Insulation materials, granulated: Air permeability (NT BUILD 360)

  • Report #: NT BUILD 360
  • Approved: September 1990
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The objective of the test method is to determine coefficients which describe the correlation between the linear air flow velocity through insulation materials and the pressure drop in insulation materials.


The method may be applied to granulated insulation materials where the granules have a shape which allows the main part of the air flow to pass through the air cavities between the granules. The method is only recommended for granules with a typical smallest dimension of 5 mm or larger. The method is especially intended to be used for testing such types of insulation materials that are used in constructions where a certain amount of ventilation is necessary to reduce the humidity. Examples of such constructions are low crawl spaces or roofs completely filled with insulation material. Insulation for these purposes requires air permeabilities within certain ranges.

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