| Recent warranty claim investigations have identified instances where batt insulation within basement frost walls has slumped and come into contact with the concrete foundation wall. In some cases, this condition has been cited by home inspectors as a potential moisture concern due to reduced drying capacity within the wall assembly. The Building Code requires that moisture-sensitive insulation not be installed in direct contact with concrete foundation walls. Standard construction practice addresses this requirement by offsetting the framed frost wall from the foundation to maintain an air space between the concrete and the insulation. A growing trend has been observed where 2 × 4 frost walls are framed approximately 7 in. from the concrete face to the exterior face of the framing and insulated with R-20 batt insulation. Because R-20 batt insulation typically expands to approximately 6 to 6.5 in. thick, the resulting air space may be limited to only 0.5 to 1 in. In service, batt insulation may slump or bow between studs, further reducing the air space and, in some cases, resulting in contact with the concrete foundation wall. Maintaining a continuous air space between the insulation and the foundation wall improves drying potential and reduces the likelihood of moisture accumulation within the assembly. |
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| To further improve long-term moisture performance and avoid frost wall claims, the following approaches may be considered: |
| 2 × 6 framed frost wall |
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| 2 × 4 framed frost wall with R-20 batt insulation |
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| These recommendations are intended to reduce the potential for claims related to insulation contact with concrete foundation walls, improve moisture management, and reduce frost wall condesnation within below-grade wall assemblies. |
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