ASHRAE UFAD O&M GUIDE

Abstract

Scope: Introduction Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings as part of the design of an 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, which is one of the featured characteristics of a UFAD system, allows using warmer supply air than that used with traditional overhead systems. The UFAD cooling load profile is different from a traditional overhead system because of the effect of the raised floor, particularly because systems using UFAD may typically have higher peak cooling loads than those using overhead air distribution. UFAD has several potential advantages over traditional overhead systems, including • layout flexibility, • enhanced individual thermal comfort control, • improved ventilation efficiency, • improved energy efficiency in suitable climates, and • reduced life cycle costs. UFAD is often used in office buildings, particularly highly reconfigurable and open plan offices, where raised floors are desirable for cable management. UFAD is appropriate for various different building types, including commercial office buildings, schools, museums, libraries, etc. UFAD systems have also been used successfully in performing arts facilities and other public meeting venues.