allowable particle size of 10.0 micron), while the final
Table 5-2
filters shall have a MERV of 13 (80% - 90% efficient with
a maximum particle size of 1.0 micron). Filter racks
Air Intake Minimum Separation
shall be designed to minimize the bypass of air around
Distances
the filter media with a maximum bypass leakage of 0.5
percent.
Minimum
Distance
The placement and location of outdoor air intakes are
Object
m
ft
critical to the safety of the occupants inside a building
Property line
1
3
and must be in compliance with the security requirements
Garage entry, loading dock
7
25
of the building, as described in Chapter 8, Security Design.
Driveway, street or public way
3
10
Table 5-2 provides a guide for minimum separation
Limited access highway
7
25
distances between ventilation air intakes and other
Grade
14
50
building features.
Roof*
0.5
1
Cooling tower or evaporative condensers
5
15
Internal Heat Gain Design Criteria
Exhaust fans and plumbing vents
3
10
Kitchen supply and exhaust air
7
25
Occupancy Levels. For office spaces, the average density
of the occupiable floor area of a GSA building is one
* Roof intakes must be at least 0.2 m (8 inches) above the average maximum
snow depth and the potential for drifts at the intake location must be
person per 9.3 usable m2 (100 usable sq.ft.).Within areas
considered. Outdoor intakes should be covered by 13 mm (0.5 inch) mesh
occupied by workstations, the occupancy load can be as
screen. The screen should be of corrosion-resistant material and located
dense as one person per 7 usable m2 (75 usable sq.ft.) in
outside of or no more that 0.2 m (8 inches) inside of the outside face of the
intake grille, louver, or rain hood entry. On buildings of more than four stories
local areas. Sensible and latent loads per person shall be
the outside air supply louvers shall be located on the fourth level of the
based on the latest edition the ASHRAE Handbook of
building or higher. On buildings of three stories or less, locate the intakes on
the roof or as high as possible. Locating intakes high on the exterior wall is
Fundamentals.
preferred to a roof location. Outside air intake is not permitted within seven
meters (twenty-five feet) of loading dock or any other fume producing areas.
For dining areas, auditoriums and other high occupancy
spaces, occupancy loads shall represent the number of
seats available. Areas such as storage rooms or mechanical
analysis, and the estimated receptacle demand load
rooms do not have occupancy loads.
outlined in Chapter 6.
Equipment Power Densities. Internal heat gain from all
Lighting Power Densities. The rates of heat gain from
appliances-electrical, gas, or steam-shall be taken into
lighting systems shall be based on the latest edition of the
account. The rates of heat gain from equipment shall be
ASHRAE Handbook of Fundamentals or manufacturers'
based on the latest edition of the ASHRAE Handbook of
data.
personal computers, 80 percent diversity shall be
The internal heat gains from lighting systems shall be
considered.
coordinated with, and based on, the electrical load
analysis outlined in Chapter 6.
The internal heat gains from equipment shall be
coordinated with, and based on, the electrical load
123
MECHANICAL
ENGINEERING
5.3
Design Criteria
Revised March 2005 PBS-P100
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