Green Building Materials: How Japan rebuilds and confronts natural disasters

Japan, a nation frequently facing earthquakes, tsunamis, and volcanic eruptions, has continually sought solutions to enhance safety and sustainability in construction. Driven by a strong spirit of innovation, the country has pioneered the use of unique building materials such as volcanic ash concrete, engineered wood, and recycled plastics, enabling structures to better resist seismic activity, withstand water damage, and adapt to harsh climatic conditions.

Could green materials be the key to helping Japan build a safer and more resilient future?

1. Japan: A nation in constant battle with natural disasters

Japan, the beautiful island nation set amidst the vast Pacific Ocean, is renowned not only for its natural splendour but also as a "country of challenges," having to constantly contend with the harsh forces of nature.

Its unique geographical and geological location - situated on the Pacific Ring of Fire and at the convergence of four major tectonic plates - places Japan in a perpetual cycle of earthquakes, tsunamis, and volcanic eruptions.

Moreover, the diversity of its climate and terrain further increases the risk of powerful typhoons, prolonged floods, heavy snowfall, and unpredictable landslides. By mid-century, Japan could face significant economic losses due to the escalating impacts of climate change.

The Impact of Earthquakes in Japan (Source: Internet)

In 2024, Japan faced 100 earthquakes measuring 6.0 magnitude or higher, with the strongest reaching 7.5 on the Richter scale, striking the Noto Peninsula. This event triggered approximately 930 landslides and damaged nearly 169,000 structures. Numerous powerful aftershocks, some as strong as 6.4, continued to follow, significantly complicating emergency response efforts.

Additionally, undersea earthquakes have the potential to trigger devastating tsunamis. The catastrophic 2011 tsunami, with waves reaching up to 56 metres in height, claimed nearly 16,000 lives, destroyed numerous towns, and even led to a severe nuclear disaster at the Fukushima power plant.
Beyond the hundreds of billions of dollars in economic losses, tsunamis have also left profound social impacts, displacing hundreds of thousands of people and causing long-term psychological trauma.

Alongside earthquakes, volcanic eruptions pose a major threat in Japan - a country with 111 active volcanoes, ranking fourth globally. One of the most destructive hazards associated with volcanic eruptions is the pyroclastic flow,  a superheated mixture of gas, volcanic ash, and rock, travelling at speeds between 100 and 700 km/h and temperatures ranging from 200 to over 1,000 degrees Celsius.

The 1991 eruption of Mount Unzen serves as a stark example: pyroclastic flows moving at over 100 km/h claimed 43 lives. Subsequently, accumulated ash transformed into mudflows that swept through residential areas, flooding and causing severe damage to 579 households.

Volcanic Eruptions in Japan (Source: Internet)

Beyond pyroclastic flows, volcanic ash also poses a significant hazard. Although it may not pose an immediate threat to human life, it can seriously disrupt infrastructure and daily activities.
Even a thin layer of ash can halt elevated railway operations. As ash accumulates, especially under wet conditions, it becomes slippery, causing motorcycles, trains, and other vehicles to stall and significantly increasing the risk of accidents.

Moreover, volcanic ash can have a substantial impact on human health. Once airborne, fine ash particles can irritate the eyes, nose, throat, and respiratory system, heightening the risk of bronchial and pulmonary illnesses.

The devastating effects of natural disasters have left a lasting impression on both the Japanese people and government, fostering a deep awareness of the critical importance of safe and resilient infrastructure.
Japan has established stringent building standards, which are regularly updated following each major disaster to ensure that all structures, including rental properties, meet the highest levels of disaster resilience.

The 1968 Tokachi-Oki earthquake and the 1995 Great Hanshin-Awaji Earthquake served as stark wake-up calls, prompting major reforms in building regulations. Key amendments focused on enhancing seismic resilience: from reinforcing reinforced concrete structures, introducing new earthquake-resistant standards in 1981, to improving building codes for wooden houses in 2000 - a common form of housing in Japan.

Notably, Japan’s current three-tier earthquake resistance system is the result of continuous improvements and refinements to the country's building regulations. This system serves as a clear reference framework for the seismic resilience of individual structures, enabling residents and policymakers to make more informed and accurate decisions.

