Passive performance of a high-mass residence: Actual data vs. simulation

The public domain building simulation software Energy-Plus® is under development It is to have the capability to simulate radiant cooling and heating panel systems. A recently completed ASHRAE research project (RP-1140) funded the development of a data set for the validation of simulation tools for radiant/convective systems. This study represents an attempt, using these data, to validate Energy Plus' ability to predict a building's performance - in this case, only the passive performance of an envelope-dominated heavy mass residence. Although the case study house happens to have a radiant panel cooling and heating system for which data are available, the simulation accomplished for this paper concerns only the passive operation of the envelope. The logic being that a simulation tool must first be able to predict passive performance if it is to reliably predict active radiant system performance, since the two systems interact. The results were mixed, but most of the simulation results matched favorably with the actual performance for variables evaluated. Various interior temperatures showed the best matches, although there was up to a two-hour shift in highs and lows. The exterior surface temperatures were less reliable with a variance as much as 10°F for the roof surface and a shift up to one-hour in highs and lows for the wall surface. Further work is planned to see if the source of the discrepancy is inaccurate solar radiation component data, direct solar radiation.