OPTI through lowest energy consumption. This result is partially due to the fact that the CC for the Case, based on the BKI referential values are probably too low for the building of such energy

Table 4 LCC-Model for OPTI; STANDARD and Case.

CC ¼ CS þ CE þ CF (V) CS (V) CE (HVAC) (V) CF (V) Energy consumption (kWh/m2) Energy price (V/kWh) (Mix 30% gas þ 70% electricity) Renewal floors/years Renewal façade/years Renewal HVAC/years Maintenance cost/HVAC yearly Maintenance façade/yearly Maintenance floors/yearly

OPTI

STANDARD

CASE

1,200 507 420 273 80 0.09

1,150 604 345 201 120 0.09

1,147 485 401 261 90 0.11

15 35 25 0.8% 1.3% 0.6%

7 30 20 1.2% 1.6% 1.2%

15 30 25 1.3% 0.7% 0.7%

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I. Kovacic, V. Zoller / Energy xxx (2015) 1e11

standard; since the CC have large impact on the MSC, which are obtained as yearly percentage of the respective CC in this methodology (Fig. 8). Further on, it is obvious, that with rising level of energy efficiency, the portion of energy consumption in the following costs is decreasing, and the quality of construction (long life-duration and maintenance-free) expressed in irregular costs starts playing important role for the optimization of LCC (Table 5). In general, the applied methodology offers quick insight and transparency in how the costs were calculated and enables the comparison of the positions. 5. Conclusion The application of the LCC analysis as decision support for investors in the early stages of building design is still facing numerous difficulties, such as the availability of the reliable data in the first place, diverging life cycle costs standards and a mismatch between the design information availability and design stage significance; as was demonstrated through test of the LCC tools. It was shown, that the tested tools are only partially suitable as “out of the box” solutions, and need customized adaptation. As the most suitable tool for the Austrian market the ABK LEKOS was identified, however facing the problem of data-lack e the database contains only the data for the office building of middle standard, which is not suitable for other typologies such as schools, housing etc. LEGEP tool is less suitable for assessment in the early design stages, due to the high resolution of required input information, which is not available at the beginning of design. Due to the information richness, this software enables assessment, comparison of variants, or of different building elements for the life cycle performance. The very comprehensive database enables the modelling of various building typologies; however at the latter planning stages, where exact information on building design is available. The DGNB/BNB indicator 16 is not suitable for the planning of investments or financing, since the considered cost groups cover only certain aspects of the whole cost spectrum. It can be used for comparative study of different projects, or even of element variants such as façades. Further on, we proposed an adapted form of DGNB/ BNB indicator 16 for the LCC analysis in the earliest design stages serving as comparative tool in the course of architectural competition. In order to test the usability of LCC analysis as decision-making support for investors in the pre-design stage, three different scenarios were developed. In the first scenario the investor calculates the LCC and proofs the project-contributions in terms of LCC performance, which is cost and time intensive, own knowledge base in the company is predisposition. In the second scenario a consultant is hired for this process, which is costly and does not contribute to building up of knowledge within investor organisation. In the third scenario, the LCC analysis is carried out by the planners partaking in the architectural competition.

Table 5 Results of LCC analysis for OPTI; STANDARD and Case.

Investment CC/m2 GFA (V) Operational costs OC/m2 GFA Maintenance and renewal costs MSC þ IC/m2 GFA (V) LCC/m2 GFA % of EC in FC % of CC in LCC

OPTI

STANDARD

CASE

1,200 490 1,007

1,150 662 1,066

1,147 535 927

2,697 33% 44%

2,879 38% 40%

2,609 37% 44%

The third scenario was executed in order to verify the feasibility of such procedure e an adapted DGNB/BNB excel tool served as basis for the LCC analysis in the course of real architectural competition, with which three projects (contribution - OPTI, STANDARD and Case) were calculated and compared. The study shows, that through energy-optimized construction, 33% of the total energy consumption was saved, and the life cycle costs reduced by 7% (in the case of OPTI compared to STANDARD). However, a reduction of energy-consumption by 25% saves 10% of the LCC (Case compared to STANDARD). With the increasing energy-efficiency level, the investment costs are also increasing. This is especially true for the cost group Construction Engineering (HVAC), as well as the maintenance costs of the high-tech façade incorporating ventilation, the heating and cooling components, which contributes to the increase of the yearly costs. Thereby finding the optimum between the energy-savings and economic life-cycle costs and benefits is necessary, in order to prevent the over-investment as defined by Ellingham and Fawcett [17]. Next to the energy consumption, the maintenance and renewal costs of construction and HVAC elements play important role; for assessment of which more reliable data is necessary. It can be concluded that more research is necessary in order to gain knowledge on the exact exceeding point of the following costs over construction costs, as well as on the impact of integrated design on the life cycle performance of the building. For gaining more empirical data and knowledge on the cost performance of buildings throughout the operation, the comparability of LCC studies has to be ensured through the application of the same cost-standards, boundary conditions and parameters such as discounting rate, inflation rate and time horizon. The conducted research of LCC analysis in the early design stages has limitations, in particular the local context of German speaking regional construction and related normative, as well as of the used data (construction, HVAC and energy prices). Further on, if using the LCC as a tool for sustainability assessment, due to the large impact of highly uncertain factors (discounting rate, price increase, energy-price increase) evaluation of additional aspects such as social and ecologic impacts has to be assessed, for example using combined LCC and LCA approach [45,46]. €ki at al pledge for economical and ecological life cycle Ristima analysis as decision support for real estate investors, and towards paradigm change of building life-cycle as key performance indicator [47,48]. Seen in this light, more incentives for increased weighting of life cycle costs and emission in decision making process, and reliable decision-support tools should be developed for investors.

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Please cite this article in press as: Kovacic I, Zoller V, Building life cycle optimization tools for early design phases, Energy (2015), http:// dx.doi.org/10.1016/j.energy.2015.03.027