Level 1: Meets minimum standards, capable of withstanding earthquakes of seismic intensity 5.

Level 2: Offers approximately 1.25 times greater resistance compared to Level 1.

Level 3: Designed to the highest safety standards, capable of withstanding forces 1.5 times greater than Level 1.

Japan’s Three-Tier Earthquake Resistance System (Source: Internet)

In addition to seismic resilience, modern building standards in Japan have increasingly incorporated flood prevention measures, particularly in high-risk areas, to ensure comprehensive community safety in the face of escalating climate change challenges.

As global attention on environmental responsibility continues to grow, Japan is proactively shifting towards a more sustainable construction industry. The use of green building materials is becoming increasingly common and is now prioritised in new construction projects.

To accelerate this transition, Japan has introduced certification programmes such as CASBEE (Comprehensive Assessment System for Built Environment Efficiency) - a vital tool for assessing the environmental performance of buildings. CASBEE not only promotes the adoption of eco-friendly solutions but also drives the industry's strong shift towards a sustainable future.

Notably, in 2016, the Japanese government enacted the Act on Improving the Energy Consumption Performance of Buildings, aiming for all new residential and commercial buildings to meet Zero Energy House (ZEH) or Zero Energy Building (ZEB) standards by 2050.

2. Why are “green materials” the answer?

2.1 Environmental benefits of green building materials

According to the U.S. Green Building Council, these materials are considered “environmentally friendly” when they meet the criteria outlined in the LEED (Leadership in Energy and Environmental Design) certification system.

Table 1: Scoring Criteria in the LEED System

Choosing green materials not only demonstrates an organisation’s commitment to sustainable development but also delivers a range of practical benefits, including reduced long-term operational costs, improved user health, and compliance with ESG regulations.

These materials are often designed to enhance energy efficiency, keeping interiors warm in winter and cool in summer — making them particularly well-suited to Japan’s seasonally changing climate. Furthermore, they typically contain fewer harmful chemicals, thereby improving indoor air quality in both living and working environments.

Table 2: Common Green Building Materials and Their Key Properties

Meanwhile, traditional materials such as concrete and steel generate substantial carbon emissions, contributing significantly to global climate change.
Therefore, for a country like Japan, frequently exposed to earthquakes, floods, and volcanic activity, prioritising green materials is not only a sustainable choice but also a critical factor in enhancing disaster resilience.

A notable example is bamboo, a fast-renewing, lightweight material that offers exceptional strength and flexibility, often outperforming steel and concrete in various applications. With these outstanding properties, bamboo is particularly well-suited for structures in earthquake-prone areas. Moreover, it is readily available in Japan at a low cost, easy to transport, and simple to construct with, helping optimise expenses while maintaining sustainability and safety.

Another noteworthy alternative is engineered wood, manufactured from smaller pieces of timber bonded with moisture-resistant adhesives. Thanks to its high resistance to warping and strong load-bearing capacity, engineered wood is not only ideal for earthquake-resistant buildings but also helps reduce carbon emissions by up to 26.5% compared to steel and concrete.

The use of wood also recalls traditional Japanese architecture, where the natural elasticity of the material was fully utilised in ancient constructions. A prime example is the “shinbashira” technique, which involves a central wooden column capable of swaying flexibly, helping ancient pagodas withstand hundreds of years of seismic activity.

Beyond earthquakes, floods also pose a constant threat to Japan. In this context, green materials with water-resistant properties become critical to minimising post-disaster damage. Recycled plastic is a particularly promising example, thanks to its impermeability, resistance to decay, and insect repellence. Notably, the application of such materials also addresses the pressing issue of plastic waste, one of today’s most significant environmental challenges.

When combined with designs such as elevated foundations or flood venting systems, these materials contribute to enhancing disaster resilience and reducing the need for costly reconstruction - thus easing environmental pressures.

In another dimension, Japan - a country with numerous active volcanoes — must pay special attention to building resilience against ashfall, radiation, and pyroclastic flows. Interestingly, volcanic ash, often regarded as waste, can be repurposed to produce volcanic ash concrete a material not only strong and durable but also highly resistant to radiation, addressing both natural waste management and sustainable construction needs.

