Japan’s sustainable clay roof tiles kawara suitable for climate change

Japanese temples and shrines have stood for hundreds of years, weathering typhoons, snowfalls and scorching heat days. The elegant clay tiles known as “kawara,” adorned with intricate decorations, have graced rooftops for 1,400 years, prized for their fire and water resistance.

Three main kawara-producing regions are Aichi (home of Sanshu Kawara), Hyogo (where Awaji Kawara come from) and Shimane (known for Sekishu Kawara) Prefectures. Among them, Sanshu Kawara is the most frequently used, occupying 70% of the kawara market share. These Sanshu Kawara producers have now begun to transform this traditional industry to meet today’s waste reduction and climate change challenges.

Redesigning tile-cutting method to reduce waste

Eishiro-gawara Co., the oldest kawara manufacturer in business since 1801, realized that as much as 400 kg of tiles per house had been wasted in the process of trimming them to fit unique shapes of each roof. In 2005, the company began to pre-cut karawa tiles in its in-house factory, instead of chopping them on the job site and dumping unused parts in a landfill.

The pre-cut method has reduced overall waste, allowing tiles with imperfections (e.g., with scratches and chipped corners) to be used for smaller pieces. In addition, workers have been spared from the noise and dust of clay sewing on rooftops, which is not only a health hazard but a safety concern. The pre-cut method is now an industry best practice.

Repurposing used kawara to make something “cool”

Another innovation is to reuse crushed and grounded tiles, “chamotte,” for new tilemaking and as a groundcover. About 80% of tiles with imperfections can be recalcined as clay. Scrap tiles from tile manufacturing process or re-roofing and demolition can also be repurposed in a similar manner.

Compared to artificial land-covering materials, such as asphalt, crushed Sanshu Kawara chamotte is water-permeable and heat-releasable. A study has already found its cooling effect, which improves the outdoor thermal environment, especially in the summer, as the global temperature continues to rise.

Sanshu Kawara’s sustainability model highlights the synergy between tradition and innovation. We may not need to look too far for a solution, only if we could tweak what we have taken for granted.