One of the most critical decisions about the envelope is the contact with the ground. From more abstract types of envelopes to more site specific, the engagement with the ground, the local and its idiosyncracies is one of the qualities of the envelope. The local environment and climate are potentially elements that will be critical to the definition of the envelope. The continuity of the ground and the roof and the envelope as a support of nature, or as a diaphragm that filters the local climatic conditions is one of the capacities that the envelope needs to develop. Often, the potential of the site depends on how the envelope performs in respect to the ground. The envelope can produce an artificial ground and a generic environment or a gradual adjustment to its surroundings. The roof features are crucial to the environmental performance of buildings, producing an extended horizontal limit which provides shelter from temperature, rain and excessive solar exposure. It is also required to allow daylight and ventilation into the enclosed volume.
The relationship with natural environment is crucial, and the ground features prominently in this relationship. The technologies of the envelope can be used to control daylight, airflow and solar intake to produce an adequate atmosphere without having to resort to the radical detachment of interior from exterior.
The envelope can also operate as a new datum, an artificial ground which does not engage in atmospheric continuities but challenges a uniform concept of nature and alters a politically loaded architectural element. The treatment of large-scale roofs as new natural grounds seems to have become a default solution for buildings today as green credentials and organic features have become a favorite with both politicians and urban activists. The use of large flat-horizontal envelopes as grounds, often employed in landscape design, can be found across a variety of programs and locations.