Which of the following is not a requirement in Stewarding Materials?

The question is focused on the requirements for Stewarding Materials within the Estidama Pearl Building Rating System (PBRS). Stewarding Materials aims to minimize environmental impact throughout a building's lifecycle by emphasizing the use of sustainable materials. Each of the provided options refers to specific types of materials that can contribute to sustainable building practices.

Recyclable materials are essential because they can be processed and remade into new products, reducing waste and the need for raw materials. Renewable materials are important as they come from sources that can be replenished naturally, such as bamboo or cork, which allows for sustainable harvesting. Reusable materials are also significant, as they can be utilized in new projects without processing, further minimizing waste.

In contrast, while non-polluting materials are desirable and can enhance the sustainability of a project, they are not explicitly required under the Stewarding Materials criteria in the Estidama PBRS framework. The emphasis is more on the lifecycle impacts and the sustainability credentials of materials rather than their potential for pollution. Therefore, the option of non-polluting materials does not fit as a specific requirement within the context of Stewarding Materials, making it the correct answer.