Typical examples of mitigation and adaptation measures.
In order to meet environmental, social and economic sustainability objectives, an immediate transformation needs to occur in housing design. We have been investigating a methodology for sustainable home design by applying control science because it can be applied to all of goal-oriented tasks. Our first study has shown the basic control system for sustainability. After that, regarding home as the complex of material and spatial elements, we have identified each element’s variables and their desired values that lead to sustainability. Utilizing these schemes, we have composed the “control system for promoting sustainable home design” in which the “sustainable design guidelines” and “sustainability checklist” are incorporated. Following this control system, we have actually designed a home and constructed it. The results of this study indicate that if system users closely follow the methodology, they can design comprehensively sustainable and sufficiently energy-saving homes. Furthermore, the studies imply that this methodology is superior in user-friendliness as well as adaptable to regional differences and changes over time.
- control system
- sustainable housing
- climate change
- ageing population
- material elements
- spatial elements
Buildings including homes have been causing various environmental problems such as climate change, environmental destruction, pollution, and depletion of natural resources. According to the IPCC, in 2010, buildings accounted for 32% of total global final energy use (24% for residential and 8% for commercial) and 19% of all global greenhouse gas emissions . In the twenty-first century, continued emission of greenhouse gases will cause further warming, increasing the likelihood of severe, pervasive, and irreversible impacts on people and ecosystems .
Reducing climate change risks would require both “mitigation” and “adaptation” measures [2, 3], typically shown in Table 1. The chapter of “Climate-Resilient Pathways: Adaptation, Mitigation and Sustainable Development” in
|Mitigation measures||Adaptation measures|
While growing human activities are aggravating climate change and seriously harming environmental sustainability, “ageing population” is becoming a fierce challenge to social and economic sustainability. According to the book titled
It is obvious that an immediate transformation needs to occur in housing design, in order to meet sustainability objectives. Achieving sustainable development or sustainability is the ultimate goal-oriented task of humankind. It is a rational and reliable approach to apply control science to this challenge. Control science can be applied to all of goal-oriented tasks; it has already produced remarkable results in various fields, including engineering .
Based on the above recognition, we have been investigating a methodology for sustainable housing design by applying control science. Our first study has demonstrated the basic control system for sustainability. After that, we have systematically determined the relationships between the elements of home and sustainability. Utilizing these schemes, we have shown the control system for promoting sustainable home design and started putting it into practice. This paper reviews these studies and discusses the characteristics of the methodology and future prospects of our research.
2. Basic control system for sustainability
In the basic control system for sustainability (Figure 1), “controlled objects” are human activities which need to be controlled [10, 11]. “Disturbances” are harmful influences on controlled objects, which are caused by environmental, social, or economic problems. Examples of the disturbances are damaging influences caused by environmental pollution, floods or landslides resulting from environmental destruction, and various impacts caused by climate change. Moreover, “adaptation” has been added as the route from “disturbances” to “sustainability,” based on the recent IPCC’s recognition. “Controlled variables” are the variables that are related to the human activities and need to be controlled for basically solving or preventing the problems or adapting to disturbances.
“Desired values” are derived from the purpose of control, that is to say, sustainability. The model of sustainability (Figure 2) demonstrates that sustainability requires both “fundamental stability” and “internal stability,” in order to accomplish the long-term well-being of humankind or ultimate goal, within the finite global environment and natural resources, or absolute limitations [10, 11]. Fundamental stability means environmental stability and a stable supply of necessary goods; the conditions for fundamental stability are environmental preservation and the sustainable use of natural resources. On the other hand, internal stability means social and economic stability; the conditions for internal stability are health, safety, mutual help, and self-realization, which are essential for well-being of humans.
The control objective is to adjust the controlled variables to their desired values. Furthermore, the control system requires designing and implementing “control measures,” or measures for achieving the control objective.
3. Methodology for sustainable housing design
3.1. Two-step preparatory work
Our previous study has provided the two-step preparatory work for sustainable home design. The two steps are (1) “determining the relationships between the standard home and sustainability” and (2) “sustainability checkup on a home as an object” [12, 13]. The following sections show the essence of these two steps.
3.1.1. Determining the relationships between the standard home and sustainability
In the first step, system designers select important elements of the standard home and determine the relationships between such elements and sustainability.
