Civil Engineering Reference
In-Depth Information
Chapter 5
Performance-Based Standards
A building is made of numerous constructing elements. Each of these elements not
only is affected by and has to face the enforced pressure from the other building
elements, but also has to resist the effects of the environments (both inside and
outdoor). The behavior of these elements when they are facing a combination of
these factors simultaneously defi nes the element performance.
A performance-based standard or code is mainly focused on the outcome and
result of a procedure, product or service and pays either no or at best just a minimum
attention to the how about of the procedures which leads to achieving this outcome.
While a prescriptive standard or code concentrates on detail steps that should be taken
to provide the acceptable products or services as defi ned by that standard or code.
An example of a prescriptive code statement which is the language of the major-
ity of the current codes and standards can be stated like this: “Provide twenty cubic
foot per minute per person (20 cfm/person) outdoor air for the building.” This means
that the code writers have confi dence that in order to have proper outdoor air venti-
lation capacity for a building, it is enough to provide 20 cfm of outdoor air for each
occupant in the building and this quantity of outdoor air can satisfy all the needs for
a clean and healthy indoor environment. While an example of a performance-based
code regarding the same issue can be stated as: “Provide suffi cient outdoor air for
the building to establish a healthy and comfortable environment for the people
staying and functioning in the building. Calculated and distributed enough fresh air
to the spaces based on the space need and usage. Provide monitoring, measuring,
delivering and balancing devices for introducing fresh air close to level of breathing
of people with no short circuiting of the outdoor air through return or exhaust
devices. Ventilation system shall remove all the pollutants from the room.” Of course
at fi rst glance the prescriptive method seems very direct and clear to follow, but as
I stated earlier the performance-based method can invite new invention and advance-
ment in the industry due to allowance for designers to come up with innovations
and newer methods to fulfi ll the design purpose.
