This presentation will provide a look at some of the most important design issues that come to the fore when implementing a hydronic biomass boiler system. Segueing from fuel supply and storage considerations (the topic of the first part of the workshop), we will proceed to discuss boiler sizing and thermal storage in biomass systems. Advantages of multiple-boiler systems for varying load profiles will also be discussed. When these issues are understood, biomass hydronic systems are at their most efficient and provide an excellent alternative to fossil fuels or other renewable energy sources such as solar thermal for heating purposes.