Exterior insulation board must extend below grade by how many inches?

Exterior insulation board must extend below grade by how many inches?

• A. 12 inches below
• B. 2 inches below grade
• C. 6 inches below
• D. 8 inches below

Answer: (A)

Extending exterior insulation board twelve inches below grade ensures the thermal barrier continues around the entire foundation, protecting the insulation from moisture, soil, and impact at ground level. This depth helps maintain continuous insulation where the wall meets the foundation, reduces heat loss through the lower edge, and guards against frost and moisture-related damage that can compromise energy performance. The other depths (2, 6, or 8 inches) do not provide the same protection below ground and could allow moisture or mechanical damage to impact the insulation or create thermal bridging near the grade.

Extending exterior insulation board twelve inches below grade ensures the thermal barrier continues around the entire foundation, protecting the insulation from moisture, soil, and impact at ground level. This depth helps maintain continuous insulation where the wall meets the foundation, reduces heat loss through the lower edge, and guards against frost and moisture-related damage that can compromise energy performance. The other depths (2, 6, or 8 inches) do not provide the same protection below ground and could allow moisture or mechanical damage to impact the insulation or create thermal bridging near the grade.