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On an annual basis, continuously operating air
distribution fans can consume more electricity than
chillers or boilers, which run only intermittently.
High-efficiency air distribution systems can
substantially reduce fan power required by an HVAC
system, resulting in dramatic energy savings.
Because fan power increases at the square of air
speed, delivering a large mass of air at low
velocity is a far more efficient design strategy
than pushing air through small ducts at high
velocity. Supplying only as much air as is needed to
condition or ventilate a space through the use of
variable-air-volume systems is more efficient than
supplying a constant volume of air at all times.
The largest gains in
efficiency for air distribution systems are realized
in the system design phase during new construction
or major retrofits. Modifications to air
distribution systems are difficult to make in
existing buildings, except during a major
renovation.
Design options for
improving air distribution efficiency include:
- Variable-air-volume (VAV)
systems
- VAV diffusers
- Low-pressure-drop
ducting design
- Lowface-velocity air
handlers
- Fan sizing and
variable-frequency-drive (VFD) motors
- Displacement
ventilation systems for air quality.
 As
part of an overall energy upgrade, Wausau West High
School, Wausau Wisconsin, replaced an old
ventilation system with one that introduces 100%
outside air for air quality during heating and cooling operations to
improve indoor air quality and provide a healthy
teaching and learning environment. |
