A program of 27 thermal transmission tests was conducted on 14 different configurations of sheet steel wall. The purpose of the test program was to quantify the heat transfer through the sheet steel wall Z-girts and to evaluate the effects of convective airflow on the heat flow through sheet steel walls. The test walls were 2.44 m × 2.44 m (8 ft × 8 ft) and the tests were conducted in a guarded hot box test apparatus.

The test results showed that the heat flow through the Z-girts could be a significant percentage (35%) of the total heat flow through the sheet steel wall. Approximately half the resistance to this heat flow was contributed by the Z-girt while the other half was contributed by the effective resistance between the Z-girt and the wall faces. The Z-girt heat flow was not significantly reduced by removing half of the screws holding the exterior cladding to the Z-girt but could be reduced if the Z-girt was thermally designed.

The test results also indicated that convective airflow could transport as much heat through a sheet steel wall as was transported by conduction through the insulation. This mechanism of heat transport could be controlled by the addition of an air barrier to the sheet steel wall.

Units: Dual