A Continuous Air Volume system
uses fans and ducts to distribute air through a large volume of
space. Return ducts then send “used” air back to the fans and
heaters for reconditioning. As the name implies, this type of
system is great for large, continuous spaces, rather than smaller,
divided buildings. One key point of a CAV is that the temperature
and air quality can be precisely controlled. This is important for
hospitals or laboratories.
The multi-zone system (shown
above) separates spaces somewhat like a Variable Air Volume, or VAV,
system. The main large space is controlled exactly like a normal
CAV, but the smaller areas can have their own thermostat and ducting
from the fan.
For example, this would work well
for a theatre, which includes the large hall and a few offices or
dressing rooms. The focus is, of course, on the main performance
hall, so the chosen system would be a CAV. Other examples would be
gymnasiums, auditoriums and factories.
As mentioned above, the key point
of a CAV is that the temperature and air quality can be precisely
controlled. This does have its limitations though. In a VAV,
different areas of a building or space can be controlled
independently, depending on user comfort levels. The multi-zone
system is the most like a VAV of the CAV systems, but not
completely. CAV systems are used in large spaces. Apartment
buildings, schools and individualized offices therefore cannot use
the CAV systems due to their lack of large common spaces.
CAV use the same materials as VAV
and most other typical HVAC systems. A furnace (if you choose
to use that subsystem), aluminum ductwork, thermostats, heaters,
simple or architecturally-pleasing vent covers and fans are all
included as components in Continuous Air Volume Systems.
CAV systems are relatively
expensive to set up, due to the amount of materials needed.
Labor costs will also be high, depending on the size of the space to
be conditioned. In the long run, however, the costs will
decrease (excluding electricity to run the system - that would
depend on the system size and how long the system runs) as long as
the system is set up as efficiently as possible. Maintenance
costs should also be fairly low, as the only real events in the life
of a good CAV system would be an annual cleaning.