*2.2.2 Revision process of the sustainable design guidelines*

The sustainable design guidelines are necessary to be revised, for adjustment to changing situations and improvement toward higher validity and user-friendliness. We have created the revision process by integrating three factors: (1) changes in the theoretical world, (2) changes in the practical world, (3) user feedback [9]. After making preparations from these three spheres, system designers amend the "element-variable-desired value" expressions.

As demonstrated in the upper left of **Figure 2**, changes over time in the theoretical world are reflected into the design guidelines [9]. First, observing the latest trends in understanding about housing-related problems, system designers amend the problem list. After that, they also modify the list of the requirements for sustainable housing design. When modifying the requirement list, it is also necessary to search for changes in understanding about sustainable housing.

Changes over time in the practical world also need to be taken in the design guidelines. In order to reflect such changes, the system designers observe current trends in housing-related technology and systems related to housing design [9]. In addition, systems related to housing design include compulsory systems, such as building codes, and voluntary systems relating to sustainable housing (assessment and rating systems, standards, guidelines, etc.) [15].

Meanwhile, "user feedback" is significant for the improvement of the design guidelines and checklist. In this case, there are two feedback loops: from system users and home residents. The feedback from the system users is information about reactions to the guidelines and checklist, such as comments on their adequacy and user-friendliness. On the other hand, the feedback from the home residents includes responses to the completed homes, such as remarks about the homes' amenities and sustainability performance [9].
