For example, consider filling a nominal joint width of 2.00 inches with a
nominal 4-inch width, nominal 4-pcf density insulation. The effective
density at the nominal joint width is 8 pcf. Unlike static perimeter
joint protection, the effective density of a dynamic perimeter joint
protection changes when the nominal joint width changes. When
the nominal joint width decreases the effective density increases.
Conversely, when the nominal joint width increases the effective
density decreases. The maximum reduction in effective density
occurs at the maximum joint width. The change in the effective
density is expressed as follows.
The 8-pcf effective density at the nominal joint width decreases to
5.3-pcf effective density at the maximum joint width. This condition
is the worse-case test scenario as it allows a greater heat transfer
through the insulation.
Conclusion about Movement Cycling Test: While ASTM E2307
allows both static and dynamic perimeter joint protection installations,
a greater level of life safety can be achieved by specifying and testing
the more severe and necessary condition: dynamic perimeter joint
protection.
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