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Page 19
2008-10-01
(3) Using the natural ventilation method requires knowing the volume of the humidified
space and the type of construction. A tightly constructed building will have a least one
air change per hour. A loosely constructed building will have at least one and one half
changes per hour, and this same building with a large a amount of incoming or exiting
traffic will have at least two air changes per hour.
(a) Formula 3
Assume our print shop has a floor area of 100'
x 100' with a 20' ceiling with a
large amount of traffic. This requires
100' x 100' x 20' x 2 = 400,000 ft
3
/hr.
Using our example, the moisture required is
400,000 x 5.08
_______________
= 290 lbs/hr
7000 grains/lb
(4) Using make-up air:
(a) Formula 4
Assume our print shop has a 15,000 CFM HVAC system and uses 10%
make-up air during winter. The amount of outside make-up air entering the
HVAC system will, therefore, be 10% of 15,000 CFM = 1,500 CFM. The
moisture required will be
1,500 x 5.08 x 60 min/hr
_________________________
= 65 lbs/hr
7,000 grains/lb
(Refer to Figure 1.)
Figure 1. Schematic of a Typical Print Shop HVAC System