Civil Engineering Reference
In-Depth Information
to building stakeholders due to the possibility of higher monetary savings during
the life of the building. On the other hand, low energy prices will reduce the
possible monetary benefits that a building stakeholder can obtain from a NZER
(Leckner and Zmeureanu
2011
). Therefore, energy planning is increasingly
important to manage the uncertainty associated with fluctuating energy costs.
Designers can select between off-site and on-site options to achieve the energy
balance keeping in mind that each has its associated uncertainties and risks (Pless
and Torcellini
2009
). For example, off-site sources are uncertain because the
purchasing price of green power could fluctuate significantly due to possible large
demand of green power in the future.
On-site sources are also uncertain because the building stakeholders need to
manage the uncertainties and costs associated with the operation and maintenance
of renewable energy systems. For example, the performance of wind turbines and
PV systems is very dependent on uncertain conditions such as weather and sun
exposure. Moreover, adopting these technologies of high upfront costs could
become difficult because the market for these technologies is constantly changing
from the technological and economic standpoints. Furthermore, reliance on this
type of equipment is affected by the availability of space for their installation.
Energy-renewable installations such as solar panels and wind turbines require large
open spaces for their installation and might not be the best source of renewable
energy for a NZER due to the limiting conditions the project location might impose
(Fong and Lee
2012
; Marszal et al.
2012
; Leckner and Zmeureanu
2011
).
The location of the building will not only affect the availability of sustainable
options, but it will also have a considerable impact on the amount of energy
required for the operation of the building. A building may be designed to achieve
energy balance, but in reality, it may not achieve a net zero-energy balance every
year due to extreme weather conditions. The total energy use variation can be
relatively small, but the energy excess or shortage in relation to the net zero targets
could become significant when the design is performed using historical data
(Robert and Kummert
2012
). Abnormal weather years that have above-average
heating and cooling loads, with below-average solar and wind resources could
greatly affect the performance of the NZER and whether it achieves the energy
balance for any particular year.
All of the above and the lack of information of the past performance of NZEB
make it difficult to design NZER projects and to obtain a clear estimate of the
future costs and benefits.
3.2 Life Cycle Uncertainties: Construction Phase
During the construction phase, a NZER project faces many challenges such as
uncertainty in scheduling, financing, budget management, and unknown preex-
isting conditions among others. All of these directly affect the cost of finalizing the
project within budget and on schedule during the construction phase. The internal