Additionally, volcanic mineral wool, produced from molten rock, offers exceptional fire resistance, significantly enhancing building safety against dangerous pyroclastic flows. A more innovative approach is Lavaforming directly utilising molten lava to shape foundations and structures, opening up possibilities for seamlessly integrating construction with natural energy exploitation.

Finally, design solutions in volcanic areas are equally critical. For example, roofs should be designed simply to avoid ash accumulation, using materials like standing seam metal sheets to increase durability, facilitate easier maintenance, and reduce environmental risks compared to traditional options.

2.2 Social benefits of green materials for safer and more sustainable development

Green buildings not only benefit the environment but also deliver significant social and economic value. Using environmentally friendly materials such as non-toxic paints, natural wood, and recycled products helps reduce the emission of volatile organic compounds, thereby improving indoor air quality. As a result, the health, comfort, and productivity of building occupants are also enhanced.

From an economic perspective, green buildings often achieve lower operating costs through the efficient use of renewable energy and water. At the same time, they tend to achieve higher asset value compared to traditional constructions, driven by the growing consumer demand for sustainable living.

Importantly, incorporating materials that improve disaster resilience contributes to extending the lifespan of buildings and ensuring greater safety for residents. In this context, the concept of "resilient design", closely associated with green building and sustainable development has become even more meaningful in Japan. Structures designed to recover from natural disasters not only help minimise damage and protect lives but also reduce the need for frequent rebuilding. This results in significant long-term cost savings and further minimises environmental impacts.

This strategic approach reflects a comprehensive vision for sustainable construction, aligning with core principles of sustainable development in the face of accelerating climate change and increasing disaster risks.

3. Leading green building materials in Japan

3.1 Geopolymer concrete from volcanic ash

With its mountainous and volcanic landscape, Japan faces both challenges and opportunities in the pursuit of sustainable construction solutions. In this context, geopolymer concrete has emerged as a highly promising alternative to traditional Portland cement concrete. What sets this material apart is its use of industrial by-products or naturally available resources, such as volcanic ash, as a binder activated through a reaction with alkaline solutions.

Geopolymer Concrete (Source: Internet)

Volcanic ash contains a high concentration of silica and alumina, two key components that react strongly with alkalis to trigger the geopolymerisation process. This reaction involves three main stages: the dissolution of aluminosilicate, the polymerisation of monomers, and the formation of a robust three-dimensional polymer network, resulting in high compressive strength.

A fundamental difference compared to the hydration process of traditional Portland cement is that in conventional cement, water actively participates in forming calcium silicate hydrate (C-S-H). In contrast, in geopolymer concrete, water serves only to facilitate the chemical reaction and does not become part of the final solid structure. As a result, geopolymer concrete is able to maintain superior durability even under high temperatures or harsh environmental conditions.

In terms of compressive strength—the maximum load concrete can bear before failure—geopolymer concrete is comparable to, and can even exceed, that of Ordinary Portland Cement (OPC). Moreover, its faster setting time compared to OPC offers additional advantages, promising to accelerate construction schedules and reduce project time and costs. It is important to note that factors such as the concentration of the alkaline activator and the curing temperature play critical roles in determining the mechanical strength of geopolymer concrete.

One of the most outstanding benefits of geopolymer concrete is its exceptional durability. It exhibits strong resistance to chemical attacks such as acids, sulphates, and salts, as well as harsh weather conditions like freeze-thaw cycles. Thanks to its dense microstructure, geopolymer concrete contributes to extending the service life of buildings, lowering maintenance costs, and delivering long-term economic value.

Additionally, geopolymer concrete typically experiences significantly lower shrinkage during water loss compared to traditional concrete. This characteristic helps to minimise cracking, a common problem in conventional concrete structures, thereby preserving both the structural integrity and the aesthetic appearance of buildings over time.

With an abundant supply of volcanic ash from hundreds of active and dormant volcanoes, Japan holds a significant advantage in the production of geopolymers. Leveraging this "natural waste" not only reduces dependence on traditional raw materials but also helps address environmental challenges following volcanic eruptions.

