Steel conducts heat more readily than wood - for this reason steel stud walls require special insulation details. Insulating sheathing on the exterior side of the wall, with joints and penetrations properly sealed, can improve the thermal performance and reduce the infiltration and exfiltration of moisture-laden air into the wall cavity. Because the steel studs can be below the dewpoint temperature of the air inside the wall it is also important to have a properly installed internal vapor retarder. (See Figure 8.)