During September, October, November, and December 2005, two 2x4 wood framed walls insulated with R-13 (3.5-in. thick) fiberglass batts were tested in the Oak Ridge National Laboratory (ORNL) guarded hot-box using ASTM C-1363 procedure. These wall assemblies were built on request from the Lennar Family of Builders with increased amount of framing members.
According to the report prepared in 2002 by Enermodal Engineering for California Energy Commission, there is 27 percent framing in current residential walls in California. A similar study performed by ASHRAE in 2003 has concluded an average 25% of framing factor for all US residential buildings. Two wood framed test walls were following the CEC and ASHRAE projects findings. In these walls 2x4 studs were installed either at 24-in. or at 16-in. on center as shown on Figure 1. The amount of framing members for all these walls was between 22% and 25%. Conventional ½-in. thick OSB sheathing and ½-in. thick gypsum boards were used for exterior and interior wall finish. Detailed dimensions of test wall specimens are presented on Figures 2 and 3.
Figure 3. Layout of the test wall with studs installed at 16-in. O.C.
Personnel fromthe ORNL BTC constructed all test wall assemblies on site. All wood framing members were installed according to specifications showed on Figures 2 and 3. Cavity insulation (R-13 fibreglass batts) was custom-cut for each wall configuration to ensure the perfect fit - as shown on Figure 4. The exterior surfaces of the test walls were then faced with ½-in. thick OSB sheathing. The interior surfaces of the test walls were then faced with ½-in. thick layer of gypsum board.
Figure 4 . Test wood framed wall after installation of the fiberglass insulation.
The completed test wall measured 8-ft. wide x 8-ft. tall and was positioned in the test frame such that the wall was centered both vertically and horizontally over the metering chamber opening. The bottom and top tracks were even with the bottom and top metering chamber gaskets.
The chamber conditions for this test were 100°F and 50°F in the metering and climate chambers, respectively. Array of thermocouples were installed on the both hot and cold sides of the test walls. The arrays for both surfaces were installed to monitor temperatures over the wall cavities, over the studs, over clusters of studs, and over the top and bottom track. The average temperatures of the hot and cold wall surfaces were determined by averaging all of the thermocouples attached to the individual components. An area weighting method was used to determine overall external average surface temperatures. The weighting factors used for the individual components will be discussed later in this report.
Figure 5 shows the typical wall installation schedule within the test frame. The area of the test frame surrounding the specimen wall on both sides and the top was filled with expanded polystyrene insulation to the same thickness as the test wall. The entire perimeter of the test wall was caulked and taped to prevent air leakage.
Figure 5. Schematic of the installation of a typical wall within the hot-box test frame.
For More Information Contact Dr. Jan Kosny