How to Insulate Slab Footings for Passive House Performance
By Graham Mann | Published: 1/16/2026
Step-by-step guide to insulating slab footings for Passive House: material choices (XPS, EPS, Polyiso), R-value targets, vapor-barrier placement, and moisture control.
How to Insulate Slab Footings for Passive House Performance To achieve Passive House(https://en.wikipedia.org/wiki/Passivehouse) performance, insulating slab footings is essential to reduce heat loss, improve energy efficiency, and prevent issues like cold floors and condensation. Here's what you need to know: - Why It Matters: Thermal bridging at slab edges can reduce foundation thermal resistance by over 50%, leading to higher heating bills and comfort issues. - Savings: Proper insulation can cut heating costs by 10%-20%, with annual savings of $50-$60 for an 1,800 sq. ft. home in milder climates, more in colder regions. - Materials: Use rigid insulation like XPS, EPS, or Polyiso for effective thermal breaks. Combine with a vapor barrier and protective layers to manage moisture and maintain insulation integrity. - Installation Tips: - Add 2-inch rigid insulation around the foundation perimeter. - Use 10 inches of EPS under the slab for R-50 performance. - Seal all joints and protect ...
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