A prime example is Atelier Tekuto, a pioneering Japanese company that developed a type of concrete using volcanic ash from Kyushu, known as Shirasu, for a project in Tokyo.

The R Torso C house in Tokyo

Shirasu concrete, thanks to its natural pozzolanic reaction, offers high durability and an extended lifespan, outperforming traditional concrete, especially when combined with Volcanic Glass Powder (VGP). Studies have shown that concrete incorporating VGP achieves higher compressive strength at both 7 and 28 days.

Shirasu also exhibits excellent resistance to carbonation and superior waterproofing capabilities due to its dense microstructure, effectively protecting structures from environmental impacts. Moreover, it helps regulate humidity and neutralize odors, contributing to improved indoor air quality.

The R Torso C house is fully recyclable, aligning perfectly with circular economy principles. The project's success has been recognized with several prestigious awards, highlighting the sustainable performance and aesthetic value of Shirasu concrete.

3.2 Engineered wood

Alongside volcanic ash, wood has long been a traditional and familiar material in Japanese architecture. Today, engineered wood is increasingly establishing a prominent position in modern construction, thanks to its seismic resistance and efficient use of wood waste in production. This material is becoming a leading trend in sustainable construction worldwide.

Glulam is produced by bonding multiple layers of timber together with adhesives to achieve the desired length, thickness, and strength. The manufacturing process for Glulam involves several meticulous steps, from harvesting and drying the wood to the appropriate moisture content, to grading and precisely cutting the layers to specification.

Glulam exhibits fire resistance (Source: Internet)

This type of wood boasts a high strength-to-weight ratio, helping to reduce structural loads and limit inertial forces during earthquakes. When exposed to fire, a char layer forms on the surface of Glulam, acting as an insulating barrier that slows down the burning process and protects the internal structure. Additionally, Glulam has low thermal conductivity, contributing to improved energy efficiency. In Japan, Glulam is commonly used for beams, columns, arches, and load-bearing components in structures such as the Hakuryu Dome and the Odate Jukai Dome.

Cross-laminated timber (CLT) is manufactured by stacking and bonding layers of timber boards at right angles to each other, creating panels with exceptional dimensional stability and multi-directional strength. With its excellent thermal insulation, soundproofing, and fire resistance properties, CLT is not only environmentally friendly but also significantly reduces construction time thanks to its high degree of prefabrication.

Laminated Veneer Lumber (LVL) (Source: Internet)

In Japan, LVL is commonly used for beams, girders, and load-bearing components, notably in projects like Port Plus in Yokohama, the country's first fire-resistant high-rise building constructed entirely from wood.

One of the key advantages of engineered wood is its significantly lighter weight compared to concrete and steel. Specifically, cross-laminated timber (CLT) is up to five times lighter than concrete and considerably lighter than other traditional building materials such as stone, brick, and steel. This substantial weight reduction helps to decrease the vibrational energy generated during earthquakes, thus lowering the inertial forces acting on structures.

Products like CLT and LVL, with their multi-layered composition and mechanical connection systems, offer exceptional flexibility and seismic energy dissipation capabilities, outperforming conventional solid wood under dynamic loads.

Port Plus serves as a prime example of how engineered wood enhances structural stability and incorporates seismic isolation technologies to protect the building. Additionally, Takenaka Corporation has developed the T-FoRest product line—combining laminated wood with CLT/LVL, to further improve seismic resistance in construction.

Buildings made with CLT also demonstrate superior seismic absorption capabilities, particularly at mechanical joints, which are traditionally vulnerable points in standard constructions.

Thanks to their two outstanding characteristics—lightweight and natural elasticity, engineered wood materials not only mitigate seismic impacts but also contribute to the sustainable development goals of the construction industry.

The Port Plus building stands as a clear testament to these advancements, being Japan’s first high-rise to use entirely fire-resistant engineered wood. Rising 11 stories (approximately 44 meters), its entire above-ground load-bearing structure, including columns, floor beams, and walls is built with LVL.

