1. The exterior "skin" of your house consists of:
A. The porch and front steps.
Your view of "skin" was much too limited to make the cut. These are simply two features of the house that contribute to it. Broaden your vision, and please remember for the future well-being of your historic house that the exterior "skin", or weather envelope, typically includes all the surfaces of its functional and decorative features--roof, chimney, exterior walls, woodwork, windows, porches, doors, and the foundation walls. This "skin" serves as the primary defense against the potentially damaging effects of sun, rain, snow, ice and wind. So taking care of the outside of a house and all those interconnecting surfaces between parts is of critical importance. Simply, it's how you preserve the historic character. If the "skin" is not properly maintained and repaired, you may have to replace an entire feature, and at great expense!
Stand corrected and try the next question...