When selecting important elements, we have analyzed two main factors: “material” and “space” . “Material” regards the home as the aggregate of material elements such as framework, exterior, interior, and piping; “space” considers it as the aggregate of spatial elements, such as rooms and areas. Based on these two factors, we have selected important elements, from which extracts are shown in the central column of Table 2. “Material elements” are from “framework” to “equipment for harnessing natural energy;” “spatial elements” are from “specified bedroom” to “garden area.”
|Relationships with fundamental stability||Element||Relationships with internal stability|
|Condition||Desired value||Variable||Variable||Desired value||Condition|
|Sustainable use of resources||JHPIS 3.1: Grade 3||Durability||Resistance to earthquakes||JHPIS 1.1: Grade 2 or over||Safety|
|Sustainable use of resources||CASBEE LRH2 1.1: Level 4 or over||Materials|
|Sustainable use of resources||CASBEE QH2 1.2 & 3: Level 4 or over||Durability||Fire resistance (outer wall)||JHPIS 2.6: Grade 3 or over||Safety|
|Sustainable use of resources||CASBEE LRH2 1.3: Level 4 or over||Materials||Shape & color||Consideration for the landscape||Health|
|Enviro-preserve Sustainable use of resources||JHPIS 5.1: Grade 4||Thermal insulation performance||Sound insulation performance||JHPIS 8.4: Grade 2 or over||Health|
|Enviro-preserve Sustainable use of resources||CASBEE QH1 1.1.2: Level 4 or over||Sunlight adjustment capability||Protection of glass against impacts||With shutters||Safety|
|Sustainable use of resources||CASBEE LRH2 1.4: Level 4 or over||Materials||Measures against formaldehyde||JHPIS 6.1: Grade 3||Health|
|Enviro-preserve Sustainable use of resources||LED||Type of light|
|Enviro-preserve Sustainable use of resources||CASBEE LRH1 3.2: Level 4 or over||Rainwater equipment||Rainwater equipment||CASBEE LRH1 3.2: Level 4 or over||Health Safety (in crisis)|
|Enviro-preserve Sustainable use of resources||100% or more of the total energy usage||Harnessed natural energy||Harnessed natural energy||100% or more of the total energy usage||Health Safety (in crisis)|
|Routes to toilet & bath area, dining room, kitchen, and entrance||Accessible without steps||Health safety|
|Enviro-preserve Sustainable use of resources||Placing them closer||Areas in the home|
|Differences in level||No differences||Health safety|
|Width||75 cm or more|
|Enviro-preserve||40% or more||Ratio to the exterior area|
After that, we have determined the relationships between these elements and sustainability. The left side of Table 2 shows the relationships between the elements and fundamental stability; the right side demonstrates the relationships between the elements and internal stability. Considering the relationships between each element and the stability conditions, we have identified variables that indicate the degree of stability. Moreover, we have set the desired values of these variables that can meet relevant stability conditions.
Choosing only one element from Table 2, that is, “framework,” I concretely describe the relationships. Considering the relationship between “framework” and “sustainable use of natural resources,” a condition for fundamental stability, we have identified “durability” and “materials” as variables. The desired value of “durability” is set at “Grade 3” in the deterioration resistance grades (building frames, etc.) of JHPIS, that is, the Japan housing performance indication standards (for new homes) . Meanwhile, the desired value of “materials” is set at “Level 4 or over” in the assessment levels of the “use of materials effective for resource saving and waste prevention” of CASBEE, that is, CASBEE for detached houses (for new construction)—technical manual 2010 edition .
On the other hand, considering the relationship with “safety,” a condition for internal stability, we have selected “resistance to earthquakes” as a variable and set its desired value at “Grade 2 or over” in the “seismic resistance grades (prevention of collapse of building structures)” of JHPIS .
