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Many commercial buildings are moving forward with installing under floor air distribution (UFAD) systems. The UFAD system can provide cost savings to building owners during both the construction and operation of the building. Some major cost savings during the construction stage would include lower costs of mechanical equipment due to reduced fan capacities, smaller air handling unit heating/cooling coil sizes and reduced ductwork. A couple of cost savings from building operations would come from lower electrical load due to reduced fan power, and lower costs for supplying heating / chilled water due to the smaller air handling unit coil sizes. Now to achieve optimal operational cost savings, measures must be taken during the design and construction phases to ensure the UFAD system is designed, installed and commissioned to achieve maximum performance.
Once complete, the raised floor and UFAD system will become a pressurized air plenum which distributes air to the occupied spaces via floor diffusers. To achieve maximum performance of the mechanical systems and provide occupant comfort, the UFAD system must be able to maintain the plenum static pressure and must distribute conditioned air through the installed floor grilles. Any air leakage through holes, gaps, etc. must be reduced to a minimum, and addressed throughout the construction process. As the underfloor plenum is used by multiple contractors for their system components; whether it be mechanical ductwork, electrical cables, data cables, etc., all contractors on the team must be aware that in the end, the raised floor space will become a pressurized plenum which provides conditioned air to building occupants. Having an informed and co-operative construction team will lead to maintaining the construction schedule, and in the end, maintaining building performance.
Minimizing air leakage in the floor plenum is one of the most important factors to ensuring the UFAD system will perform as intended. This becomes a vital part of the construction process, and having the entire design and construction team aware of their duties to ensure the underfloor plenum is sealed properly will help achieve this requirement. To help ensure the underfloor plenum is designed and installed properly, a short list of steps can be followed:
• Ensure project documents specify requirements for sealing the underfloor plenum and responsibilities of the construction team
• Inform all construction team members of the pressurized underfloor system early in the construction stages and explain requirements of sealing the plenum
• Provide list of requirements to the construction team to be met/followed during the construction stages
• Frequently inspect the underfloor plenum space during construction and proactively correct any items which may cause problems during raised floor installation
• Prior to installing floor tiles, ensure underfloor space is clean and free of debris
• Prior to installing floor tiles, ensure all contractors have completed their work where floors will be installed. This may include mechanical, electrical, data, and balancing contractors. Removing floor tiles after installation may create leakage points.
• During installation of floor tiles, ensure any penetrations in the floor system are properly sealed
• Review installation after complete and correct any items of concern
The proper design, construction and operation of a UFAD system can provide superior occupant comfort, but measures must be taken during the design and construction stages to ensure the system is installed properly. Your commissioning agent can help ensure the requirements of a properly installed UFAD system are met and maximize performance of the mechanical systems. In the end, having a system that works will please the building Owner, keep occupants comfortable, and provide positive feedback for the design and construction teams. CFMS can help ensure your underfloor air distribution system is operating to its design intent.