ASHRAE research project RP-787 was a computational study of the factors that influence heat transfer in ceiling and floor plenums. The heat transfer phenomena in plenums are complex and include conduction, convection, and radiation modes. The public domain nodal program HLITE was used in the project to find the steady-periodic cooling loads in typical office/plenum spaces. A companion program, VLITE, was used to solve the radiation view factors. Three-dimensional models of ceiling and floor plenums with six different air distribution schemes were examined. Common fluorescent luminaires were modelled in significant detail. The sensitivity of plenum models to various parameters such as convective heat transfer coefficients, surface conditions, and other parameters was found and is presented. The required accuracy is given for each variable to which the computer models were sensitive. Recommendations are made for additional research to determine the effects of ceiling and floor plenums on peak cooling loads and for developing design guidelines

KEYWORDS: year 1997, Heat flow, ceilings, floors, plenums, calculating, heat transfer coefficient, computer programs, cooling load, offices, air distribution, suspended ceilings, elevated, fluorescent lamps, accuracy, air distribution, offices, lighting producing heat