In addition, Table 2 is the first updated version, which has been revised due to several reasons. First, we have revised the table so that following it leads to obtain long-life quality housing (
3.1.2. Sustainability checkup on a home as an object
In the second step, “sustainability checkup on a home as an object” is conducted. To be concrete, first, the variables of a home as an object are measured or estimated. Next, the measured or estimated values are compared with the desired values and the comparison results are assessed. Table 3 demonstrates the essence of “sustainability checkup,” which includes an example of the results.
|Relationships with fundamental stability||Element||Relationships with internal stability|
|Desired value||Assess.||Measured or estimated value||Variable||Variable||Measured or estimated value||Assess.||Desired value|
|JHPIS 3.1: Grade 3||No||JHPIS 3.1: Grade 1||Durability||Resistance to earthquakes||JHPIS 1.1 & 1.2: Grade 1||No||JHPIS 1.1: Grade 2 or over|
|CASBEE LRH2 1.1: Level 4 or over||OK||CASBEE LRH2 1.1: Level 4||Materials|
|CASBEE QH2 1.2 & 3: Level 4 or over||No||CASBEE QH2 1.2 & 3: Level 2||Durability||Fire resistance (Outer wall)||JHPIS 2.6: Grade 3||OK||JHPIS 2.6: Grade 3 or over|
|CASBEE LRH2 1.3: Level 4 or over||No||CASBEE LRH2 1.3: Level 3||Materials||Shape & color||Consideration for the landscape||OK||Consideration for the landscape|
|JHPIS 5.1: Grade 4||No||JHPIS 5.1: Grade 1||Thermal insulation performance||Sound insulation performance||JHPIS 8.4: Grade 1||No||JHPIS 8.4: Grade 2 or over|
|CASBEE QH1 1.1.2: Level 4 or over||No||CASBEE QH1 1.1.2: Level 3||Sunlight adjustment capability||Protection of glass against impacts||With shutters||OK||With shutters|
|CASBEE LRH2 1.4: Level 4 or over||OK||CASBEE LRH2 1.4: Level 4||Materials||Measures against formaldehyde||JHPIS 6.1: Grade 3||OK||JHPIS 6.1: Grade 3|
|LED||No||Fluorescent||Type of light|
|CASBEE LRH1 3.2: Level 4 or over||No||No equipment||Rainwater equipment||Rainwater equipment||No equipment||No||CASBEE LRH1 3.2: Level 4 or over|
|100% or more of the total energy||No||0 (zero)||Harnessed natural energy||Harnessed natural energy||0 (zero)||No||100% or more of the total energy|
|Routes to toilet & bath area, dining, kitchen, and entrance||With steps||No||Accessible without steps|
|Placing them closer||OK||Placing them closer||Areas in the home|
|Differences in level||With differences||No||No differences|
|Width||60-70 cm||No||75 cm or more|
|40% or more||OK||45%||Ratio to the exterior area|
In this case, the comparison results have simply been assessed, whether the variable reaches the desired value or not, that is, “OK” or “No.” The variables that have been assessed as “No” need to be identified as “controlled variables.”
3.2. Control system for promoting sustainable home design
Based on the basic control system and the two-step preparatory work, we have composed the control system for promoting sustainable home design.
First, as shown in Figure 3, we have derived two functions from the two-step preparatory work, that is, the “sustainable design guidelines” from step 1 and the “sustainability checklist” from step 2, respectively.
Next, we have composed the control system for promoting sustainable home design in which these two functions are incorporated. Figure 4 demonstrates the block diagram of the control system. In this control system, “controlled objects” include both “new homes” and “existing homes.” The following describes how to use the two functions in the process of sustainable home design, on the order of “new homes” and “existing homes.”
3.2.1. New homes
In the case of new homes, first, information on the desired values reaches “people involved in design” through the “sustainable design guidelines” . “People involved in design” include homeowners, architects, designers, and homebuilders. Such people make a design so that the variables of home’s elements can attain their desired values as close as possible. At important steps in the design process, they check the drawings and specifications by referring to the “sustainability checklist.” After the construction is finished, the new home can be also evaluated against the “sustainability checklist.”
3.2.2. Existing homes
When existing homes are the objects, the design process starts with “inspection” on the home as an object. The “people involved in design” measure or estimate each element’s variables of that home by using the “sustainability checklist.” Next, they compare the measured or estimated variables with their desired values and assess the comparison results.
Table 3 in the last section is equivalent to an example of such inspection results. In addition, when inspecting an existing home and measuring or estimating variables by referring to the JHPIS or CASBEE for detached houses, “people involved” use the “for existing homes” version or “for existing building” version, instead of the “for new homes” version or “new construction” version, respectively. The “JHPIS (for existing homes)” and “CASBEE for detached houses (for existing building)” are almost the same as their new home versions; however, these existing home versions include suitable assessment criteria for existing homes [14, 18].
