This process continues through three stages of design as illustrated in Figure 0.2. and at each stage an Environmental Impact Analysis may be carried out. This is dealt with later.
By using this approach, the design team can create and audit trail of all decisions that have been taken and on what evidence the decisions are based. This approach helps focus all the stakeholders on WLC and can additionally help with other matters such as CDM regulations compliance, Local Authority Best Value directives etc.
The log book is used to set up the Project and to create the building model and the client brief is reported. The LCCP model is one of the tools that support the decision-making. The decision framework is illustrated in greater detail in Figure 0.3.
OPEN PROJECT
CALCULATE ENERGY
COSTS CREATE
BUILDING MODEL
CALCULATE FINANCIAL
COSTS CALCULATE
FM COSTS CALCULATE
CAPITAL COSTS
CALCULATE MAINTENANCE
COSTS CALCULATE
RESIDUAL COSTS
ASSESS COSTS CALCULATE SERVICE LIFE
Element Life Building
Model
Log Book Brief
Project
@RISK Report
Element Cost RECORD
DECISION FILL OUT CLIENT BRIEF
Analysis Note
Figure 0.3 The decision framework
WLC model components
A critical element of any cost model is the cost breakdown. Following consultation with industry a tailor made cost structure was developed with the main objective of reflecting a wide range of estimating practices and being applicable both to capital and lifetime costs. The cost structure was also developed to allow the user sufficiently flexible to establish a unique structure for a particular project, but within a broader generic framework. It was further recognised that the user will not necessarily wish to drill down to a detailed level to minimise uncertainties for all components (Figure 0.4).
Figure 0.4 Tailor made cost structure
Screening using a risk register or a system such as the 80:20 rule, which acknowledges that 80% of the cost is associated with 20% of the building components (Figure 0.4) will identify where the effort can be maximised in terms of it impact on the lifetime cost.
In a study of the tender costs for a PFI hospital, the 80:20-rule appeared to be closer to 70:30, as shown in Figure 0.5. Nevertheless, the principle that a majority of the cost is attributed to a minority of expensive components applies. The ratio varied for different systems, e.g. mechanical, electrical, but the principle was consistent. It should also be noted that the analysis used to provide
CLIENT BRIEF
CONCEPT DESIGN
DETAILED DESIGN
the relationships in Figure 0.4 did not break down the systems into all of the individual components.
The greater the level of breakdown, i.e. the greater the number of components, the closer the ratio is likely to move towards 80:20.
LCC
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100%
% of items
% of cost Mechanical
Electrical Other elements All elements
Figure 0.5 The relationship between percentage cost and percentage of component for a PFI hospital in the UK
Dealing with uncertainties
It is recognised that in any prediction there will be uncertainties and the process that has been developed provides a means for dealing with these uncertainties using a probabilistic approach.
Input data for both performance (service life) and costs are input in the form of ranges of values (maximum, most likely and minimum) or statistical distributions. The output costs are then associated with a defined level of probability, enabling the user to make rational and transparent decision about changes in relation to financial risk.
Software applications
The Whole Life model comprises three decision tools which are linked through the log-book.
• The logbook
• A deterioration model, including the SL database
• The LCCP calculator
• An environmental screener
The above tools may be applied individually or may be used in combination to achieve the most cost-effective life cycle design which meets definable environmental and societal criteria. The general approach to the application of the model components is as follows.
The process begins by opening the logbook (Figure 0.6). Page 0 of logbook is used to record the general project information.
Figure 0.6 Logbook, Page 0 – Client Brief (left) and Logbook Page 1 – Design and Construction (right
Page 1 of logbook is used to record decisions that are made during the design and construction process, although for the purpose of the case studies it is likely that only design decision will be included.
On page 1, the logbook has a link to the LCCP model which must be opened to enable the cost tree to be established (Figure 0.7). The costs may be broken down to various levels, depending on the information available to the user and the requirement of the particular analysis.
