Civil Engineering Reference
In-Depth Information
The application ProClim analysed the variation of heat gains for the following
groups of alternatives: façade glazing area (WWR %) varying between 10 % and
80 %, and the orientation of the main façade towards either north, south, east or
west. Heat gains were used as a quantitative indicator to assess the alternatives.
Naturally, the bigger the glazed area, the higher heat gains, which means higher
cooling costs. On the other hand, larger windows may improve a building's
aesthetic properties, but may also make the maintenance of transparent surfaces a
more difficult task. The biggest weights in the group titled 'Window to wall ratio'
(WWR %) were thus attributed to the following criteria: heat gains (0.3) and
comfort (0.2). As the glazed area becomes bigger, the area of other wall con-
structions shrinks, which is why, in terms of a higher price, 'price of glazing'
(0.15) has bigger weight than 'price of wall construction' (0.1). The group of
qualitative indicators includes such indicators as aesthetics (0.15) and maintenance
(0.1). The best option determined by the above weights was the smallest possible
glazed area.
Likewise, the façade orientation towards the cardinal directions (Table
2
) was
assessed against two criteria: heat gains (0.5) and comfort (0.5). Heat gains were
estimated by the application ProClim, but it is a relative figure, which, in our case,
shows the trends in gain variation determined by different orientation. Comfort
was scored in points. In this particular case, the best façade orientation is
northward.
Shading devices are one of the simplest ways to block unwanted sun gains.
Shading devices may control solar gains, block direct sunlight and transmit
diffuse daylight in the room and eliminate glare and high contrast. Fixed shading
devices are usually employed in the building envelope to exclude solar radiation in
the summer and admit it during the winter (Tzempelikos et al.
2007
).
The decision-making matrix in the group titled 'Shading' (Table
3
) analyses
four types of blinds: internal vertical plastic blinds, internal horizontal wooden
blinds, internal horizontal aluminium blinds and external blinds. At any rate, since
blinds are mounted on glazed surfaces, their efficiency to block solar gains, price,
control options and the ease of use, the warranty term, are not the only factors, the
choice of colour and appearance are also important. All quantitative details were
submitted by the manufacturers of shading devices.
In this particular case, the biggest weights were attributed to efficiency (0.3),
price (0.2) and control options (0.15).
The best alternative in this group was internal horizontal aluminium blinds. At
30 %, these blinds had the same efficiency as all other options of internal blinds,
but the lowest price. The efficiency of external blinds to block solar gains is up to
80 %, but the price had one of the biggest weights in the decision support system
and, therefore, it appears to have been the determining criterion in the overall
assessment.
Another feature of the system is multivariate design (Table
5
). It might prove
useful when one needs to make an integrated assessment of all structural and
architectural combinations. The method involves the assessment of the alternatives
from all groups of objects at once considering all weighted criteria defining each of
