*3.2.1.3 Windows and doors*

Openings, especially windows, are related to many requirements for sustainable housing design, including healthy indoor thermal performance. Improving indoor thermal performance requires windows to secure sufficient "thermal insulation performance" and "sunlight adjustment capability," both of which contribute to energy saving by decreasing the demand for heating and air-conditioning [32]. Besides, such tactics also become adaptation measures because they can reduce

temperature-related impacts, including overheating during heat waves [19, 33]. Therefore, we have identified the desired value of thermal insulation performance as "sufficient thermal insulation performance for occupants' health." Meanwhile, the desired value of sunlight adjustment capability has been determined to be "sufficient capability of taking the sunlight in winter and reducing it in summer." Primary factors influencing the sunlight penetration ratio are types of window glass, solar shading materials such as blinds, and eaves. Concerning the windows on the southern façade of the home in **Figure 3**, the window glass, lace curtains, the balcony, the roof with the pendent eave, and the deciduous tree cooperate to control the sunlight.

Moreover, considering an adaptation measure, that is, more impact-resistant exterior, we have specified "protection of glass against impacts" as another variable of windows. Subsequently, we have determined its desired value to be "shutters." Protecting the most vulnerable part of housing external surfaces, namely windowpanes, helps prevent damage caused by climate-related extreme events. As shown in the lower right of **Figure 3**, shutters cover the windows and protect the glass against impacts, such as fire, hurricanes, and flying objects. In addition, covering windows with shutters also helps upgrade intrusion prevention measures.

## *3.2.1.4 Lighting fixtures*

Regarding "lighting fixtures," we have specified the key variable and its desired value as "type of light" and "LED," respectively. LED lamps are significantly more energy-efficient than others, including fluorescent lamps and incandescent lightbulbs; therefore, using LEDs can satisfy energy saving, one of the requirements in **Table 1**. Besides, LEDs are much more durable than other light sources. Furthermore, LEDs do not contain toxic materials, such as mercury [34]. Accordingly, using LED also contributes to reducing environmental impacts related to building materials.

Meanwhile, we have added notes to "LED," saying "lighting fixtures in living spaces are fitted with lighting controls" (**Figure 3**, lower left) [9]. Dimmers and other controls can reduce brightness and help consume only the amount of electricity needed. Thus, LED with lighting controls is highly energy-efficient. Moreover, brightness and color adjustment functions are beneficial for occupants' health and well-being. For example, avoiding bright lights and blue light before bedtime contributes to preventing sleep-quality-related diseases [35, 36].

#### *3.2.2 Spatial element design*

The items shown in the latter part of **Table 2**, namely from "areas relating to water use and hot-water supply" to "green space," are spatial elements. Selecting five from these nine items, this section illustrates spatial element design for sustainable housing.

#### *3.2.2.1 Areas relating to water use and hot-water supply*

"Areas relating to water use and hot-water supply" include a kitchen and hygienerelated area, such as a bathroom and laundry, as well as a place for a water heater (**Figure 4**). These areas should be placed closer, in order to reduce plumbing-related materials and energy. This spatial planning leads to reduction of the total length of water and hot-water plumbing and waste pipes. This consideration also contributes to cutting down the heat loss from hot-water supply pipes. In addition, this arrangement leads to comfort in occupants' daily life. As the distance from the water heater to the faucet decreases, the time until hot water comes out shortens [31].
