Civil Engineering Reference
In-Depth Information
During the conceptual design phase of a building, the design team often has to
make critical decisions with significant impact on the energy performance and
indoor comfort conditions. The design and selection of facades, fenestration sys-
tems and their control plays a key role in determining building performance
(Tzempelikos et al.
2007
).
The presented decision support system covers the following groups of objects:
six glazed units, five external-wall constructions, eight different areas of glazing,
four orientations of the main façade towards the cardinal directions, and four
shading devices. Each of these alternatives makes a considerable impact on a
building's energy demands, indoor comfort, aesthetic properties and, naturally,
price. Hence, the alternatives will be defined by both quantitative and qualitative
criteria. For each criterion, the decision support system sets a measuring unit
(qualitative criteria are scored in points) and the weight [e.g. price (0.1)]. Bigger
weight means the criterion is more significant. The indicator '±' shows that either
higher or lower value of the criterion is better. One by one, each group of objects is
considered, its alternatives are analysed against the defined criteria and their
weights, and then, the best option is picked out. The utility degree of each alter-
native is then considered and the alternatives are ranked as a first priority, second
priority and so on.
Some indicators were determined theoretically (such as the thermal transmit-
tance coefficient, inertia, etc.), some were obtained from the manufacturers of the
materials (such as optical and thermal properties of windows, prices, etc.). Two
software applications helped determine the balance of heat gains and the values of
quantitative indicators to be used in the assessment of the life cycle of materials:
• Proclim. This application created a reference model of a single-zone building
(7 9 5 9 2.6 m) in Johannesburg (South Africa). By varying wall construc-
tions, optical and thermal properties of glazed units, building's orientation
towards the cardinal directions and the glazed area, the software determined
typical daily gain balances. Since a universal assessment much depends on the
intensity of gain variations, this figure will be included as a quantitative indi-
cator defining the alternatives in question, as it is important in their assessment.
The assessment trends of the properties of building's windows and walls
correspond to the recommendations laid out in South Africa Fenestration &
Insulation Energy Rating Association (SAFIERA).
• SimaPro. It is one of the most popular applications designed to assess the life
cycle of building materials. Two methods—IPCC 2007 and Cumulative Energy
Demand (CED)—were selected to assess each material used in the construction
of walls. IPCC 2007 GWP 100a method lists the climate change factors of IPCC
with a timeframe of 100 years. Here, the total amount of carbon dioxide
equivalent
emissions
over
the
production
life
cycle
(kg
CO
2
-Eq/kg)
was
determined for each structural material in its production phase.
• The CED represents the direct and indirect energy use in units throughout the
life cycle. In our case, CED. Renewable and CED. Non-renewable were
determined to assess the external-wall materials in their production phase.
