*3.1.5 Insufficient considerations for working at/from home and learning*

Recently homes have been becoming more significant as working places [9]. The development of information technology and networks has been promoting homebased businesses [7]. Besides, an increasing number of firms are adopting working from home [7, 8]. Meanwhile, life longevity is increasing the necessity of lifelong learning [28]. As a result, housing is also gaining importance as a place of learning for adults as well as children.

Previously, houses were not recognized as significant places of working and lifelong learning. Accordingly, if attempting to start working or learning at home, people often encounter difficulties due to a lack of space and facilities. In fact, unexpected demands for working from home forced by the COVID-19 pandemic revealed such difficulties. For example, in April of 2020, a housing-related firm in Japan, Recruit Sumai Company Ltd., conducted a questionnaire to office workers living in the Greater Tokyo Metropolitan area and gained 1390 valid responses. As a result, many workers from home answered that there were various insufficiencies in their houses, such as a lack of space or room for working and equipment shortages [29].

#### **3.2 Conversion into housing elements, variables, and desired values**

We have converted the requirements for sustainable design into the structure of housing elements, variables, and desired values. First, based on the abovementioned two factors, namely "material" and "space," we have selected a total of 23 housing elements. After specifying the elements, we have determined variables and their desired values, as shown in **Table 2**.

#### *3.2.1 Material element design*

In **Table 2**, material elements are from "entire building" to "outdoor facilities." Choosing four from these 14 items, this section illustrates material element design for sustainable housing.

#### *3.2.1.1 Entire building*

The shape of the entire building closely relates to the "energy saving" and "material saving" shown in **Table 1**. Preferring compact forms to sprawling ones reduces the building envelope surface area and decreases thermal transfer through the surface [18, 30]. Moreover, pursuing compact shapes also leads to lower embodied energy and environmental impacts related to materials for constructing the envelope itself [30]. Therefore, we have identified the entire building's key variable and its desired value as "shape: compactness" and "compact," respectively.

The most common quantitative indicator of compactness is the ratio of the envelope surface area (S) to the enclosed volume (V) [30]. Accordingly, we have adopted the "surface-to-volume ratio (S/V)" as the index of the variable and determined its desired value as a "smaller S/V ratio." For example, the S/V ratio of the house shown in **Figure 3** is 0.888, which is a considerably small figure among S/V ratios of shapes with the same enclosed volume as this house. When planning this home, the owner and designers pursued a more compact form in the restriction of the shown narrow land.

*Sustainable Housing Design: System Control Strategy DOI: http://dx.doi.org/10.5772/intechopen.100126*



*relating to water use and hot-water supply" to "green space".*

#### **Table 2.**

*Sustainable housing design guidelines for general use.*

#### *3.2.1.2 Equipment for harnessing renewable energy*

Responding to "use of renewable energy," a requirement for sustainable housing design, we have identified "equipment for harnessing renewable energy" as a material element. After that, we have determined the key variable and its


#### **Figure 3.**

*An example of material element design for sustainable housing [31].*

desired value to be "harnessed renewable energy" and "100% or more of the total energy usage," respectively. This desired value means aiming at net-zero-energy or surplus-energy housing. Achieving the desired value usually needs both energy saving and a considerable equipment capacity to harness renewable energy.

The most common equipment for harnessing renewable energy on housing sites is solar power generation systems. For example, the house demonstrated in **Figure 3** is equipped with 49 solar panels on the single-pitch roof. The combination of this largerscale photovoltaic generation system and various energy-saving schemes has enabled this home to reach an amazing 500% of self-sufficiency in energy [31].
