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|One of the three types of models
to calculate reinvestment
rates for maintenance
and renewal costs (ie., Keep-up
Costs) at different stages in a
These methods use mathematical expressions made up of quantifiable variables. They are based on the assumption that annual maintenance and renewal funding requirements can be estimated with a mathematical equation. The formulas are typically algebraic, regression analysis or simulation based on historical data. The expressions range from simple single-variable equations to very complex. The figure alongside contains an example of the mathematical expression from the NACUBO model.
Whereas the lifecycle models require data on the benchmarked useful service life of the sub-systems within a building, the mathematical models can either exclude this parameter or include additional parameters
Some of the additional parameters used in the mathematical expressions are: location/climate zone, age, size, type, construction costs for different sub-systems, facility operating budgets and condition data.
Some examples of mathematical models include:
EvaluationThe mathematical models are typically the most defensible of the three types of desktop assessments and the assumptions in the models can be validated through a subsequent condition assessment at Level II or III.
These methods are typically more data-intensive than the life cycle models and some of the data can be difficult to obtain. Several assumptions may therefore need to be made based on condition assessments performed on buildings with similar attributes.
Fig. An example of the mathematical expression from the NACUBO model.
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