Modeling of delivery efficiency was performed using three levels of combining measured and default input parameters and compared to measured data from seven manufactured homes. Using values based on all measured data provided modeled efficiency results that were closest to short-term coheat efficiency results. As individual measured parameters were replaced by estimated or default values suggested by the draft version of proposed ASH RAE Standard l 52P, the agreement with measured efficiency results worsened. The primary parameters that were varied were the leakage to outdoors and the temperatures in the buffer spaces in which the ducts were located. All of the models gave results that were, on average, within 8 percentage points of measured results. However, simple modifications to the way in which the estimated or default values are obtained would improve the model predictions. It should be noted that many potential default values were not used and that the comparisons were for a very simple type of house, as manufactured homes do not have return duct systems. Additional suggestions are made on ways to improve the determination of input parameters for modeling paths suggested by Standard 152P that were not compared to measured results in this paper.