Civil Engineering Reference
In-Depth Information
Table 2 Construction-phase uncertainties
Construction
uncertainties
Classification
Characteristics
Scheduling uncertainty
Internal
Activities during the construction process are subject
to considerable uncertainty due to preexisting
conditions (Cattano et al.
2012
). For example,
resources may become unavailable or new
activities may have to be incorporated due to
changes in the refurbishment scope. In addition,
contractors might need to work around tenants who
are not fully evacuated; thus, all construction
activities need to be scheduled taking that into
account. All of these will affect the schedule and
time of completion of the project
Budget and financing
decisions
Availability of continuous funding and the duration
and availably of tax rebates and incentives to
support construction activities might change over
the duration of the project (Baden et al.
2006
). In
addition, unforeseen conditions in the existing
building may force stakeholders to reduce the
scope of the project when the cost to refurbish
exceeds the allocated budget, and additional
financing cannot be secured (Menassa
2011
)
Preexisting conditions
External
Unforeseen site conditions are among the largest
contributing factors of uncertainty during the
construction phase because it impacts both the
project schedule and allocated budget (Cattano
et al.
2012
). Hidden preexisting conditions might
cause budget overrun and construction delays
Material functional
characteristics
The long-term reliability and performance of the
construction materials used for the refurbishment
have a high impact on the expected benefits of the
NZER (Kadam
2001
)
Integration of new and
old building systems
The compatibility issues between new and existing
building systems might result in unforeseen
difficulties and force building stakeholders to
modify design with adverse impact on both cost
and schedule of the project as well as the expected
benefits (Cattano et al.
2012
)
and external uncertainties associated with the construction phase of NZER are
listed in Table
2
.
During project execution of the NZER, construction activities are subject to
considerable uncertainty that may lead to schedule disruptions. This uncertainty
may arise from a number of possible sources, such as integrating some of the new
systems to achieve NZER with existing building systems may take more or less
time than originally estimated, renewable energy systems may become unavailable
due to supply constraints, construction materials may arrive behind schedule, new
activities may have to be incorporated or activities may have to be dropped due to