After the inspection, the “people involved” usually make a design for improvement so that controlled variables meet their desired values as close as possible. When improvement is assumed to be technically difficult or costly, reconstruction can be chosen. Similar to the cases of new homes, they check the drawings and specifications for improvement or reconstruction against the “sustainability checklist.” Moreover, sustainability of actually improved or reconstructed homes can be evaluated against the “checklist.”
4. Case study
Following the above methodology, we designed a new home and constructed it. After this home began to be used, we objectively assessed its environmental performances.
4.1. Design process
In this case, the homeowner, who is the author of this paper, made the basic design by himself. After that, he made a contract with a housing manufacturer whose skills seemed sufficient to achieve the desired values as shown in Table 2.
In the basic design stage, the homeowner used the “sustainable design guidelines” and “sustainability checklist,” in addition to following related laws and regulations. First, when making the site plan and floor plans, he considered spatial elements, such as “specified bedroom,” “areas relating to water use and hot water supply,” and “garden area.” In addition, considering natural ventilation and day lighting, he planned “position and area of windows,” which is omitted from the tables due to space limitations. Moreover, he examined how to install “equipment for harnessing natural energy” and “equipment for rainwater use” so as to satisfy the desired values of these material elements’ variables.
At the beginning of the detailed design stage, the homeowner requested the architects of the housing manufacturer to refer to the “guidelines” and “checklist.” They readily accepted them because the material and spatial elements are equivalent to real parts of the home. Next, we determined the site plan, floor plans, elevation, and fundamental specifications. After that, the architects designed the home’s elements such as framework, exterior, windows and doors, interior, and lighting fixtures, so that as much as possible, the elements’ variables meet their desired values.
After the design stage, we obtained long-life quality housing certification as well as building confirmation. Subsequently, the home, a wooden structure with two stories, was constructed in a residential area of suburban Tokyo.
This section shows the results of the design and construction, focusing on main elements’ variables.
First, Figure 5 demonstrates the site plan and floor plans in which three spatial elements and one material element are referred to:
• Specified bedroom
A “specified bedroom” is a bedroom which is used or expected to be used by elderly or wheelchair users. The owner couple was in their late fifties and not handicapped when they moved in. However, in order to prepare for their future, both their bedroom and other essential areas for their daily living, all have been placed on the same first floor. This arrangement enables them to have access to such areas without any steps.
• Areas relating to water use and hot water supply
“Areas relating to water use and hot water supply,” that is, kitchen, bath, washing room, toilet, and a place to put the water heater, have been placed closer. This planning reduces the total length of water piping and drainage piping. Moreover, this consideration helps to reduce heat loss from hot water piping.
• Garden area
A “garden area” is an area with plants such as trees, shrubs, herbs, grasses and vegetables. The ratio of this home’s garden area to the total exterior area is 67%, which surpasses its desired value, 40%. A larger garden area is favorable for environmental preservation, including mitigation of heat island phenomenon, and a higher level of biodiversity.
This home has been designed so that the “resistance to earthquakes” of the framework meets “Grade 3” in the seismic resistance grades of JHPIS, which surpasses the required level, Grade 2.
The “durability” of the framework satisfies the desired value, or “Grade 3” in the deterioration resistance grades of JHPIS. Grade 3, the highest grade, requires measures to extend the period up to when large-scale renovation becomes necessary after three generations, or about 75–90 years, under normally assumed conditions and maintenance .
As for “materials,” more than half of the wood is domestically produced timber, legality and sustainability of which are authorized. This consideration has sufficiently satisfied the desired value.
Figure 6 shows external appearance, including a panoramic view, with the descriptions of four material elements: exterior, windows and doors, equipment for harnessing natural energy, and equipment for rainwater use.
The “fire resistance” capacity of the outer walls fulfills the desired value, namely “Grade 3” in the fire resistance grades of JHPIS . Meanwhile, the “shape” is simple but accented by the balcony; the “color” of the outer walls, light beige, is coordinated with the colors of other parts, such as the windows and doors, entrance porch, and rainwater pipes. We are expecting that these considerations bring harmony and stability to the landscape.
