This paper presents a theoretical study of an integrated radiant floor
heating-direct gain passive solar system. Thermal mass is utilized bo
th for storage of auxiliary heating energy and direct solar gains inci
dent on the floor. An explicit finite difference model is developed to
accurately model nonlinear effects and auxiliary heating control. The
numerical simulation model is employed to study the performance of a
passive solar outdoor test-room with different amounts of thermal mass
under various control strategies with constant and sinusoidal room th
ermostat setpoints. A satisfactory thermal mass is determined based on
energy savings, reduction of room temperature swings, and prevention
of floor surface overheating. Control of auxiliary heating based on a
room effective (operative) temperature is shown to result in improved
thermal comfort and higher utilization of passive solar gains as compa
red to room air temperature control. (C) 1997 Published by Elsevier Sc
ience Ltd.