What is Rigid Foam Board Insulation?

What is Rigid Foam Board Insulation?

Rigid foam board insulation consists of stiff panels made from various foam materials including polystyrene, polyisocyanurate, and polyurethane. These boards provide continuous insulation, excellent moisture resistance, and high R-values in relatively thin profiles.

Types of Rigid Foam Boards

Expanded Polystyrene (EPS)

• R-3.6 to R-4.0 per inch
• Lowest cost option
• Good moisture resistance

Extruded Polystyrene (XPS)

• R-5.0 per inch
• Excellent moisture resistance
• Higher compressive strength

Polyisocyanurate (Polyiso)

• R-6.0 to R-6.5 per inch
• Highest R-value per inch
• Often faced with foil or fiber

Key Benefits

• Continuous Insulation: Eliminates thermal bridging through framing
• Moisture Resistance: Won't absorb water or lose R-value when wet
• Dimensional Stability: Maintains shape and performance over time
• Versatile Application: Suitable for walls, roofs, and foundations

Installation Methods

Rigid foam boards can be installed using various methods:

• Mechanical Fastening: Screws with large washers or specialized fasteners
• Adhesive Application: Construction adhesive for certain applications
• Foam Adhesive: Spray foam to seal joints and attach boards
• Furring Strips: Attached through foam to structural elements

Best Applications

Performance Comparison

Installation Considerations

Proper installation requires attention to air sealing, vapor management, and local building codes. Some foam boards may require thermal barriers when used in interior applications. Professional installation ensures optimal performance and code compliance.