Port Plus Earthquake-Resistant Design (Source: Internet)

Port Plus has been specifically designed for high seismic resilience, capable of withstanding Shindo 7 earthquakes the highest level on Japan’s seismic intensity scale. Seismic isolation technology has also been incorporated to further enhance its durability. Notably, a full-scale model of the building successfully passed strong earthquake simulation tests, including a magnitude 7.7 seismic event, without sustaining any structural damage.

3.3 Recycled plastics

Japan, despite its reputation for an efficient waste management system and a high plastic collection rate (80–90%), continues to grapple with the growing challenge of plastic waste a global issue.

To address this situation, the Japanese government has launched a series of initiatives, most notably the "Resource Circulation Strategy for Plastics." This strategy sets ambitious targets: a 25% reduction in single-use plastics by 2030, reuse or recycling of 60% of plastic packaging, and full utilization (through reuse, material recycling, or thermal recycling) of all used plastics by 2035.

Beyond promoting recycling in daily consumer activities, advancing plastic recycling in the construction industry is also emerging as a promising direction. Two notable materials Revia and Replawood, both derived from recycled plastics are expected to play a key role in this effort.

Revia is an advanced, eco-friendly construction material developed by Lixil Corporation, with mass production starting in December 2024. What sets Revia apart is its composition, made from recycled plastic waste (including composite plastics) and wood waste sourced from construction projects, all bonded together using a proprietary adhesive without the need for sorting the input materials.

Recycled Plastics and Wood – Revia (Source: Internet)

From an environmental perspective, Revia significantly reduces CO₂ emissions by 82% compared to incinerating plastic and wood waste and promotes the principles of a circular economy through the recyclability of used Revia products. Additionally, Revia is approximately 50% lighter than concrete, helping to lower transportation costs.

Aesthetically, Revia offers a wood-like feel and texture, with customizable colors and patterns. Lixil is building a comprehensive collaborative ecosystem for Revia, covering procurement, recycling, manufacturing, sales, installation, and product collection.

Replawood, developed by Aitechnos, is a construction material made entirely from 100% recycled plastic. Initially used for concrete formwork, Replawood's applications have since expanded to include outdoor fencing, agricultural and forestry materials, and other exterior structures.

This material is known for its water resistance, high durability, and resistance to peeling, and it can be processed just like real wood cutting, nailing, and planing are all possible. Notably, Replawood does not rot in wet environments and can be ground down and reused multiple times, contributing to a fully closed-loop material cycle.

100% Recycled Plastic Fencing Made from Replawood (Source: Internet)

Similar to engineered wood, recycled plastic materials offer a lightweight advantage particularly valuable in earthquake-prone regions, where reduced structural mass helps minimize inertial forces during seismic events. In areas frequently affected by tsunamis or flooding, using rot-resistant, mold-resistant, and insect-resistant recycled plastics also delivers significant benefits.

However, in structures requiring high load-bearing capacity, such as tsunami-resistant buildings the lightweight nature of recycled plastics can become a limitation. Therefore, hybrid solutions, such as combining recycled plastics with concrete or reinforcing steel, are necessary to ensure both structural strength and adaptability to real-world conditions.

Leveraging recycled plastics, Japan Dome House Co., Ltd. has developed a series of dome-shaped homes optimized for disaster-prone areas affected by earthquakes and typhoons. A remarkable example is from 2016, when Kumamoto Prefecture experienced a devastating 7.3-magnitude earthquake followed by multiple aftershocks as strong as 6.5. While more than 8,600 homes were completely destroyed and over 34,000 severely damaged, the 480 dome houses at Aso Farm Land Resort, constructed from recycled polystyrene, remained standing and undamaged.

Dome Houses Made from Recycled Plastics by Japan Dome House (Source: Internet)

The recycled polystyrene material provides excellent thermal insulation. Coupled with the natural ventilation enabled by the dome shape, these homes achieve outstanding energy efficiency. Moreover, the material is resistant to rust, rot, and termites, and a fire-retardant coating is applied after assembly to enhance safety.

