As in Phase I, the specimen walls for this series of tests were built and supplied by the National Association of Home Builders Research Center (NAHBRC). All test walls for this phase measured 96-in. x 96-in. Some of the wall assemblies (test samples) were damaged during shipment to Oak Ridge National Laboratory (ORNL), necessitating a visit to the Buildings Technology Center (BTC) by NAHBRC personnel to evaluate the damage and to make the necessary repairs. The biggest concern with the damage was the collapsing of the slits in the slotted studs, thereby reducing the effectiveness of the conduction break in the path across the stud flange. Care was taken to assure that all slits were opened to their original spacing. After repair, the walls nonetheless retained some minor cosmetic damage consisting primarily of dimples and dents. NAHBRC and BTC personnel concluded that these cosmetic blemishes would have negligible affect on the thermal performance of the framing.
The initial test plan for this phase called for a total of five walls to be tested in ten different configurations. However, two additional walls were added toward the completion of testing. The test configurations consisted of nominal 2x4 cold-formed steel-framed wall assemblies and nominal 2x4 slotted-stud walls, with the common characteristics of 0.5-in. thick gypsum board on the warm side, 0.5-in. thick oriented strand board (OSB) on the cold side, and full-width R-13 craft-faced fiberglass batt insulation in the cavities. Wall 2 was an exception and utilized a 1-1/2-in x 1-1/2-in x 20 gauge galvanized steel strap placed horizontally across the studs and 1-in Tuff-R polyisocyanurate insulation in place of the 1/2-in OSB on the exterior side. Wall 6 also varied from the other walls in that the OSB was replaced with 20 gauge galvanized steel sheet and the cavity insulation was unfaced R-15 batts.
Variations of the base walls tested included modified track/stud combinations and application of foam sheathing on the exterior OSB wall surface. Walls 2 through 4 and 6 through 7 utilized a split track design which consisted of removing a portion of the center track web to within 1-in of each bend. The missing center portion provided a thermal break in the conduction path of the track. The top track for wall 5 used a modification of the split track design. This modification was applied to the top track only and consisted of a split track mounted to a nominal 2x4 wood stud. The bottom track was identical to the split tracks used in walls 2-4. The 2x4 used in this wall was part of the metered area, causing the metal studs to be 1-1/2-in shorter than the studs in the other walls. Wall 3, used in tests 6 and 7, was fabricated from solid web studs.