This research explores the capabilities of EnergyPlus to predict the sailing season performance by comparing the actual data recorded at a high-mass residence at Carefree, Arizona, with the simulated results using EnergyPlus, for two sets of data recorded during fall 2000 and spring 2001. The research compares the various data elements recorded at the site, namely interior and exterior surface temperatures, interior air and operative and mean radiant temperatures, with that of simulated results. The study was conducted by creating a custom weather file, which was modified from the original Phoenix TMY2 file by replacing the essential data with that of actual data recorded at the site. The results indicate that EnergyPlus predicts various surface temperatures, air temperatures and operative temperatures of a passive high-mass residence within an average accuracy of 1-3°F compared to that of the observed data. Although the temperature trend predicted by EnergyPlus closely matches the actual data, the temperature lag predicted by EnergyPlus tends to consistently deviate from the observed data by 1 to 2 hours. The study requires further analysis using experimentally derived material properties and an accurate solar-radiation data in weather file to enhance the accuracy of the simulation model.

Low temperature radiant cooling systems are generating a lot of interest among energy and HVAC professionals. The ability to predict the effectiveness and the energy efficiency of these systems has been a long-standing goal for designers. These studies have been limited by the absence of simulation tools capable of accurately analyzing these systems. An accurate analysis of such systems requires the accurate prediction of the transient nature of the combined radiant and convective heat transfer processes. A simulation tool called EnergyPlus, aimed at incorporating all of these characteristics, is under development at the University of Illinois and was used for this study.


The performance data of an instrumented residence using radiant panels was used in an attempt to validate the simulation capabilities of EnergyPlus. The building under study is a high mass residence in Carefree, Arizona that uses a hydronic radiant cooling system embedded in the ceiling and the floor. The focus of the study was to identify the heat transfer processes taking place within the house. The aim was to establish the radiative, convective and conductive processes taking place at each surface of the residence -- the walls, floor, glass, etc. After the affect of the radiative and convective heat transfers processes was quantified, this information was to be used to determine the optimum amount of thermal mass for this system in the house.
The successful completion of the study relied on the successful validation of EnergyPlus and its capacity to simulate radiant systems. This was to be achieved by the comparison of simulation results with the data collected on site. The study revealed that EnergyPlus has good potential to become a powerful tool for analyzing radiant systems. In its current stage of development, EnergyPlus was able to predict the passive performance of the house but it was unable to model the radiant system accurately. At this stage in its development, EnergyPlus is not able to incorporate the control strategies defined by the user. Thus, the full study could not be completed but the work did identify some important limitations in the tool, and put forward recommendations that would be useful for the further development of EnergyPlus.