Rigid Foam Board Insulation
Rigid foam board insulation consists of stiff panels of insulating foam that provide high R-values and versatility for various applications, including continuous exterior insulation to reduce thermal bridging.
Composition
Material designed to reduce heat transfer with specific thermal resistance properties
Properties
R-Value (EPS)
R-3.6 to R-4.2 per inch
Lowest R-value among rigid foam types, but still effective and economical.
R-Value (XPS)
R-5.0 to R-5.5 per inch
Higher R-value than EPS with better moisture resistance.
R-Value (Polyiso)
R-5.6 to R-7.5 per inch
Highest R-value among common rigid foams, though performance decreases in very cold temperatures.
Compressive Strength
10-100 PSI
Available in various densities for different load-bearing requirements.
Water Absorption (XPS)
0.1-0.3% by volume
Excellent moisture resistance, especially XPS which has closed-cell structure.
Dimensional Stability
High
Maintains shape and size over time with minimal expansion or contraction.
Applications
Exterior Continuous Insulation
Applied over wall sheathing to provide a thermal break that reduces heat transfer through framing members.
Foundation Insulation
Used on the exterior or interior of foundation walls and under slabs to insulate against ground temperatures.
Roof Insulation
Installed above roof decking (in 'warm roof' assemblies) or below decking to increase thermal performance.
Interior Wall Insulation
Applied to the interior side of exterior walls, especially in retrofit applications or where space is limited.
Insulated Sheathing
Used as a combination structural sheathing and insulation layer in some wall systems.
HVAC Duct Insulation
Fabricated into duct insulation for commercial and industrial HVAC systems.
Advantages
- High R-value per inch compared to many other insulation types
- Creates a continuous insulation layer that minimizes thermal bridging
- Excellent moisture resistance, especially XPS and polyiso
- Rigid structure allows for precise cutting and fitting
- Can serve as a vapor barrier at sufficient thickness (XPS and polyiso)
- Durable with long service life
- Relatively easy to install compared to some other insulation systems
- Can add structural rigidity to wall assemblies
Limitations
- Higher cost per R-value compared to fiberglass or cellulose
- Requires protection from UV exposure and physical damage when used externally
- Must be carefully detailed around penetrations to maintain air and water barriers
- Polyiso loses some R-value at very low temperatures
- Most types are flammable and require proper fire protection
- Some types (particularly XPS) use blowing agents with high global warming potential
- Requires mechanical fastening or adhesives for installation
- Joints between boards can create thermal bypasses if not properly sealed
Sustainability Profile
Insulation materials significantly reduce building energy consumption over their lifetime, often offsetting their production impact. Bio-based insulation options offer renewable alternatives to synthetic materials.