This photo is from a recent inspection. You can see where a gas line penetrates a wall top-plate. It is a 1 inch hole with a 1/2 inch pipe, leaving a nice air gap. An air gap like this allows air exchange between the wall cavity and attic reducing indoor air quality and wasting energy. You can also see where fiberglass insulation is missing exposing the sheetrock to the heat and cold of the attic.