Civil Engineering Reference
In-Depth Information
the energy-efficiency requirements laid out in SAFIERA (South Africa Fenestra-
tion and Insulation Energy Rating Association).
The research from a life cycle perspective was made using SimaPro software.
The determination of carbon footprint was based on IPCC 2007 method, developed
by the Intergovernmental Panel on Climate Change. It contains the climate change
factors of IPCC with a time frame of 100 years. The determination of cumulative
energy demand (renewable and non-renewable) was based on Cumulative energy
demand (CED) method. The decision-making matrix includes alternative options
of external-wall structures (5), glazed units (6), the orientation of glazing (4), the
area of glazing (8) and the shading devices (4).
The group of glazed units comprises of six alternatives with ten quantitative and
qualitative criteria for their assessment (Fig.
10
). Each criterion has its own weight
that shows its impact on the choice of alternatives and the indicator ''±'' that
shows that either higher or lower value of the criterion is better. Quantitative
criteria include thermal transmittance (U value), solar heat gain coefficient
(SGHC), visible light transmittance (VLT), visible light reflectance (VLR), price,
warranty time and longevity. Qualitative include aesthetics, functionality and
comfort.
The presented alternatives of glazing include standard, sun protecting, reflect-
ing glass unit, with neutral, silver or blue tinned glass. Their U value ranges from 1
to 3 W/m
2
K, and SGHC from 29 to 76 %. These parameters are the key indicators
in our case. Lower SHGC cuts heat gains (and cooling demands)—a feature most
significant in countries with hot climates. Lower heat transmittance (U value)
shows greater resistance to heat flow. In order to pick the best alternative from all
glazed units, they all must be assessed by all other criteria, one by one.
The group of external-wall structures comprises of five alternatives with fifteen
quantitative and qualitative criteria (see external wall:
http://iti.vgtu.lt/
imitacijosmain/simpletable.aspx?sistemid=428
)
(Fig.
11
) include thermo-physical
properties, economic and life cycle calculation results of walls materials.
Fig. 10
Initial data of glazing multiple-criteria analysis
