Civil Engineering Reference
In-Depth Information
studies, multiple objectives were handled by using an aggregate weighted-sum
scalar function. This method suffers from many limitations, such as being
dependent on stated assumptions and on the initial situation. It also provides no
guarantee to reach the best compromise solution according to the underlying
preferences associated with the specification of weights.
2.4 Discussion
In this chapter, an overview of recent research and development related to eval-
uation of different retrofit technologies for building applications is provided.
The major findings from previous studies are as follows:
• A large number of innovative technologies and energy efficiency measures for
building retrofit exist. The main issue is to identify those that will prove to be
the more effective and reliable in the long term.
• The building retrofit assessment procedure is an iterative procedure influenced
by the objectives, the alternative actions, and the sets of constraints.
• The methodologies involving multiple evaluation aspects of potential solutions
for decision support in the assessment of retrofit action may be distinguished
into two main approaches: approaches in which alternatives are explicitly
known a priori (MCDA) and approaches in which alternatives are implicitly
defined within an optimization model (MOP).
• Appropriate problem structuring methods, selection of evaluation criteria, def-
inition of representative alternative courses of action, and preference elicitation
techniques are essential in MCDA approaches to select the most effective retrofit
strategies.
• MCDA approaches consider that a list of predefined intervention solutions is
given for which the performance in multiple (quantitative or qualitative) criteria
is known at the outset. In case a small number of such solutions have been
defined, there is no guarantee that the solution finally reached is the best one
(from the DM's perspective). On the other hand, when a large number of
solutions are defined, the required evaluation and selection processes may
become extremely difficult to handle.
• Recently, more attention has been paid to the use of MOP techniques for the
problem of improving energy efficiency in buildings. These approaches based on
comprehensive mathematical models aim at providing a thorough character-
ization of the trade-offs between different objectives.
• The use of GA to deal with MOP models for building retrofit decision support
has gained an increasing relevance due to its ability to deal with complex
mathematical models and avoid being trapped in local non-dominated solutions.
• A major drawback of the application of GA in building efficiency improvement
is the high number of calls to evaluation function associated with physical
parameters that are generally estimated by an external simulation program such
