as beams and light fixtures that could divert supply air directly
on the occupants. Linear slot diffusers are important in VAV
systems (refer to Appendix C).
a) Louvers are used to admit supply air, discharge
exhaust air, or admit return air to the ductwork system. Often
these are detailed on architectural drawings and installed under
architectural sheet metal because the architectural designer
wants to control the esthetics of the building exterior.
Consider the following in placement of intake louvers so they
(1) Not exposed to blowing dust, driving rain,
high winds, auto exhaust fumes (loading docks), embanked snow, or
cooling towers, and industrial exhaust stacks (25 foot minimum).
(3) Away from building entrances where radiated
noise from the fan equipment could be annoying.
(4) Away from building exhaust air, building
plumbing vents, and odors from kitchen hood exhausts, and
b) In the design of louver blades, a proper compromise
must be made between maximum net free area and trapping of
windblown rain. See Figure 9 for a typical rain resistant
c) Keep air velocities low through louver intakes to
avoid noise and excessive pressure drops. Compute pressure drop
based on the percent of free flow area for the louver and the
pressure drop through insect and bird screens.
d) For industrial ventilation systems with fume hoods,
makeup air should be introduced through a perforated ceiling,
ceiling panels, or perforated ducts to distribute the air
uniformly throughout the room.
Filters for HVAC Systems. Use high efficiency filters
only if the mission requires clean air since they cost more to
install and maintain, take more space, and use more energy. High
efficiency filters should be preceded by pre-filters to extend