How to Insulate Slab Footings for Passive House Performance Use the Slab-on-Grade Insulation Calculator(/tools/slab-on-grade-calculator) to compare R-10, R-15, and full sub-slab strategies side-by-side: F-factor(/glossary/f-factor), annual heating cost, and payback vs an uninsulated baseline. To achieve Passive House(https://en.wikipedia.org/wiki/Passivehouse) performance, insulating slab footings is essential to reduce heat loss(/glossary/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 bar...