Tags: #ASTM #buildingenclosures #buildingenvelopes #buildingmaterials #buildingscience #insulation #materialsscience

Cell structure of insulating materials: visualizing void structures and their vulnerability to air and water.

These illustrations compare pore structure of common insulating materials. When designing rainscreen systems with exterior insulation, it’s important to keep pore characteristics in mind. They largely determine air and bulk water permeability – both affect R-value and both affect the greater wall’s durability. This continually gets lost where materials are not tested with the same methodologies. 

For example, methods for assessing water absorption by foam products employ full water immersion with test durations varying on the basis of material type and intended application: ASTM D2842 (96 hours); ASTM C272 (24 hours); or ASTM C209 (2 hours). In contrast, sorption potentials for fibrous insulation are evaluated in accordance with ASTM C1104, which utilizes water vapor (95 ± 3% RH), not liquid water, as the wetting medium.