The process begins at the Client Brief stage. Information here is at high level, e.g. floor area for an office building, number of beds for a hospital, number of pupils for a school, and the high level cost is based on a unit rate, e.g. €/m2, €/bed, €/pupil respectively. FM costs may be presented as a % of capital cost or on a unit basis, e.g. €/m2/yr. There will be a number of uncertainties relating to the capital costs and the operational and FM costs. Run a simulation at concept level to identify where the uncertainties are greatest and hence where to focus more detailed analysis.
At concept level it is only necessary to deal with the following;
Capital cost; Operational costs; Maintenance (PPM and reactive); Life cycle replacements; Costs at the end of the study period.
The Client Brief tab opens a series of pages that request information for the costs shown in the cost tree. All of the information is input either as a range of values [presented as minimum, maximum and most likely] or as a distribution if more rigorous data are available. In addition, for each input the type of distribution may be selected or, if adequate data are available, the best fit distribution may be determined (Figure 0.8)
Figure 0.7 Development of the cost tree in the LCCP model
Explicitly represent uncertainty using a suitable probability
distribution
Figure 0.8 Probability distributions available within the @Risk package
If no data are available then a triangular distribution is used as the default. If there is no uncertainty about the input data then the max, min and most likely values will be the same. A range of outputs are available as selected by the user but at the strategic level two outputs are most significant as follows (Figure 0.9)
• A probability curve for the life cycle cost – this provides the user with an assessment of the likelihood of the costs exceeding particular values and provides necessary information for the management of financial risk
• A sensitivity analysis – this provides the user with information on those factors to which the output is most sensitive (i.e. those factors that make the biggest difference to the cost if changed).
These outputs, together with the assumptions and values used in deriving them, are recorded in the logbook. This must be done by allocating a file name to the outputs, storing them in the project file and recording the file details in the logbook. If necessary the simulation may be rerun with revised data, taking account of the results from the sensitivity analysis, until the level of uncertainty is reduced to an acceptable level. Information provided at this level is intended to provide a basis for strategic decisions.
Regression Sensitivity for Total Cost (¬)/F28
0.737 0.559 0.265 0.244 0.163 0.102 0.076 0.051
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Earthworks / Distribution/J11 Labour / Distribution/J18 Concrete/L16 Planning / Distribution/J8 Plant hire/L21 Steel/L14 Road surfacing/L23 Administration/L25
Std b Coefficients
Record in logbook Record in
logbook
Normal(1000, 100) vs Normal(1000, 200)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.38 0.685 0.99 1.295 1.6
Values in Thousands
Figure 0.9 Probabilistic inputs and to obtain a cost probability curve and a sensitivity analysis Having decided to proceed with the project the user enters the design stage and expands the cost tree to include a number of elements of the structure. Initially these should be at system level and include, for example, the superstructure, cladding, services and finishes. At this stage a simple deterioration model, based on ISO adjustments to reference SL values, should be applied. The user constructs the cost tree to be consistent with the particular project and components under consideration. For example, when considering different cladding types, the cost of heating the building may be important to include in the model. For each component, the deterioration model includes service life values (expressed as min, max and most likely) and with no other available data, these values may be used as a default. The simulation is then rerun and the results are recorded in the logbook. Once again, the principal outputs will be the cost probability curve and the sensitivity analysis. At this stage it may also be appropriate to produce a variety of outputs, each with their own sensitivity analyses. For example, it may be advantageous to review the capital costs and the operational costs separately as they may be sensitive to different factors.
Having identified the items to which the costs are most sensitive, a more detailed analysis may be undertaken using the deterioration model. This will involve providing more rigorous data to reduce the uncertainties for the selected system, conducting a scenario analysis looking at a number of options and justifying the design decision based on the LCCP results. The deterioration model provides probabilistic outputs that may be copied into the LCCP model for incorporation in the larger simulation as shown in Figure 0.10.
Figure 0.10 Output from the deterioration model into the LCCP model
In practice there may be several iterations, as shown in Figure 0.11, in order to reduce all of the uncertainties to an acceptable level.
