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Underfloor Technology, or Underfloor Air Distribution (UAD/UFAD), is a method of delivering space conditioning in offices and other commercial buildings. It uses open space between a structural concrete slab and the underside of a raised access floor system to deliver conditioned air directly into an occupied zone of a building. The air is delivered through a variety of supply outlets located at floor or desk level. This method of heating and cooling is quickly growing in popularity due to its potential advantages including improved thermal comfort, increased indoor air quality, and energy use reduction.
Improved Thermal Comfort
This system gives individual users control over their local thermal environment compared to traditional systems. Because ventiliation accessibility, individual comfort preferences can be accommodated. Research evidence shows that occupant satisfaction and productivity can be increased by giving individuals greater control over their local environment. Additionally, UFAD introduces supply air at a higher temperature than overhead systems, reducing the likelihood of cold sensation.
Increased Indoor Air Quality
Three items affect the increased indoor air quality experienced by UFAD users- increased ventilation effectiveness, removal of pollutants out of the breathing zone, and the ability to effectively maintain floor plenums. Ventilation effectiveness is due to the proximity of diffusers to an individual's breathing zone. The overall floor-to-ceiling air flow pattern provided by UAD systems more efficiently remove contaminants from occupied spaces. In other words, air from the floor sweeps pollutants up and away from the breathing zone and reducing cross-contamination. Effectiveness is also increased in cases where users have the ability to relocate/add diffusers to match use patterns of the facility. Ventilation can be increased proportionally to need without awaiting thermal demand.
Taking into consideration factors such as ventilation effectiveness, stratification savings, higher supply temperatures and split task/ambient conditioning, UAD systems can identify between 5-25% energy consumption savings due to use of higher supply air temperatures. These air temperatures allow the use of economizer cycle for longer time, especially in mild climates. For systems that have split task ambient conditioning, savings can occur if task-conditioning operation is flexible and occupancy sensors in use. In addition, UFAD conditions only use the first six feet of space in a room, reducing supply air requirements and chiller and primary fan capacity as a result.
By combining all aspects of the HVAC system into one easily accessible service plenum, flexibility is increased and potential costs are avoided associated with re-configuring building services. Facility management costs decrease due to reduced occupant comfort complaints. These benefits allow for reduction in facility staff requirements and give the team the opportunity to complete preventive maintenance tasks.
Growth for this cost-effective technology has been relatively slow as with any unfamiliar technology. The perceived high risk to designers and building owners, lack of available information and standardized guidelines, and the perceived higher cost of a raised floor drive the resistance to implement UFAD technology.
Feeling unsure about its application? American AgCredit applied UFAD technology to their regional headquarters in Wichita, Kansas and experienced increased employee comfort compared with their previous facility’s traditional system. The award winning system design called for the use of a complementary unit that had the ability to provide very dry, comfortable, underfloor air that cooled slightly into the 60’s. American AgCredit utilized AAON DPAC units because of the product’s ability to efficiently cool all underfloor air while only dehumidifying a portion to lower humidity levels. Learn more.
Interested in how Underfloor Technology could benefit your facility? Contact us to learn more.
Source: Center for the Built Environment: https://www.cbe.berkeley.edu/underfloorair/techoverview.htm