Notably, Japan Dome House emphasizes that their materials are free from formaldehyde (a chemical associated with respiratory issues and skin irritation from prolonged exposure) and include antioxidant treatments, aiming to create healthier living environments. Their products have been tested and certified by Japan’s Ministry of Land, Infrastructure, Transport and Tourism, ensuring compliance with national building standards.

Design flexibility is another key advantage: the modules can be adapted for different uses. As a result, dome houses are not only used as residences but also serve as small hotels, saunas, daycare centers, educational facilities, and karaoke rooms. Thanks to their fast construction times, they are also a promising solution for temporary housing after disasters. Currently, Japan Dome House sells approximately 100 dome houses annually across Japan, demonstrating strong market interest in this housing model.

4. Standardization and certification: How Japan is "measuring" green materials

To achieve its ambitious goal of carbon neutrality by 2050, Japan must implement appropriate policies and standards that foster the development of green materials. Among these, the Comprehensive Assessment System for Built Environment Efficiency (CASBEE) and the Green Product Standards under JIS play crucial roles. These systems provide holistic evaluations, considering everything from a building’s overall performance to the specific environmental impacts of individual construction elements.

4.2 JIS green products: setting industrial standards for environmental consciousness

CASBEE (Comprehensive Assessment System for Built Environment Efficiency) is Japan’s nationally recognized green building certification program. Developed in 2001 by the Japan Sustainable Building Consortium (JSBC) with support from the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), CASBEE currently handles the majority of green building certifications nationwide.

At its core, CASBEE uses the Building Environmental Efficiency (BEE) index to evaluate a building’s environmental performance. BEE is calculated as the ratio of Environmental Quality (Q) to Environmental Load (L): BEE = Q/L. A higher Q relative to L indicates stronger sustainability performance.

CASBEE offers a diverse range of assessment tools tailored to different building types and construction phases, including new constructions, existing buildings, renovations, and single-family homes. Localized versions like CASBEE for Osaka and Yokohama allow for adjustments to regional environmental priorities and challenges, ensuring the system’s flexibility across contexts.

By integrating green material criteria into its evaluation system, CASBEE not only accelerates the shift toward environmentally responsible construction but also significantly reduces carbon emissions. The system encourages material innovation and raises practical environmental awareness among investors, architects, and construction material manufacturers.

This vision aligns with the mission of BambuUP - fostering green innovation as a core driver of sustainable development. As a comprehensive innovation platform, BambuUP enables businesses and corporations to access the resources and insights needed to unlock and effectively apply green solutions, delivering tangible and lasting value.

4.2 JIS green products: setting industrial standards for environmental consciousness

Alongside the CASBEE certification system, Japan also relies on another critical national standard—JIS (Japanese Industrial Standards)—to promote the adoption of green building materials. Overseen by the Japanese Industrial Standards Committee (JISC) under the Ministry of Economy, Trade, and Industry (METI), JIS establishes quality and performance benchmarks across a wide range of industries, including construction.

The JIS framework is divided into multiple sections, with key divisions relevant to construction such as Division A (Architecture and Civil Engineering), Division G (Steel), and Division H (Non-Ferrous Metals).

JIS actively encourages the use of green construction materials through rigorous quality and performance requirements, ensuring that products meet both technical standards and environmental protection goals. For example, standards like JIS A 5021 and A 5022 promote the use of recycled materials in concrete, reducing the extraction of raw resources and facilitating the reuse of construction waste. Meanwhile, standards such as JIS A 9504 and A 9526 focus on ensuring thermal insulation efficiency, helping to lower energy consumption for heating and cooling, and supporting Japan’s broader carbon reduction targets.

Manufacturers of green construction materials can obtain JIS certification through a stringent process that includes product testing and factory audits. Achieving JIS certification provides a competitive edge, enabling manufacturers to build trust and credibility, while also helping consumers make informed decisions when selecting sustainable building materials.

Although JIS compliance is not mandatory for all building materials, possessing JIS certification is a strong indicator of quality and environmental responsibility, significantly enhancing a manufacturer’s market positioning.

Moreover, JIS standards are aligned with international frameworks such as ISO, facilitating global trade and supporting the broader adoption of sustainable construction practices worldwide.

