**2.1 Control system for promoting sustainable housing design**

The control system for promoting sustainable housing design is shown in **Figure 1**. The upper and lower sections separated by the dotted line are the "theoretical world" and the "practical world."

In **Figure 1**, "controlled objects" are homes, which include both new and existing homes. "Disturbances" mean adverse effects on controlled objects originating from environmental, social, or economic issues. Instances of the disturbances are impacts of pollution and extreme weather events caused by climate change. The route from "disturbances" to "sustainability" is "adaptation." Recently, the

**Figure 1.**

*Control system for promoting sustainable housing design.*

necessity of adaptation to disturbances has become widely recognized, along with the progress of climate change [1]. The IPCC has stated that achieving sustainability also requires adapting to climate-related impacts, in addition to mitigating climate change [11].

The control purpose is the accomplishment of "sustainability." The upper-left box in **Figure 1** shows that achieving sustainability requires fulfilling both environmental and well-being conditions. Environmental conditions are "environmental preservation" and "sustainable use of natural resources." Meanwhile, well-being conditions are "health," "safety," "mutual help," and "self-realization," which are significant factors for people's well-being [12].

"Controlled variables" are the variables that are related to controlled objects and should be controlled for mostly solving or preventing the issues or adapting to disturbances. On the other side, "desired values" are derived from the control purpose, namely sustainability. The control objective of this control system is to adjust the controlled variables to their desired values [13, 14].

In the practical world, the subjects of control are "those involved in design," including homeowners, designers, architects, and homebuilders. In order to adjust the controlled variables to their desired values, those involved in design utilize the "sustainable design guidelines" and "sustainability checklist." Both of the design guidelines and checklist have almost the same expressions, that is, elements, variables, and desired values. However, the checklist is formed to smoothly compare measured or estimated values of the variables with the desired values and search for controlled variables [13, 14].

When objects are new homes, information about the desired values reaches "those involved in design" through the "sustainable design guidelines." Those involved prepare "drawings and specifications" so that the variables of the home's elements can satisfy their desired values to full potential. At significant phases in the design work, those involved in design check the drawings and specifications by seeing the "sustainability checklist" [13, 14].

When objects are existing homes, the design work starts with "inspection" on the home as an object. Using the sustainability checklist, "those involved in design" measure or estimate each element's variables of that home. Next, they compare the variables' measured/estimated values with the desired values. As a result, the variables whose measured or estimated values fall below the desired values should be "controlled variables." After the inspection, those involved in design usually prepare "drawings and specifications" for improvement so that the controlled variables meet their desired values to the maximum [13, 14].

### **2.2 Production and revision process of sustainable design guidelines**

**Figure 2** demonstrates the process of producing and revising the sustainable housing design guidelines and sustainability checklist. The upper section of the diagram is the "theoretical world," and the lower section is the "practical world."

The four blocks on the left side are the items that system designers refer to when producing or revising the sustainable housing design guidelines. The central part shows the flow of planning and using the sustainable design guidelines and checklist. First, the system designers produce or revise the design guidelines through the three-stage process. Subsequently, system users employ the design guidelines and checklist. Finally, the residents use the completed homes that have been designed with the design guidelines and checklist. Meanwhile, the two items on the lower right show the feedback loops from the system users and home residents.

**Figure 2.**

*Process of producing and revising the sustainable housing design guidelines and sustainability checklist [9].*

#### *2.2.1 Production process of the sustainable design guidelines*

The production process of the sustainable housing design guidelines is made up of three stages: (1) identification of environmental, social, and economic problems related to housing, (2) identification of the requirements for sustainable housing design, (3) determination of elements, variables, and their desired values in the sustainable design guidelines [9].

In the first stage, system designers identify environmental, social, and economic issues related to housing, while checking trends in understanding about such issues. The basis for the identification is that the issues affect the well-being and environmental conditions shown in **Figure 1**, such as health, safety, and environmental preservation. System designers can specify local/particular issues in their country or region, in addition to global/general issues [9].

Next, based on the specified housing-related issues, the system designers identify the requirements for sustainable housing design. When identifying such requirements, it is useful to observe trends in understanding about sustainable housing [9].

In the third stage, the requirements for sustainable housing design are converted into a table of "element-variable-desired value," which can be found in the design guidelines. First, the system designers select "elements" so as to cover significant and necessary parts of homes. When selecting elements, it is helpful to base two factors on: "material" and "space." "Material" considers homes as the complexity of material elements, including framework, exterior, interior, windows and doors, and plumbing. "Space" regards homes as the complexity of spatial elements, such as rooms and areas [13, 14]. After identifying elements, system designers specify the elements' "variables" that can show the directions of the requirements for

sustainable design. Subsequently, they determine the variables' "desired values" to meet the requirements.

The most significant advantage of converting the requirements into the "element-variable-desired value" table is practical convenience to system users. "Elements" in the table correspond to actual parts of homes. "Variables" and their "desired values" show the design points and their targets, respectively. Therefore, the system users can easily understand what should be designed and design steps [9].