Regression Sensitivity for Total Cost (¬)/F28 0.737 0.559 0.265 0.244 0.163 0.102 0.076 0.051
-1 -0.8-0.6-0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Earthworks / Distribution/J11 Labour / Distribution/J18 Concrete/L16 Planning / Distribution/J8 Plant hire/L21 Steel/L14 Road surfacing/L23 Administration/L25
Std b Coefficients
Simulation
Sensitivity analysis
Deterioration modelling
Record in logbook Record in
logbook
Normal(1000, 100) vs Normal(1000, 200)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.38 0.685 0.99 1.295 1.6
Values in Thousands
Figure 0.11 Iterations of simulations and sensitivity analysis to reduce uncertainties
When the simulations have been completed for a particular scenario and the probability curve has been derived, the user may use this to select an estimated cost at which the financial level of financial risk is acceptable, as shown in Figure 0.12.
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
290 300 310 320 330
Cost in Thousands
Cumulative probability
Contingency
Margin
From 100% - 80% risks easily removed with good management From 80% to 50% risks removed with much hard work, good management and some luck From 50% to 20% risks removed with very hard work, good management and lots of luck
Select acceptable level of risk
Figure 0.12 Selecting an acceptable level of financial risk
The environmental screener is accessible directly from the logbook and may be used in two ways.
This uses multi criteria decision analysis. At the simplest level it may be used to assess each of the scenarios investigated by comparison with benchmark data. Scenarios which fail to meet minimum acceptable levels may then be either rejected or modified to meet the necessary criteria. This approach is only applicable, however, when there are benchmark levels available.
The second method of application is as a comparator to aid selection when various scenarios have been considered. In this case the screener is used to assess each of the options and the environmental score is considered against the life cycle cost, as shown in Figure 0.13. This approach enables the cost of improving the environmental score to be assessed. The environmental screener may be used at any stage within the design process
0 20 40 60 80 100
30 35 40 45
Cost at acceptable risk
ENV Score
Project: NN
Phase: Client Brief Yes/No
Concept Design Yes/No National or EU regulations:
Detailed Design Yes/No Energy Performance of Buildings:
Completed by: nn
Date: dd.mm.yyyy
Design Life (years) Phase Weights Environmental Weights Parameters WeightsAssessment Points
50 Principal Impacts Impact ParameterYes = 1
Period of Analysis (years) (%) (%) (%) Partly = 0.5
50 No = 0
Environment Construction 10.2 Energy 33 Energy management 50 0.0
Renewable energy 50 1.0 1.7
Sum 100 1.7
Materials 33 CFC and HCFC 50 0.5 0.8
Env. Declaration or label 0 0.0
PVC 25 0.5 0.4
Recycled or reused materials 0 0.0
Renewable resources 25 1.0 0.8
Sum 100 2.1
Waste 34 Waste management 50 0.0
Waste reduction 50 0.0
Sum 100 0.0
Scoring construction 100 3.8
Operating & Maintenance 84.8 Energy 50 Low energy windows 17 0.0
Monitoring and control 17 0.0
Solar cells 17 0.0
Solar heating system 17 0.0
Ventilation and cooling 17 0.0
Water-cooling 17 0.0
Sum 100 0.0
Materials 10 Env. Sound cleaning 33 0.0
Env. Sound maintenance 33 0.0
Replacement frequency 33 0.0
Sum 100 0.0
Waste 20 Composting 50 0.0
Waste sorting 50 0.0
Sum 100 0.0
Water 20 Collection of rainwater 50 0.0
Water conservation installation 50 0.0
Sum 100 0.0
Scoring Operating & Maintenance 100 0.0
Disposal & Residual Value 5.0 Disposal 100 Design - sorting and reuse 33 0.0
Materials - sorting and reuse 33 0.0
Residual value environmental 33 0.0
Sum 100 0.0
Scoring Disposal & Residual Value 100 0.0
Scoring Environment Max 100.0 100.0
Scoring Environment 100.0 3.8
Rating 0.04
Occupation Operating & Maintenance 100.0Air quality and temp. 50 Adjustable temperature 33 0.0
Harmful fumes 33 0.0
Ventilation 33 0.0
Sum 100 0.0
Daylight and lighting 25 Daylight 50 0.0
Sunlight protection 50 0.0
Sum 100 0.0
Indoor noise 25 Design 50 0.0
Materials and components 50 0.0
Sum 100 0.0
Scoring Occupation 100 0.0
Scoring Occupation Max 100.0 100.0
Scoring Occupation 100.0 0.0
Rating 0.00
Mobility Operating & Maintenance 100.0Transport 100 Public transport 20 0.0
Usage of public tr.; staff 20 0.0
Transport distance; staff 20 0.0
Environmental Impact Assessment needed?
