[2] BENEFITS & ADVANTAGES          

WHAT APACS DOES FOR YOU

APACS ADVANTAGES

APACS is the only system that simultaneously allows the individual to control his or her environment and thermostats to control the space.  Total air supply remains essentially the same regardless of personal air outlet settings to maintain control of the space.

The thermostat controls the room;
You control your comfort!

Why Task/Ambient Conditioning (TAC)?

Comfort needs for each person differ and change frequently, causing the the #1 complaint among office occupants.  Task/ambient air conditioning eliminates this problem by providing individuals with personal comfort control.  Tests indicate that the individual can change the temperature he or she feels (the “perceived temperature”) by as much as 8°C by varying the air flow.  Because moving air is doing a lot of the cooling, system temperatures can be set higher to save energy.  People that feel warm simply increase the air flow at their personal air terminals without affecting their neighbors.  In addition TAC provides for cleaner air and saves substantial amounts of energy.

[Click here] for an article on Metabolism from the Mayo Clinic.

[Click here] for a short slide presentation on the advantages of TAC. (Press your browser's Back button to return to this page at the end of the presentation.)

[Click here] for the complete paper, "Why Task/Ambient Conditioning (TAC)?", by Hans F. Levy, P.E. [PDF]

The air required to maintain space conditions can be introduced as displacement ventilation (see Figs. 1.2 below), providing cleaner air to the occupants.  Tests indicate that ventilation effectiveness with displacement ventilation is 1 ˝ to 2 times that of conventional systems.  Results are substantial additional energy savings, especially in hot, humid climates.  All this can be accomplished at lower first cost and much lower life cycle cost.

    INDIVIDUAL CONTROL BY INDIVIDUAL VAV¹

Individual control is necessary and cost effective.  Chapter 8 on Thermal Comfort in the ASHRAE Handbook of Fundamentals indicates vast differences between individual needs for thermal comfort, necessitating individual control.  Professor Ole Fanger demonstrates that personal comfort will lead to greater employee productivity, greater satisfaction and lower turnover.  Employee costs are $300/SF/YR [$2,700/SM/YR] versus $30/SF [$270/SM/YR] for building operations.  The results of individual control are tremendous savings. 

Individual control requires redesign of office buildings.  Since maintaining different temperatures is impractical, varying air velocity (VAV) through personal air outlets is the best method of providing personal control.  Air delivery to every workstation requires access floor.  The result is greater ventilation efficiency, better IAQ, energy savings and increased productivity.

In principle supplying individual air control is simple.  In practice several parameters control the design. 

• ASHRAE Standard 55-2004 limits velocity to 160 FPM [.9 m/s].

• Individual control over air flow reduces air flow to the space.  APACS overcomes this with a common air supply for individual and room outlets.  Reducing individual air flow increases room air flow.

• The air outlet must be very close to the individual
  For low air velocity to be effective;
  To bring air to the individual below room temperature;
  To facilitate individual air flow control;
  To increase ventilation efficiency.

• Supplying air through a pressurized plenum creates leakage to the outside.  Constructing and maintaining airtight buildings is virtually impossible.  The APACS solution is to draw the air from the plenum with fans, resulting in approximately zero pressure in the plenum, preventing leakage to the outside.

By eliminating distribution duct work and taking advantage of other savings, the cost is lower than conventional air conditioning systems.

¹[Click here] for a complete copy of "Individual Control by Individual VAV," by Hans F. Levy, P.E.

* In its Guidelines for Creating High-Performance Green Buildings (1999), the Pennsylvania Department of Environmental Protection notes that "uneven loading conditions combined with the diverse comfort levels of individual temperature preferences and occupant activity levels and their clothing makes a strong case for 'thermally diverse' environments ... A thermally diverse environment allows for a range of comfort tolerances by accommodating different occupant demands."  PADEP recommends designing "systems that have controls for individual occupants" which "help eliminate discomfort and distractions," and "location of thermal delivery units near the occupant ... One example is the use of a raised floor plenum with individually controlled ... air diffusers (Pg. D13)." 

 [Top] [Home]