Sustainability isn't only about the products and systems you use. I had a house renovation in University Place, WA where we could have done a big addition, but through a creative re-configuration of the floor plan we were able to "win back" a lot of underused space. The sustainability of NOT building more than you need gets you the biggest bang for your buck. It isn't always the obvious solution.
As a design choice, one of the best water-saving features we've been in cooperation implementing on a project has been a dry-lay porcelain tile system with a water harvesting feature below. This is a patented UK built system that can be used to save water for use in a full ecosystem. From water off your patio to water features, ponds, green walls and incorporated planters on your patio, a full system which enhances design. The steel frame system is fully manufactured off site reducing wastage to nothing on site and reducing delivery to 1 delivery per project and time on site. Working with the Keystone tiles, specifically a range with low surface tension, reducing pooling on the outdoor tiles. An amazing design combination. Design | Inspire | Create