In the face of climate change and the need to reduce energy consumption, new technologies of building construction and renovation are being implemented. There is a range of building approaches, from “smart” to “efficient”, depending upon how automated the building is (number and kind of sensors and data collected). Nevertheless, the air tightness of buildings is systematically improved in order to increase energy efficiency. The air circulation is controlled and directed by an automatic ventilation system. However, the energy efficiency of the building depends upon the buildings’ users to interfere as little as possible with it (e.g. by opening a window). This presentation aims to question the imaginaries around these “new” technologies of construction, from the perspective of the designers and engineers, as well as the users. We look at the imaginaries of technology, energy transition and human-nature relationship. How are the roles of technologies and users represented? What type of indoor environment is created by airtight buildings? And what relationships to nature and to the world are promoted by these buildings? Airtight buildings were already envisioned in the middle of the 18th century. The promoters of these buildings - the proponents of closed spaces and constant temperature - were opposed to the proponents who favored drafts and temperature contrasts. This debate continued throughout the twentieth century and shows that traditional building was based on other priorities, other criteria of efficiency (healthy air, durability of the building, etc.). Indeed, the current air tightness of buildings raises social, environmental, ethical and health issues - such as air quality (indoor pollution due to building materials, fungi, etc.). We will then discuss the imaginaries of efficiency, and question the pursuit of energy efficiency and its limits.