Since opening his Milan-based design office in 1972, Antonio Citterio has worked in and across a wide range of contexts—from commercial and residential buildings, to furniture, interiors, and components for companies including B&B Italia, Flos, Iittala, Kartell, Vitra, and more. A longtime collaborator of German brand Axor, the design-driven arm of Hansgrohe, he shares his latest thinking on how product designs for the bathroom can—and should—address sustainability with increasing need.

As an architect, how do you approach the issue of scale, whether you’re working on a building or a fixture

I think about products within a space—as providing solutions for a site. I do not start from the details; I start from the building, then the room. It’s a typical architectural approach. If you design a bathroom, you need certain elements—a bracket, a connector, a rod, and so forth—to create a composition, which leads you to the next step.

Fixtures are long-term designs that are expected to last for decades. What kinds of needs do you take into account when designing them?

In the next 20 years, water, in general, will become a big problem, because we’ll have less and less of it. The big research initiative at Hansgrohe and Axor has been to aerate the water—to put a lot of air into it. It increases the volume of the water, and you consume less of it as a result.

What are some other ways bathroom design can address sustainability?

In this new collection [Axor Citterio E], we tried to reduce the size of both the faucet opening and the handle. When these are made smaller, whether you’re consciously thinking of it or not, imminently, you have a perception of the value of water: It becomes more delicate, more precious. When I designed Citterio M, an earlier collection with Axor, the idea to work with a small, square handle was for the same reason.

Do you think we’ll begin to see such strategies adopted more widely across the industry?

To create buildings in Europe, it’s now a requirement to build sustainably—now we have a law concerning water, limiting it to six liters per flush, no more, because it’s just not possible to do any more building without this facet of performance. To be a truly international company, you must consider sustainability: It’s no longer just the ‘green’ people that are thinking this way. Now, it’s a fact and necessity of life.