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Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings as part of the design of a HVAC system. UFAD systems use an underfloor supply plenum located between the structural concrete slab and a raised floor system to supply conditioned air through floor diffusers directly into the occupied zone of the building. Thermal stratification is one of the featured characteristics of UFAD systems, which allows higher thermostat setpoints compared to the traditional overhead systems (OH). UFAD cooling load profile is different from a traditional OH system due to the impact of raised floor, particularly UFAD may have a higher peak cooling load than that of OH systems

UFAD systems rely on air handling units to filter and condition air to the appropriate supply conditions so it can be delivered to the occupied zone. While overhead systems typically use ducts to distribute the air, UFAD systems use the underfloor plenum formed by installation of a raised floor. The plenum generally sits 0.3 and 0.46 metres (12 and 18 in) above the structural concrete slab, although lower heights are possible.[3][4] Specially designed floor diffusers are used as the supply outlets.[5] The most common UFAD configuration consists of a central air handling unit delivering air through a pressurized plenum and into the space through floor diffusers. Other approaches may incorporate fan powered terminal units at the outlets, underfloor ducts, desktop vents or connections to Personal Environmental Control Systems.

Underfloor Air Distribution System revolutionizes your environment with improved ventilation, air quality, occupant productivity – all at a lower cost to operate.

An underfloor air distribution system offers

  • 1. Upto 30% lower energy use
  • 2. Improved ventilation and air quality
  • 3. Improve office productivity
  • 4. Lower life cycle cost
  • 5. Easier access to building services


  • 1. Flexibility for relocating wiring, piping, and other building services
  • 2. Reduce energy use
  • 3. Improved ventilation and Indoor air quality
  • 4. Documented improvements in occupant comfort, productivity, and health
  • 5. Reduced slab-to-slab height and facade costs

Projects using advanced service distribution solutions have reduced installation costs by up to 10% and achieve 15% faster build and completion times. There are many areas where first costs can be neutralized, for example:

  • • Design Flexibility – Adapts to existing or new architectural features, uneven floor
  • • Laminated Finishes – Applying floor finishes such as wood, stone, and linoleum in the factory saves labor and materials cost
  • • Voice/Data Cabling – Reduce cable run lengths, eliminate cable trays and lower labor costs at installation. Relocating cables becomes easier for a lifetime
  • • Power Wiring – ‘Plug & Play’ technology significantly reduces installation costs
  • • Furniture – Eliminate dependency on expensive powered furniture and improve space planning options
  • • Air Distribution – Significantly reduce trunk, branch, and discharge ductwork, lower first cost
  • • Ceiling – Reduce or eliminate suspended ceiling requirements
  • • Time to Occupancy – Underfloor services install quickly, allowing for earlier occupation
  • • Structure – Improved integration of underfloor services provide slab-to-slab height reduction opportunities or taller occupied space


  • • Enhanced indoor environmental quality through superior IAQ, improved acoustics, and increased daylighting opportunities
  • • Maximum occupant comfort control at design inception and throughout the life of the building using underfloor air with modular ‘plug & play’ VAV or manually controlled diffusers
  • • Energy efficiency through economizer operation, and 30% less fan energy
  • • Easily adapts to technological and organizational changes over the building’s lifecycle at low cost
  • • Point-of-use services wherever you need them with complete flexibility, accessibility, and unlimited capacity
  • • Accelerated tax depreciation opportunities; UFAD and floor is FF&E (7 years amortized)
  • • Reduced first cost and construction time due to significant reduction (typically 75%) in HVAC ductwork and use of underfloor prefabricated ‘plug & play’ wire/cable services
  • • Reduced operating expenses and lower facility and maintenance costs through accessible, flexible, and adaptable services


Architects are always challenged to improve the indoor environmental quality of the buildings they design. This requires striking the perfect balance between function, aesthetics, efficiency, health, and comfort.

Under Floor Air Distribution and raised access floors help architects meet these challenges by:

  • • Manufacturing with high levels of recycled content, minimizing the environmental impact
  • • UFAD reduces energy use and provides advanced personal comfort control
  • • Raised access floors improve a building’s overall functionality and provide access for quick service changes
  • • More than 10 LEED Points are achievable by proper application of raised access floors and UFAD, resulting in a better return on investment (ROI)


Underfloor Air Distribution offers a unique opportunity for improving indoor environmental conditions. It saves operating costs by increasing outdoor economizer hours, lowering fan horsepower and increasing the granularity of space temperature control.

Key engineering benefits of Underfloor Air Distribution Systems:

  • • ASHRAE 62.1 ventilation code recognizes the displacement ventilation of well-designed UFAD systems as providing 20% better ventilation effectiveness (Ez)
  • • UFAD can help achieve better ventilation effectiveness by supplying the air closer to the occupants
  • • Proximity cooling also improves personal comfort control by allowing the occupant to adjust and control their micro-climate individually
  • • UFAD is also an effective strategy for improving energy efficiency, attenuating noise, responding to organizational and technology changes quickly and easily
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