Whilst the current debates on sustainable architecture is dominated by a conversation about energy performance and abstract certification—each easily manipulated to serve commercial gain—I argue that a philosophical reconsideration of relationality is key to a sustainable built environment, examining sustainable architecture through the perspective of Luce Irigaray’s philosophy of being-two. Defining sustainable architecture is a notoriously difficult proposition. Ambitious claims abound, demanding a critical distance, but equally important and necessary self-criticisms are heard. Edward Mazria (2013) founder of the Architecture 2030 Challenge, argues that “life depends on design.” Whilst the building sector as a whole, a major emitter of g...