• Windows and doors
Higher “thermal insulation performance” and “sunlight adjustment capability” of the openings contribute to reducing energy for heating and air conditioning as well as the occupants’ health and comfort [15, 19, 20]. However, both of these variables appear on only the left side of Tables 2 and 3 as the space is limited. The “thermal insulation performance” of this house’s openings meets the desired value, or the highest grade of the relevant item of JHPIS. Meanwhile, the “sunlight adjustment capability” reaches “Level 5” in the assessment levels of the CASBEE’s relevant item. “Level 5” means that the sunlight penetration ratio of the subject windows can be reduced to 0.3 or less in the summer and 0.6 or over in the winter .
We have installed “shutters” on the large windows facing south, in order to “protect the glass against impacts” such as fire, hurricane, and flying objects. This installment is also expected to decrease the risk of being damaged by tornados or huge typhoons, which can be caused by serious climate change.
• Equipment for harnessing natural energy
The surface of the single-pitch roof is almost entirely covered with solar panels. The total generating capacity of the 49 solar panels amounts to 11.4 kW. In the first year, after moving-in, this solar system produced the electricity of 15,911 kWh. In the same period, the energy used in this home has been 3085 kWh. Accordingly, the energy self-sufficiency reached an amazing 516%. This value substantially exceeded the desired value, 100%.
In addition, equipment for harnessing natural energy secures alternative energy sources and increases resilience or passive survivability in crisis. Therefore, it is recognized as an “adaptation” measure as well as “mitigation” [3, 21].
• Equipment for rainwater use
“Equipment for rainwater use,” in this case, a 200-l rainwater tank, meets the desired value. The rainwater in this tank is used for watering the garden, which can reduce the quantity of water supply. At the same time, storing rainwater is also considered one of “adaptation” measures because it leads to securing emergency water supply [3, 21].
Figure 7 illustrates two material elements, namely “interior” and “lighting fixtures,” and one spatial element, namely “doorways.”
Interior, which includes floors, walls and ceilings, requires “measures against formaldehyde” as an important variable. Formaldehyde is a harmful pollutant; therefore, its desired value is set at the highest level of the countermeasures against formaldehyde in JHPIS. All of the interior finish and base materials used in this house are certified materials that meet the desired value.
• Lighting fixtures
All of the “lighting fixtures” of this house use ‘“LED” lights, which meets the desired value.
We have taken barrier-free and universal design into maximum consideration. All of the “doorways” in this home have no “difference in level,” and “width” of the doorways on the first floor except for the bath is 75 cm.
4.3. Performance evaluation
4.3.1. Sustainability performance
After the home started to be used, we had its sustainability evaluated by the “CASBEE for detached houses (for new construction, 2010 edition).” The evaluation results show that the “environmental quality (Q)” and “environmental load (L)” have been “88” and “13” respectively. Consequently, as demonstrated in Figure 8(A), the score of Building Environmental Efficiency (BEE) has reached 6.7, which has rated and certified the home with the highest “S,” or “five stars” .
4.3.2. Energy-saving performance.
We have analyzed the energy-saving performance of this home, by comparing its annual energy usage with that of the average home. The actual total energy usage in this home in a year was 3085 kWh. On the other hand, the average annual energy usage of the same two-person-household detached houses amounts to 41,325 MJ , which is equivalent to 11,479 kWh. The usage of 3085 kWh is equal to 27% of 11,479 kWh. Therefore, as shown in Figure 8(B), this house has reduced energy consumption by over 70%, as compared to the average house under the same conditions.
This chapter discusses the results of this study from the following perspectives: (1) effects of the methodology on achieving sustainable homes, (2) characteristics of the methodology, (3) future work, and (4) applicability of the methodology.
5.1. Effects of the methodology on achieving sustainable homes
As shown in the case study, we have designed a home, following the methodology. To be concrete, we have designed the home’s parts, or elements, so that as much as possible the elements’ variables meet their desired values. After the home started to be used, we have objectively assessed its environmental performances. First, CASBEE for detached houses, a comprehensive assessment system, has readily ranked the home in the highest “S,” with an extremely high score of BEE. Meanwhile, the energy-saving performance assessment has shown that the total energy usage of this home is equal to about 27% of the average home under the same conditions. These assessment results indicate that if system users closely follow the methodology, they can achieve comprehensively sustainable and sufficiently energy-saving homes.
