Effective energy education depends on continuing research designed to identify instructional strategies that will proof effective in particular learning contexts. The aim of this study was to help Taiwanese students learn about energy-saving related concepts through idea-centered, collaborative knowledge-building activities carried out in an online environment. The participants were 34 fifth-grade Taiwanese students. The data were taken mainly from students' online interaction logs and discourse content. We found that knowledge-building activities helped to transform students into more collaborative, autonomous and creative learners, capable of working innovatively with ideas to address the energy-related issues under discussion. The students also demonstrated deeper understanding of the energy-related topics they explored. This study suggests that knowledge-building, an innovative pedagogical approach, was conducive to collaborative learning even in young students.