Rigid Board
Polyisocyanurate (Polyiso) Insulation
Complete guide to polyisocyanurate (polyiso) insulation: R-value, installed cost, pros, cons, and best applications.
Key Specifications
5.6–8
R-Value per Inch
$0.80–$1.50
Material Cost/sqft
$1.50–$2.80
Installed Cost/sqft
9"
Depth for R-60
Cost Analysis (1,200 sq ft Attic)
| Option | Low Estimate | High Estimate |
|---|---|---|
| Material only (DIY) | $960 | $1,800 |
| Professionally installed | $1,800 | $3,360 |
*Estimates for a full install to Climate Zone 5 R-60 depth. Use the calculator for your specific situation.
+ Pros
- ✓Highest R-value per inch of any rigid board (5.6–8.0)
- ✓Thin profile for space-constrained applications
- ✓Low global warming potential compared to XPS
- ✓Widely used in commercial roofing
− Cons
- ✗R-value decreases significantly in cold temperatures
- ✗More expensive than EPS or XPS
- ✗Facers required — core is fragile without them
- ✗Not suitable for below-grade applications
Best Applications
- →Compact assemblies where every inch of depth counts
- →Low-slope commercial roof deck insulation
- →Above-deck applications in mild to warm climates
Comparing Insulation Types
Polyisocyanurate (Polyiso) is a rigid board insulation. With R-5.6–8 per inch, it offers among the highest R-values per inch available, ideal for space-constrained applications.
View full insulation type comparison →Explore Other Insulation Types
Is Polyisocyanurate (Polyiso) Right for Your Attic?
Use our free calculator to get a personalized recommendation based on your climate zone, attic size, and budget.
Calculate My Insulation Needs