The Korean folk house has created a comfortable indoor environment with passive control of outdoor climate as an example of environmental architecture. This study aims to identify the peculiar elements of environmental architecture in folk houses in Cheju Island and Ullung Island through field experiments. The elements of environmental control of folk houses in both islands could be developed as design elements of modern architecture. This effort can play a major role to find the passive design principles and techniques of environmental control of the building which have been neglected in the design of modem architecture.