Not all insulation is created equal—and not every type is suited for exterior application. Here’s a breakdown of the most common exterior insulation types and where each performs best.
1. Rigid Foam Board (EPS, XPS, Polyiso)
Expanded Polystyrene (EPS): Affordable, good R-value per inch, water-resistant
Extruded Polystyrene (XPS): Higher compressive strength, smooth finish, more moisture resistant
Polyisocyanurate (Polyiso): Highest R-value per inch but performance drops in very cold climates
Best For: Residential and commercial wall assemblies, under cladding, behind rain-screens
2. Mineral Wool (Rockwool)
Fire-resistant, breathable, water-repellent
Excellent acoustic and thermal performance
Slightly heavier and more expensive than foam
Best For: High-performance walls, fire-rated assemblies, and noise-sensitive areas
3. Wood Fibre Boards
Eco-friendly and vapor-open
Great for Passive House or natural building designs
Needs extra detailing to protect against moisture
Best For: Net-zero or sustainable builds focused on low embodied carbon
Accent Exteriors selects insulation systems based on climate zone, wall composition, budget, and energy goals—ensuring each layer of the envelope performs.
Did you find this article helpful but still have questions?
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