Center for the Built Environment

This paper summarizes the assumptions and equations behind a new spreadsheet-based cooling load design tool for underfloor air distribution (UFAD) systems developed by the Center for the Built Environment at University of California, Berkeley. After briefly reviewing previous UFAD design tools, we describe in detail how the design tool: a) transforms the zone design cooling load calculated for a standard overhead (OH) mixing system into the design cooling load for a stratified UFAD system, accounting for differences in design day cooling load profiles for OH and UFAD systems; b) splits the total UFAD cooling load into three fractions, supply plenum (SPF), zone, or room, (ZF), and return plenum (RPF); c) manages the thermal comfort in a vertically stratified environment; d) predicts the air temperature profiles and the setpoint temperature at the thermostat; eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide. e) models the air diffusers; f) predicts the design airflow rate; and g) models commonly used plenum configurations.