The use of digital simulation to evaluate HVAC system energy consumption and building heating/cooling loads has gained wide spread acceptance. These simulations may be divided into two classifications: steady state and dynamic.. The dynamic simulations can be further subdivided into those which consider only the long term dynamics of the system (hour-by-hour simulations) and those which consider the short term dynamics as well. In order to evaluate the effect of room and control system dynamics on energy consumption, it is necessary to retain the short term dynamics of the room and HVAC system and to carry out the simulation with sufficiently short solution intervals to manifest these short term dynamics. The availability of a validated simulation of the short term dynamics would be of interest to the design analyst as well as the researcher. This paper is a summary of the work accomplished in phase one of ASHRAE sponsored project RP 212 monitored by Technical Committee l.4. The objective of this project is to determine the influence of room, equipment, and control system dynamics on energy consumption.