Choosing the Right Insulation for Your New Home: Fiberglass vs Spray Foam vs Rockwool vs Zip-R Sheathing

Nov 18

Building a new home in Middle Tennessee means balancing comfort, efficiency, indoor air quality, and long-term durability. One of the most important decisions you’ll make during construction is which type of insulation to use. At Leverick Homes, we focus on building healthy, high-performance homes, so selecting the right insulation system is never a one-size-fits-all choice.

Below, I break down the pros and cons of fiberglass, spray foam, Rockwool, and exterior insulation systems like Zip-R Sheathing, and share where each one makes the most sense.

Spray Foam Insulation

Pros

Exceptional air sealing – One of the best air barriers available; dramatically reduces air leakage.
Higher R-value per inch – Great for tight cavities or vaulted ceilings.
Moisture resistance – Closed-cell foam adds structural rigidity and helps control moisture.
Creates a conditioned attic – Keeps mechanicals inside the thermal envelope for better efficiency.

Cons

Higher cost – Typically the most expensive option.
Potential off-gassing during installation – Requires proper ventilation and a reputable installer.
Harder to modify later – Makes future renovations more difficult because it bonds tightly to framing.

Best Use Cases

Conditioned attics, rim joists, vaulted ceilings, areas needing air sealing, high-performance homes.

Fiberglass Batt or Blown-In Insulation

Pros

Cost-effective – Lowest upfront cost.
Easy to install or replace – Straightforward for crews and remodelers.
Non-combustible – Safe and reliable.
Works well in open, ventilated attics – When you’re not conditioning the attic, it’s a simple choice.

Cons

Poor air sealing – Requires additional air-barrier strategies.
Performance varies widely – Must be installed perfectly to hit its advertised R-value.
Can settle or sag – Especially in vertical walls if not installed correctly.
Less moisture resistance – Can absorb moisture and lose performance.

Best Use Cases

Traditional vented attics, budget-sensitive builds, supplemental insulation combined with proper air-sealing.

Rockwool (Mineral Wool) Insulation

Pros

Excellent soundproofing – Great for interior walls or theaters.
Fire-resistant – Withstands extremely high temperatures.
Moisture-resistant – Doesn’t absorb water and maintains insulation value even when wet.
Denser than fiberglass – Provides better thermal performance and a tighter fit.

Cons

No air sealing – Still requires a dedicated air barrier.
More expensive than fiberglass – Mid-range price point.
Heavier – Slightly more labor-intensive to install.

Best Use Cases

Basement walls, interior sound walls, exterior walls when combined with an air-tight sheathing system, high-humidity areas.

Exterior Insulation Panels: Zip-R Sheathing & Rigid Foam

Exterior continuous insulation is one of the most effective ways to improve a home’s energy efficiency and durability.

Pros

Continuous thermal barrier – Eliminates thermal bridging through studs.
Better moisture management – Zip-R sheathing integrates a WRB (weather barrier) with exterior R-value.
Increases whole-wall R-value – Outperforms interior cavity insulation alone.
Improves comfort – Reduces hot and cold spots throughout the home.
Excellent for building science-driven construction – A key component in “healthy luxury” homes.

Cons

Higher material cost – More expensive than standard OSB sheathing.
Requires careful detailing – Taping, flashing, and transitions must be done correctly to prevent moisture issues.
Not a replacement for cavity insulation – It supplements but doesn’t replace fiberglass, rockwool, or spray foam inside walls.

Best Use Cases

High-end custom homes, energy-efficient builds, homes needing superior moisture and temperature control.

Which Insulation Is Best for Your Home?

Each product has a role:

Best for all-around performance: Spray foam + Zip-R exterior insulation
Best budget choice: Fiberglass with a dedicated air-seal package
Best sound & fire resistance: Rockwool
Best building-science approach: Zip-R plus Rockwool in the cavities

At Leverick Homes, we typically blend materials to deliver maximum performance without unnecessary cost. For example, we might use:

Spray foam at the roof deck for a conditioned attic
Rockwool in exterior walls for fire resistance and density
ZIP-R or a rainscreen system for moisture control
Fiberglass in select areas where it makes sense

This hybrid approach creates a more comfortable, durable, and energy-efficient home that stands out from typical construction in Middle Tennessee.

Final Thoughts

The right insulation strategy depends on your home’s design, your budget, and the performance level you want. If you're building in middle Tennessee, choosing the right insulation system has a huge impact on comfort and long-term value.