Effects of Duct Improvement and ENERGYSTAR Equipment on Comfort and Energy Efficiency

Residential thermal distribution systems have significant energy and comfort implications due to losses from the distribution system in the form of leakage and conduction and poor distribution from room-to- room within the house. Also, poor mechanical equipment performance, and the interactions between the distribution system and the equipment act to further reduce system capacity and thermal comfort. An example of duct system and equipment interaction is the that airflow over the indoor coils changes the efficiency, capacity and humidity removal of the system resulting in comfort, energy consumption and efficiency changes. To determine if there are any differences in the interactions depending on whether or not the equipment is ENERGYSTAR rated, two houses were tested with standard (SEER10) air conditioners and then retrofitted with ENERGYSTAR (SEER 13) equipment. In addition, the effect of duct leakage was examined by adding leaks to the systems under test. The original plan had been to seal the duct systems, but they were found to be not very leaky. Leakage was added in order to show the effect of reduced leakage. Four additional houses were tested as part of a companion study (Walker et al. (1999)) that did not have equipment changes. Selected measurement results from these houses are presented where appropriate. This report is in two main parts. The first part discusses the field measurement techniques and results. The second part examines efforts to model distribution system performance using a sophisticated computer simulation program called REGCAP. REGCAP has been developed to specifically include the interactions of duct systems with their surroundings (In this study the duct surroundings are attic spaces). Lastly, a brief summary of related thermal distribution system research is included at the end of the report.