4.3 ZEB/ZEH standards: toward net-zero energy buildings and homes

Beyond evaluating overall environmental performance and the quality of building materials, Japan is accelerating the adoption of standards aimed at achieving net-zero emissions. Among these, ZEB (Net Zero Energy Building) and ZEH (Net Zero Energy House) are two key frameworks designed to minimize the energy consumption of buildings and residences while enabling them to produce enough clean energy to meet their own needs.

Achieving these ambitious goals heavily depends on both architectural design and material selection. Enhancing the insulation performance of the entire building envelope is critical to better controlling thermal flow between the interior and exterior, significantly reducing the need for heating and cooling. Additionally, airtightness is prioritized to minimize the infiltration of outside air, which helps ventilation systems operate more efficiently and conserves energy.

At the same time, the materials used must meet strict criteria regarding carbon emissions, not only during operation but throughout the entire product lifecycle, from manufacturing and transportation to construction.

However, focusing solely on energy savings is not sufficient. ZEB and ZEH-compliant buildings must also be capable of generating their own energy, typically through systems like rooftop solar panels, to offset any remaining consumption. In the case of ZEH, net energy savings after offsetting can range from 75% to 100%, depending on the level of commitment and the solutions implemented.

Finally, for these efforts to be truly effective, all internal systems, including HVAC (heating, ventilation, and air conditioning), lighting, and water heating, must be designed and selected for both energy efficiency and long-term operational stability.

4.4 Financial levers: incentives and subsidies for green building materials

To drive innovation in sustainable green building materials across the construction sector, the Japanese government has not only established standards and certification systems but also implemented a range of practical financial support programs. A notable example is the Earthquake Resistance and Environmental Real Estate Formation Promotion Project, which provides financial assistance for renovation projects that can reduce overall energy consumption by 15% or more, or achieve an A rating under the CASBEE environmental assessment system.

In parallel, the Ministry of the Environment is actively promoting programs aimed at reducing carbon emissions and expanding the use of renewable energy. One standout initiative is the Energy Conservation Promotion Project for Existing Buildings, which supports projects capable of cutting energy consumption by at least 20%. Under this program, subsidies can cover up to one-third of renovation costs, with a maximum grant of up to 50 million yen.

These policies have helped create a comprehensive support ecosystem that not only encourages innovation in material technologies but also attracts proactive engagement from financial institutions. Together, they aim to minimize environmental impacts, enhance asset value, and improve quality of life for communities.

5. The cost and feasibility question: is green really “expensive”?

As government support policies become increasingly clear and comprehensive, one pressing question remains: Is green building material truly cost-effective?

Japan’s construction market is undergoing a significant transformation toward sustainable solutions, with green materials playing a central role. However, when comparing initial costs between green and conventional options, many still perceive sustainable buildings as more expensive. In fact, some studies report that construction costs can increase by an average of 12.5% to 34.06% compared to original budgets.

Pursuing higher certification levels, such as the S rank under the CASBEE system, can also drive up costs by approximately 6.7% to 9.3%, mainly due to limited supply, specialized technical requirements, and certification-related expenses.

On the other hand, some studies suggest that the cost difference is not necessarily substantial. For residential projects, the additional cost is often only around 1.58% to 2%, indicating that green materials can be highly competitive when properly selected and applied.

In the long term, the economic benefits of green materials are significant. Buildings utilizing sustainable materials tend to have longer lifespans and lower maintenance costs, thanks to their durability and reduced reliance on chemical treatments. For example, the Yakisugi wood treatment method not only enhances material longevity but also leads to notable reductions in operational costs.

Moreover, green buildings often demonstrate strong potential for asset value appreciation, reflected in rental premiums of 4–10% and higher occupancy rates compared to conventional buildings. The growing preference among tenants for environmentally friendly living and working spaces, coupled with rising interest from international investors, is reinforcing this trend in Japan’s real estate market.

In conclusion, while the initial investment might pose a short-term hurdle, when viewed holistically with robust government financial support and clear long-term advantages green materials emerge not only as a sustainable and resilient choice but also as a sound economic strategy for the future of Japan’s construction industry.