Rigid Foam Insulation
Rigid foam insulation consists of stiff panels of polystyrene, polyisocyanurate, or polyurethane foam that provide superior insulating value and moisture resistance for walls, roofs, and foundations.
Rigid foam insulation boards deliver high R-values in minimal thickness, making them ideal for applications where space is limited. Three main types dominate the market: expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (polyiso). XPS provides R-5 per inch, polyiso offers R-6 to R-6.5 per inch, and EPS delivers R-4 per inch. Unlike fiberglass batts, rigid foam maintains its R-value when wet and provides excellent air sealing when joints are taped.
Why It Matters for Energy Efficiency
Rigid foam excels in continuous insulation applications—installed on the exterior of wall sheathing or under roof decking, it eliminates thermal bridging through studs and rafters. This continuous thermal break can improve whole-wall R-values by 20-40% compared to cavity insulation alone. For Denver basement remodels, rigid foam on foundation walls resists moisture while insulating, and won't support mold growth. Modern energy codes increasingly require continuous insulation, making rigid foam essential for code compliance.
Common Applications
- Exterior wall sheathing: 1-2 inches over OSB for continuous insulation
- Foundation walls: 2-4 inches on interior or exterior for basement insulation
- Under slab: Insulating concrete slabs in heated spaces
- Cathedral ceiling: Above roof deck in unvented roof assemblies
- Perimeter insulation: Around slab edges and frost-protected shallow foundations
Related Terms
R-Value
R-Value measures the thermal resistance of insulation materials, with higher values indicating better insulating properties and greater energy efficiency.
Vapor Barrier
A vapor barrier is a moisture-impermeable material installed in building assemblies to prevent water vapor from penetrating walls, floors, or ceilings and condensing within insulation or structural components.
Energy Code Compliance
Energy code compliance involves meeting minimum standards for insulation, air sealing, window performance, and HVAC efficiency as mandated by the International Energy Conservation Code (IECC).