2d3dreportrevisionsubbyworkbook

Blog

Embedding Life Cycle Costing in 5D BIM

Embedding Life Cycle Costing in 5D BIM

For this blog post we have a guest post from Dr Dermot Kehily from Dublin Institute of Technology. Dermot recently had a paper published in International Journal of Information Technology in Construction (ITCon) regarding research on LCC and BIM, which was a synopsis of his PhD research regarding utilizing 5D BIM (CostX®) for Life Cycle Costing. He has summarised the key findings of the paper below.

1. BIM AND LIFE CYCLE COSTING
Life Cycle Costing (LCC) is an area in Quantity Surveying (QS) practice that is concerned with the calculation of both construction CAPital Expenditure (CAPex) and OPerational Expenditure (OPex). Despite the significant amount of research in LCC in the last fifteen to twenty years, it has not been extensively implemented into QS practice. QSs require a means to carryout LCC effectively in line with the relevant standards and guidelines.

Building Information Modelling (BIM) offers capabilities that can aid QSs increase efficiencies in their work practices. One of the primary benefits of BIM for QSs is that it can automate Quantity Take-Off (QTO) and free up time to concentrate on activities that would add further value for their clients. While LCC is identified as a value enhancing service, there has been limited research on how BIM could be leveraged to increase efficiency in facilitating this service.

In the 5D BIM process, practitioners can move from spending time on generating quantity and cost information, to validating the quantities and costs contained within their CAPex estimates. To carry out effective 5D BIM, QTO must be generated from the BIM to suit QS requirements and measurements rules. This process is defined as ‘model mapping’, where the objects in the model are attributed to a QS Work Breakdown Structure (WBS), so that when the quantities are extracted they are aligned to that code.
BIM authoring tools do not currently have the probabilistic capabilities to accommodate the variable conditions for LCC analysis. A more flexible structure than BIM can provide is needed for the probabilistic nature of LCC calculations and the many variables necessary for ‘what if’ analysis.

2. EMBEDDING LCC IN 5D BIM
In this research, a LCC calculation structure is incorporated into a 5D BIM platform. The research adopted CostX® 5D BIM software by Exactal. CostX® was selected because it has a ‘workbook’ that is similar to the functionality and capabilities of a spreadsheet, giving the user an opportunity to add new columns, rows and functions that can link calculations between them. Furthermore, CostX®’s spreadsheet functionality can be utilised to replicate the LCC calculation structures proposed in LCC international methodologies and standards, which are based on spreadsheets.

Fig. 1 represents the summary page and the total line items for the three relevant sub-sheet calculations in the LCC calculation methodology proposed in this research. These three sub-sheets form the basis for any LCC calculations in an LCC estimate. In the example presented in Fig. 1, the summary structure is broken down per the WBS recommended in ISO 15686-5 for ‘Buildings and constructed assets; Service-life planning; Part 5: Life-cycle costing’. Clicking on the line of the relevant element (WBS) in the summary, the user is able to access the applicable sub-sheet and LCC calculations to build up LCC costs within that element.

CostX summary sheet

FIG. 1: Summary Sheet

The first sub-sheet (Fig. 2) deals with the calculation of full replacement cost items in an LCC estimate. User defined LCC columns are added to the CostX® workbook (in this sub-sheet) to enable LCC calculations for major replacement items. The LCC cash flows throughout the analysis period and the total LCC costs (real, escalated and present value) are automatically calculated and populated from the LCC data requirements outlined in the calc sheet of the workbook (see full paper for details) and the replacement period and uplift factor entered in the LCC user defined columns in Fig. 2. The majority of cost plan items will also need an uplift factor, for preparation, demolition and making good to receive new work, over and above the basic installation cost. To enable the LCC calculations expounded in Fig. 2, ‘IF’ scenario formulae are embedded in each of the yearly cash flow cells for every line item. These formulae are similar to MS Excel functions and automate the calculation of cash flows by utilising ‘IF’ functions deriving data from the ‘Replace Period’ (column J), the ‘Uplift Factor’ (column K) and the data requirements. If any of these variables change the calculations, resultant cash flows and total LCCs (real, escalated and present value) will be updated. In this example, a ‘Present Value’ cash flow is generated for replacing the ‘910 x 2110 Internal door’ every 6 years within the 30 year analysis period, input in the data requirements (i.e. year 6,12,18,24,30). The ‘IF’ functions dictate that any year that is not a multiple of the ‘Replace Period’ will have a value of ‘0’. Cash flows for ‘Real’ and ‘Escalated’ costs are calculated in the same manner (albeit with different formulae), but are not included in this screenshot as the expanded scope would limit the clarity of the illustration. As demonstrated in Fig. 1, these LCC totals (columns L, M and N) and the accumulated cash flows carry forward to the relevant element on the summary sheet. The same sub-sheet can be used to represent the relevant ‘major maintenance and replacement costs’ for every applicable elemental category in the LCC estimate.

LCC Calculation Sub-Sheet

FIG. 2: LCC Calculation Sub-Sheet [1]
*Refer to full paper for details of subsheet 2 and 3.

3. FINDINGS
BIM makes it possible for consultants to expand the scope of their services by freeing up time in the laborious QTO process. Despite the benefits of LCC, it is a service that is not widely practiced by QSs due to a number of barriers that impede its implementation. While consultants are developing capabilities in BIM for QTO and CAPex estimating, there is an overall lack of enthusiasm utilising BIM for LCC. This is not a product of QS’s lack of experience with BIM but rather their lack of knowledge of LCC and how BIM could be utilised to increase efficiency in providing this service.

Feedback from the participants in this study indicated that leveraging 5D BIM and incorporating a LCC calculation structure automates LCC, thereby making it easier and significantly quicker to carry it out. Participants noted that these calculations populate cash flows and cumulative LCC totals within a standard structure. Rooting the LCC calculations in a spreadsheet format was expressed as a benefit, because it is the medium in which QSs are most familiar with and thus, expedites their learning curve.

The most prevalent theme that emerged from feedback from the participants is that this is a unique process enabled by an integrated 5D BIM based LCC technology (CostX® embedded with LCC calcs). Ultimately, CAPex and LCC reports can be generated from the same integrated system. The benefits of an integrated process give users the tools to interrogate the effect of different variables in both their CAPex and their OPex LCC estimates. Participants note that this advantage maintains transparency and links the workflows across the 5D BIM LCC process, providing efficiencies in quicker calculations and presentation.

The findings indicated that this process would make it easier and more likely that QSs would provide LCC services for their clients. All participants noted that they would use this system, if it were available to them. This study indicated that the direct benefits to the QS are:

  1. It can aid them in the calculation of tenders with an FM element such as PFIs;
  2. It can save outsourcing LCC to external consultants;
  3. CAPex and LCC can be incorporated in the same process;
  4. QSs can get more from their existing software without the expense of buying additional BIM LCC software.
  5. Rooting the LCC calculations in a spreadsheet; it is the medium in which QSs are most familiar with and thus, expedites their learning curve and facilitates trust in the process.

A number of participants commented on improving the integration between the BIM output and the LCC calculation structure. These recommendations propose that LCC data could be contained in the object properties of the authored model, which could then be utilised in the LCC calculations. This would essentially entail extracting LCC information from the model and linking it directly to the calculations in the LCC workbook. Existing practice is that this information comes from the QS’s database, but if, as a number of participants recommended, this information was included in the object properties of the design model, it would make it easier for QSs to access this information and provide further integration and automation in the 5D BIM LCC workflow. This could particularly have an effect on the access to LCC information barrier and speed up the production of LCC estimates by linking to data in the authored model.

To read the full paper, please click here.