VAV Guidelines - Taylor Engineering

T ABLE 1:
K EY R ECOMMENDATIONS
X2X OVERVIEW
Key Recommendations
The Design Guide presents recommendations that are summarized per Chapter in Table 1
below.
Integrated Design 1. Engage the architect and structural engineer early to coordinate shafts
for low pressure air paths.
2. Work with the architect to evaluate glazing and shading alternatives to
mitigate load, glare and radiant discomfort while providing daylight,
views and architectural pizzazz.
3. Prior to starting the mechanical design for any space, first consider the
potential to reduce or minimize the loads on each space.
Early Design Issues 4. Use simulation tools to understand the part-load performance and
operating costs of system alternatives.
5. Employ a system selection matrix to compare alternative mechanical
system designs.
6. Consider multiple air shafts for large floor plates
7. Place the air shafts close to, but not directly under, the air-handling
equipment for built-up systems.
8. Use return air plenums when possible because they reduce both energy
costs and first costs.
9. Design the HVAC system to efficiently handle auxiliary loads that
operate during off hours.
10. Select a design supply air temperature in the range of 52°F to 57°F.
11. Size interior zones for 60°F or higher supply air temperature to allow
for supply air temperature reset in mild and cold weather.
12. Avoid overly conservative estimates of lighting and plug loads.
13. Consider demand control ventilation in any space with expected
occupancy load at or below 40 ft 2 Zone Issues
/person.
14. For conference rooms, use either a VAV box with a CO sensor to
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reset the zone minimum or a series fan power box with zero minimum
airflow setpoint.
15. Use a “dual maximum” control logic, which allows for a very low
minimum airflow rate during no- and low-load periods.
16. Set the minimum airflow setpoint to the larger of the lowest
controllable airflow setpoint allowed by the box (~10% of design flow)
and the minimum ventilation requirement (often as low as 0.15
cfm/ft 2 VAV Box Selection
).
17. For all except very noise sensitive applications, select VAV boxes for a
total (static plus velocity) pressure drop of 0.5 in. H O. For most
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applications, this provides the optimum energy balance.