A system comprising: a combination of at least one building service element and at least one building service-free shaft element for an individual and location independent fastening in front of an outer wall of a building and in particular of an existing building; wherein the building service element has a housing that comprises at least one reception region having preinstalled building service components and a shaft region, and wherein the building service element has a large-area or full-area access opening that is reversibly closed using a closure element and through which the reception region is accessible; wherein the shaft element has a housing that defines a shaft region running from top to bottom, and wherein the shaft region has a large-area or full-area access opening that is reversibly closed using a closure element and through which the shaft region is accessible; characterized in that the system further comprises: at least one reveal element for insertion into a door opening or window opening in the outer wall of the building; and wherein the reveal element has side panels that correspond to a respective edge of the door opening or window opening and that are lined with a heating acting over a large area thereat, with the heating (502, 503) being connected to a building service component of the building service element or to a line conducted in the shaft element for the energy supply, the heating preferably being a heating mat whose heating elements are formed as electrical resistance heatings. a combination of at least one building service element and at least one building service-free shaft element for an individual and location independent fastening in front of an outer wall of a building and in particular of an existing building; wherein the building service element has a housing that comprises at least one reception region having preinstalled building service components and a shaft region, and wherein the building service element has a large-area or full-area access opening that is reversibly closed using a closure element and through which the reception region is accessible; wherein the shaft element has a housing that defines a shaft region running from top to bottom, and wherein the shaft region has a large-area or full-area access opening that is reversibly closed using a closure element and through which the shaft region is accessible; characterized in that the system further comprises: at least one reveal element for insertion into a door opening or window opening in the outer wall of the building; and wherein the reveal element has side panels that correspond to a respective edge of the door opening or window opening and that are lined with a heating acting over a large area thereat, with the heating (502, 503) being connected to a building service component of the building service element or to a line conducted in the shaft element for the energy supply, the heating preferably being a heating mat whose heating elements are formed as electrical resistance heatings. at least one reveal element for insertion into a door opening or window opening in the outer wall of the building; and wherein the reveal element has side panels that correspond to a respective edge of the door opening or window opening and that are lined with a heating acting over a large area thereat, with the heating (502, 503) being connected to a building service component of the building service element or to a line conducted in the shaft element for the energy supply, the heating preferably being a heating mat whose heating elements are formed as electrical resistance heatings.