Uncertainty in Refurbishment Investment - Nearly Zero Energy Building Refurbishment - page 145

3 Life Cycle Uncertainties in NZEB Refurbishments
NZER buildings are exposed to uncertainties in costs and benefits throughout their
life cycle. Thus, a life cycle perspective is appropriate to identify and classify the
uncertainties that characterize NZER during the design, construction, operation, and
maintenance phases of the building. In addition, these uncertainties can be classified
into two categories according to their sources and the possible control that building
stakeholders have over them. Internal uncertainties are internal to the NZER project
and are within the control/decision of the building stakeholders. On the other hand,
external uncertainties are those beyond the control of the building stakeholders.
Whether internal or external uncertainties, building stakeholders are required to use
appropriate risk management approaches to manage these uncertainties in order to
ensure reliable evaluation results for investment decision-making.
3.1 Life Cycle Uncertainties: Design Phase
During the design phase of NZER, architects and engineers need to decide how
they are going to refurbish their building (e.g., what construction materials they
will use; how they are going to achieve the energy balance through onsite and
offsite use of renewables; and how to integrate with existing building systems).
These decisions need to be made using assumptions about occupant behavior,
fluctuating energy costs, economic benefits, and others. All of these assumptions
affect the success of a NZER project and impact the long-term benefits. Lack of
information about most of these things makes these assumptions a major cause of
uncertainty in NZER design. The internal and external uncertainties associated
with the design phase are listed in Table 1 below along with descriptions of each.
All the uncertainties listed in Table 1 should be evaluated by building stake-
holders during NZER evaluation phase and can be proven to significantly impact the
decision. For example, over 30 % of the energy consumption in high-performance
buildings is related to occupant behavior (Glover 2011 ). However, currently, there is
no proven approach to account for occupancy behavior during the design phase and
its impact on the predicted energy savings and building performance (Marszal et al.
2011 ). In a NZER, the occupant energy consumption cannot be ignored since it can
affect the required renewables to balance the demand, thus increasing the cost of the
refurbishment. If the design team in a NZER project is too optimistic about the
occupants' behavior and their acceptance of new systems and technology
(e.g., occupancy sensors), the refurbished building might not achieve the expected
savings, and the required renewable energy balance might increase (Pless and
Torcellini 2009 ). In addition, the building-related energy usage is constantly
decreasing due to advances in technology; therefore, impact of occupants on total
building energy demand will become increasingly important (Sisson et al. 2007 ).
Another uncertainty that affects NZER during design is fluctuating energy
costs. High energy prices will make the refurbishment investment more attractive