937Strategies for Reducing Heat Loss in Metal Building Walls

9.3.7.1 Maintain Maximum Spacing Between Z-Girts Tests on a 10-inch wall8 with a theoretical R-value of

36 hr-ft2-°F/Btu demonstrated a measured R-value of 10.2 hr-ft2-°F/Btu with the girts spaced 2 feet apart. Increasing the spacing to 8 feet between the girts had a corresponding effect of increasing the R-value to 16.5 hr-ft2-°F/Btu. While typical girt spacing in the wall of a metal building is 6 feet on-center, this study does emphasize the desirability of maximizing the girt spacing wherever possible.

9.3.7.2 Use "Thermal" Girts

The thermal performance of metal building walls can be improved by the substitution of thermally improved Z-girts. The use of expanded "thermal" Z-Girts has the potential to increase the effective R-value by 1520% for a wall with Girts spaced 8 feet apart.4 A significant amount of the metal has been removed from these thermal girts, which increases the length of the heat flow path and reduces the girt's heat flow area. Figure 9.10 indicates the basic structure of such a girt.

Figure 9.10 Expanded "thermal" girt.

Figure 9.10 Expanded "thermal" girt.

Table 9.3 Wall insulation installed between 16 gauge Z-girts.

Nominal

Table 9.3 Wall insulation installed between 16 gauge Z-girts.

Nominal

Unbridged

Thickness

R-Value

R-Value

R-Value

R-Value

R-Value

R-Value

(Inches)

2, O.C.

4' O.C.

5, O.C.

6, O.C.

8, O.C.

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