5.2. Characteristics of the methodology
The characteristics of the methodology includes (1) visualization of the processes for promoting sustainable home design, (2) user-friendliness, (3) adaptability to regional differences and changes over time. In addition, the third point is beneficial for the system designers, whereas the second point is convenient for the system users.
5.2.1. Visualization of the processes
Figure 4 has demonstrated the control system in which the “sustainable design guidelines” and “sustainability checklist” are incorporated. It concisely shows processes for promoting sustainable design on both new and existing homes. Moreover, this schematic diagram contains “disturbances” caused by problems, such as climate change. Accordingly, we consider that this diagram itself explains the whole picture of the sustainable design processes with the guidelines and checklist and helps people concerned to recognize them.
The “sustainable design guidelines” and “sustainability checklist” are simple tables. The material and spatial elements in these functions are equivalent to real parts of homes. Therefore, the system users smoothly design, check, evaluate, and inspect the home, by easily comparing the drawings or real home with the guidelines or checklist. In fact, the design process in the case study has supported the user-friendliness of the functions; the designers of the home easily accepted them and efficiently made drawings.
5.2.3. Adaptability to regional differences and changes over time
This methodology originally has a mechanism of easily adapting to regional differences. As shown in Section 3.1., system designers determine the elements’ variables and their desired values, considering the relationships between the elements and sustainability conditions. This determination process has a mechanism of reflecting various regional features, such as natural, geographical, social, and cultural features. For example, a variable of the framework, “resistance to earthquakes,” reflects a geological feature of earthquake-prone Japan. This mechanism also enables the system designers to easily vary the guidelines according to the characteristics of the region. For instance, if the region is in a snowy area or strong wind area, they can adjust the guidelines to the region, by adding “resistance to snowfall” or “resistance to wind” as a variable of the framework.
This characteristic also leads to the flexibility of the functions toward changes over time. In fact, in order to adjust to ageing population, we could smoothly take basic barrier-free design in the guidelines and checklist. To be concrete, we have added necessary spatial elements, such as “specified bedroom” and “doorways.” Similarly, in order to adapt housing to climate change, we have taken adaptation measures in the functions. That is to say, we have added relevant variables including “protection of glass against impacts.”
5.3. Future work
5.3.1. Further case studies
The case study has successfully demonstrated the effects of the methodology on achieving sustainable homes. However, in order to confirm the effects, we need to conduct more case studies, applying it to both new and existing homes. We expect that an increase in the number of case studies will also strengthen the credibility of the methodology and help it to be widely used.
5.3.2. Update of the guidelines and checklist
It is necessary to update the “guidelines” and “checklist,” as the occasion arises. Probably, such revision will have to be made due to several reasons, for example, in response to the results of case studies, changes in the natural and social environment, developments in related sciences, and innovations in related technologies. Furthermore, through such processes, we are planning to examine how to revise them efficiently.
5.4. Applicability of the methodology
This section discusses the applicability of the methodology from two viewpoints: (1) application to other regions, (2) application possibility to other kinds of objects.
5.4.1. Application to other regions
As shown in Section 2, this methodology, specifically the “guidelines” and “checklist,” has a characteristic of being adaptable to regional differences. Therefore, it will probably be easy for system designers in another region to adapt the functions for that region. To be concrete, the system designers can compile its regional version, by examining the elements and adapting the elements’ variables and their desired values to the region’s features.
5.4.2. Application possibility to other kinds of objects
Theoretically, the methodology can be applied to various kinds of objects, or human activities. That is to say, in the control system of Figure 4, “homes” in the block of “controlled objects” can be replaced with other kinds of objects. Possibility of such replacement depends on if the table of relationships, or the “guidelines,” can be compiled or not.
It will not be difficult to apply it to other types of buildings besides the home, since the structure is similar to one another. It is also possible in theory to apply it to other sorts of infrastructure, such as roads and parks. Furthermore, we consider it possible to apply the methodology to more complex and large-scale objects, such as the city and town, for they are also regarded as the complex of material and spatial elements.
The author would like to thank Mr. Vance Carothers for his valuable advice and suggestions on the English expression of this paper.