Installing wood stoves into detached houses is becoming popular recently, and is considered to be one solution to realize low-carbon society. Nevertheless, there is few measurements done in Japan to assess indoor thermal environment by wood stoves, making the proper room size heated by one stove unclear. The paper shows the analysis on indoor thermal environment when a room is heated by a wood stove by constructing a detached house with numbers of sensors installed for detailed experiment. After confirming the validity of CFD, methodology to predict proper room size to be heated by a wood stove is introduced.