Civil Engineering Reference
In-Depth Information
radiant temperature), air speed, and humidity. Therefore this standard defi nes these
factors and represents a method for determining acceptable comfort condition in
occupied spaces based on a combination of all these factors. In this method opera-
tive temperature, provisions for humidity control, elevated air speed, air speed
measurement, temperature variations with time, and local thermal discomfort such
as radiant temperature asymmetry, draft, vertical air temperature difference, and
fl oor surface temperature have been discussed as well. Two graphical and computer-
based calculations have been represented to defi ne predicted mean vote (PMV) and
predicted percentage of dissatisfi ed (PPD) people based on the comfort factors that
have been described earlier.
A separate section is dedicated to the method of determining comfort in spaces
that are using natural ventilation with use of operable windows.
Complying with this standard is a major part of any sustainability scoring system
in forms of design, controllability and verifi cation of occupant's comfort. This standard
originally published in 1966 and it has been repeatedly updated and republished
since then.
Outdoor air conditioning is one of the most important and also energy-demanding
parameters in building load calculations, and therefore energy consumptions. The
more extreme the outdoor conditions in heating and cooling seasons are, the higher
is the required energy for conditioning the outdoor air to a proper level that is suit-
able for using inside the building. The main purpose of ASHRAE standards 62
(ASHRAE 2013a ) in addition to defi nition of the different air classes is to make sure
the minimum acceptable air quality for the occupants in a building is provided. In
order to guaranty this condition, the standard specifi es the minimum required out-
door air rate for each space. To specify this rate the standard offers two different
methods of ventilation rate (VR) procedure and indoor air quality (IAQ) Procedure.
Outdoor air quantity based on ventilation rate procedure method is a prescriptive
procedure and is calculated not only based on the type of the application and space
area, but also based on the number of people in the space. In this standard the
method of calculation for the proper outdoor air quantity for different spaces, appli-
cations and density of expected people are discussed. The standard recommends a
combination of fl oor space and people density calculation for every single space in
the building. As an example the standard recommends 0.06 cfm outdoor air per each
square foot of offi ce space plus 5 cfm outdoor air for each person expected to work
in this offi ce. Therefore for an offi ce with 200 square foot fl oor space which is
designed to provide working space for two people the total outdoor air requirement
will be 22 cfm. This quantity of outdoor air should be introduced to the offi ce space
at all time. These calculations should be done for every single space located in the
part of the building that is being served by a single air handling unit, and at the end
the whole quantity of outdoor air for all the spaces should be adjusted in regards to
the most critical space in the system, in order to make sure that all the spaces in this
system receive proper outdoor air quantity.
On other hand IAQ is a performance-based design procedure offered by the stan-
dard as an alternative in which outdoor air intake rates and other system design
parameters are designed to maintain the concentrations of specifi c contaminants at
or below certain limits.
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