The use of underfloor air delivery systems in conjunction with raised access floors has had rapid growth in the past few years. Underfloor systems are capable of improving air quality and occupant comfort levels as well as extending the service flexibility of the raised floor platform to encompass the mechanical services to the space. However, care must be afforded during the design of these systems to avoid unnecessary obstructions in the floor (service delivery) cavity if the flexibility of the raised floor system is to be optimized. Temperature control and zoning strategies that provide superior occupant comfort yet maintain the integrity of the open floor cavity should be favored.This paper discusses many of the issues and available alternatives to accomplishing this. Particular emphasis is directed toward the differences in controlling interior and perimeter zones.Units: SI