Civil Engineering Reference
In-Depth Information
Chapter 13
Uncertainty and Risk Management
13.1
Probabilistic Versus Deterministic Simulation
The primary purpose for performing an energy modeling for a building and its
systems is to predict the future energy consumption of the building. To perform an
energy modeling simulation, in addition to the need for keying in all the physical
dimensions, orientation and constructing elements characteristics of the building, it
is required to enter almost all the building constructing elements and their thermal
characteristics, and all the utilized systems and their required enabling power for
operation and level of effi ciencies, into the model as input. Available commercial
simulation software uses its underlying mathematical structure and executes proper
calculations with this information to provide a single estimated output which repre-
sents the total building yearly energy consumption level.
The simulation software therefore performs a deterministic procedure, assum-
ing, e.g., all the material that actually will be used in construction of the building has
the exact heating characteristics, and all the utilized systems in the building hold the
exact energy effi ciency levels that has been assigned to them by the modeler. To
some extent these are legitimate assumptions, since to the best of their efforts, the
architect and engineers supervise the purchasing and installations of all the building
elements and systems according to the specifi ed specifi cations in building design
construction document. But is that enough?
In reality, when the architect through the building design specifi cations e.g. spec-
ifi es a certain type of stone that has a specifi c heating characteristics (
U
-value) to be
used as one of the building façade constructing elements, even though the suppliers
provide material with the exact heating characteristic as it was indicated in design
specifi cations, this does not mean that every single face stone installed in the project
has the exact same characteristics. Actually it might even be correct to say that
almost none of the used surface stones have the same exact characteristics as it was
specifi ed. This is due to lack of complete accuracy in testing condition and testing
apparatus utilized by the different manufacturers during the production of surface
