What are the main differences among fiberglass batts, mineral wool boards, and cellulose loose-fill in terms of installation and performance?

• A. All three materials perform identically in installation ease and moisture handling.
• B. Fiberglass batts must be sprayed; mineral wool boards are poor in exterior assemblies; cellulose cannot be recycled.
• C. Cellulose is recycled and dense, but requires proper installation to avoid settling.
• D. