The notion of borders as topological and processes could elucidate ecological and social dimensions of sustainability and aid analyses of relations between humans, non-humans and our socio-material world. In this paper we present research based on a detailed case study on a state-of-the-art new neighbourhood with political objectives to display sustainability in the built environment and housing. We focus on glass as a building material and feature to include, exclude, show and hide elements of sustainability in time-space. Some recurring components featuring glass in this neighbourhood are: Felleshus (built as semi-communal ground level buildings, semi-indoor spaces and greenhouses), Wintergardens (built as roof-top semi-private, semi-indoor and social spaces), bicycle storage rooms and spaces for household waste recycling. When humans and non-humans interact in different practices relations are dynamic and constantly negotiated; bordering processes indicate that borders are made and remade. Topological understandings of borders show how quieter registers of power find reach into this neighbourhood and homes. Political definitions of ecological and social dimensions of sustainability are found in different socio-material versions, often including glass as a feature to aid desirable bordering processes. These processes may sometimes invite sustainable interactions between humans and non-humans, sometimes reject interactions. We argue that despite the solid state of glass, it could be enacted for making ecological and social dimension of sustainability fluid and partly open, partly closed for different versions of sustainability.