Effective Jan 2006 for new and refurbishment over 1,000 m2 floor
Record in logbook Record in
logbook
Figure 0.13 Use of the environmental screener to compare various options
At each stage of the analysis and for each of the scenarios, the assumptions made and the decisions taken are recorded in the logbook. Hence, at the end of the design stage, there is a comprehensive record of the components and materials specified together with the assumptions about both the cost and performance.
The logbook is then handed over to the contractor and any changes that are made during the construction process and the assumptions about the implications of these changes are also recorded.
Hence, at completion of construction there is a record of components and materials actually used (with a record of all changes from the original design and the implications in relation to the long term performance and life cycle costs.
The logbook then becomes the responsibility of the building owner/occupier to enable the actual life cycle cost and performance to be recorded. The information collected will then provide a means for the facility manager to monitor and manage the maintenance and replacement of components, and will also provide additional data for use in subsequent designs.
References
APPENDIX: Terms and Definitions of the Lifecon LMS
TERM DEFINITION Life cycle and life time
Life cycle The consecutive and inter-linked stages of a facility or structure, from the extraction or exploitation of natural resources to the final disposal of all materials as irretrievable wastes or dissipated energy.
Lifetime The time period from start of the use of a facility or structure until a defined point in time.
Design period A specified period of the life time, which is used in calculations as a specific time period.
Design life, or Design working life (EN 1990- 2002)
Assumed period for which a structure or part of it is to be used for its intended purpose with anticipated maintenance but without major repair being
necessary
Serviceability and service life
Serviceability Capacity of a structure to perform the service functions for which it is designed and used.
Service life (ENV1504-9:1996)
• target life
• characteristic life
• design life (or: design working life) (EN 1990- 2002)
• reference service life
The period in which the intended performance is achieved.
Required service life imposed by general rules, the client or the owner of the structure or its parts.
A time period, which the service life exceeds with a specified probability, usually with 95 % probability.
Assumed period for which a structure or part of it is to be used for its intended purpose with anticipated maintenance but without major repair being
necessary. Design life is calculated dividing the characteristic life with lifetime safety factor. Calculated design life has to exceed the target life.
Service life forecast for a structure under strictly specified environmental loads and conditions for use as a basis for estimating service life.
Residual service life
Time between moment of consideration and the forecast end of service life.
Service life design
Preparation of the brief and design for the structure and its parts to achieve the desired design life e.g., in order to control the usability of structures and facilitate maintenance and refurbishment.
Reference period
(EN 1990-2002)
Chosen period of time that is used as a basis for assessing statistically variable actions, and possibly for accidental actions.
Reliability and performance Reliability
(EN 1990-2002)
Ability of a structure or structural member to fulfil the specified requirements, including the design working life, for which it has been designed. Reliability is usually expressed in probabilistic terms.
NOTE: Reliability covers safety, serviceability and durability of a structure.
Reliability differentiation (EN 1990-2002)
Measures intended for socio-economic optimisation of the resources to be used to build construction works, taking into account all the expected consequences of failures and the cost of the construction works.
TERM DEFINITION Performance Measure to which the structure responses to a certain function.
Performance requirement or performance criterion
Qualitative and quantities levels of performance required for a critical property of structure.
Life time quality
The capability of the facility to fulfil all requirements of the owner, user and society over the specified design life (target life).
