Under Floor Air Distribution
Underfloor Air Distribution

UnderFloorSox (UFSox) is a fabric air dispersion system that improves airflow dispersion within the Underfloor Air Distribution (UFAD) plenum. Uniform temperature within the plenum reduces instances where in floor diffusers are exposed to higher or lower temperatures improving employee comfort.

Underfloor Air Distribution (UFAD) Technology

With initiatives to provide efficient HVAC systems with individual controls, many design teams are turning to UFAD techology. Unlike conventional overhead air-mixing systems, UFAD Systems use the space beneath the raised access floor as a plenum to introduce air into the occupied space, usually through special floor-mounted diffusers.

Typical applications that employ UFAD design are in high tech office and business spaces utilizing cable for voice, power and data transmission. UFAD Systems are becoming increasingly accepted in commercial building space as the benefits, which are well documented by ASHRAE can include:

  • Improved employee comfort
  • Reduced energy costs
  • Improved IAQ
  • Improved productivity and health
  • Reduced floor to floor heights
  • Reduced life cycle building costs

Most UFAD systems are modeled using a Displacement Ventilation principle requiring warm air to rise and stratify from the floor to the ceiling, where it is collected and either exhausted or recycled back into the space. New construction projects using UFAD Technology frequently qualify for LEED® credits for increased ventilation “effectiveness” and individual temperature control.

Graphic provided by Center for the Built Environment, UC-BerkeleyIn concept, supply air is released within the UFAD plenum and is drawn to areas where it is required based on the airflow passing through the adjustable in-floor diffusers. Unfortunately, as air moves from the supply source to perimeter or special high heat load zones, the warmth transferring through the concrete slab warms the air (thermal decay).

When this occurs, occupants in the warmer zones will generally increase the amount of air supply by adjusting their floor mounted diffusers. This can often lead to over mixing the air in the space causing de-stratification and possible benefit loss of UFAD technology.

Graphics provided by Center for the Built Environment, UC-Berkeley

Traditional Solutions

To offset the loss in temperature of supply side air over extended distances, designers have included the use of either air highways, duct work or more supply chases to convey conditioned air to those zones. Although all three have benefits, they all have drawbacks to consider.

More Supply Chases –
Adding supply chases an open floor plan, especially in large projects, can be very expensive and may be difficult to coordinate due to building design and floor layout limitations
Air Highways –
Partitioning the structure and floor tile as duct, air highways can experience significant thermal decay. Additionally, the obstruction can create challenges for routing cable and reconfiguring office space.
Metal Duct –
More comparable of spot cooling metal duct routes and disperses airflow creating uneven pressure and temperature distribution. Systems are not flexible and can create challenges for routing cable and reconfiguring office space.

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