High-efficiency, condensing boilers have been available in the U.S. since the 1990s and are now common in the residential market, but in many instances are not achieving consistent condensing performance levels due to high return water temperatures. This is particularly true with hydronic baseboard heating systems and their traditional sizing and design methods. In high performance, low-load homes, a change in the baseboard sizing and overall system configuration iswarranted.

In response to this need, Steven Winter Associates, Inc. (SWA) teamed with the Department of Energy's Building America Program, the New York State Energy Research and Development Authority (NYSERDA), Ithaca Neighborhood Housing Services (INHS), and Brookhaven National Laboratory (BNL) to evaluate the performance of condensing boilers using baseboard convector delivery systems. Specific objectives included: 1) evaluate and define the optimal operating parameters of the condensing-boiler/hot-water baseboard combination; 2) evaluate and define the optimal operating parameters of the condensing boiler/indirect domestic hot water combination; 3) test those findings in real-world residential settings; and 4) document those parameters in a technically accurate, installer friendly manner. This research identified several issues affecting: 1) the installed performance of condensing boilers when combined with baseboard convector; 2) the comfort of the occupant; and 3) the longevity of the equipment. This presentation outlines the test protocol used for evaluating system performance in three homes in the cold climate region, key findings from over one year of data collection, suggestions for improving installed efficiency, and continuing research needs to overcome market barriers.