Failure
• durability failure
Loss of the ability of a structure or its parts to perform a specified function.
Exceeding the maximum degradation or falling below the minimum performance parameter.
Failure probability
The statistical probability of failure occurring.
Risk Multiplication of the probability of an event; e. g. failure or damage, with its consequences (e. g. cost, exposure to personal or environmental hazard, fatalities).
Obsolescence Loss of ability of an item to perform satisfactorily due to changes in human (functionality, safety, health, convenience), economic, cultural or ecological requirements.
Limit state (EN 1990-2002)
• serviceability limit state
• irreversible serviceability limit states
• reversible serviceability limit states
• ultimate limit state
States beyond which the structure no longer fulfils the relevant design criteria.
State which corresponds to conditions beyond specified service requirement(s) for a structure or structural member are no longer met.
Serviceability limit states where some consequences of actions exceeding the specified service requirements will remain when the actions are removed Serviceability limit states where no consequences of actions exceeding the specified service requirements will remain when the actions are removed State associated with collapse or with other similar forms of structural failure.
Serviceability criterion (EN 1990-2002)
Design criterion for a serviceability limit state.
Lifetime safety factor
Coefficient by which the characteristic life is divided to obtain the design life.
Factor method Modification of reference service life by factors to take into account of the specific in use conditions.
Attribute
• multiple attributes
A property of an object or its part, which will be used in optimisation and selective decision making between alternatives.
A set of attributes, which will be used in optimisation and selective decision making between alternatives.
Durability
Durability The capability of a structure to maintain minimum performance under the influence of actual environmental degradation loads.
Durability limit state
Minimum acceptable state of performance or maximum acceptable state of degradation.
TERM DEFINITION Durability
model
Mathematical model for calculating degradation, performance or service life of a structure.
Performance model
Mathematical model for showing performance with time.
Condition Level of critical properties of structure or its parts, determining its ability to perform.
Condition model
Mathematical model for placing an object, module, component or subcomponent on a specific condition class.
Deterioration The process of becoming impaired in quality or value.
Degradation Gradual decrease in performance of a material or structure.
Environ-mental load
Impact of environment onto structure, including weathering (temperature, temperature changes, moisture, moisture changes, solar effects etc.), chemical and biological factors.
Degradation load
Any of the groups of environmental loads, and mechanical loads.
Degradation mechanism
The sequence of chemical, physical or mechanical changes that lead to detrimental changes in one or more properties of building materials or structures when exposed to degradation loads.
Degradation model
Mathematical model showing degradation with time.
Management and maintenance Maintenance
(EN 1990-2002) Set of activities performed during the working life of the structure in order to enable it to fulfil the requirements for reliability
NOTE: Activities to restore the structure after an accidental or seismic event are normally outside the scope of maintenance.
Repair (EN 1990-2002)
Activities performed to preserve or restore the function of a structure that fall outside the definition of maintenance.
Restoration Actions to bring a structure to its original appearance or state.
Rehabilitation Modification and improvements to an existing structure to bring it up to an acceptable condition.
Renewal Demolition and rebuilding of an existing object.
M&R Maintenance, repair, restoration, refurbishment and renewal, or some of them.
Project Planning and execution of repair, restoration, rehabilitation or dismantling of a facility or some parts of it.
Life cycle cost Total cost of an asset throughout its life, including the costs of planning, design, acquisition, operations, maintenance and disposal, less any residual value.
Environmental Burden
Any change to the environment which permanently or temporarily, results in loss of natural resources or deterioration in the air, water or soil, or loss of biodiversity.
Environmental Impact
The consequences for human health, for the well-being of flora and fauna or for the future availability of natural resources. Attributable to the input and output streams of a system.
Integrated lifetime design of materials and structures
Producing descriptions for structures and their materials, fulfilling the specified requirements of human requirements (functionality, safety, health, convenience), monetary economy, ecology (economy of the nature),and culture , all over the life cycle of the structures. Integrated structural design is the synthesis of mechanical design, durability design, physical design and environmental design.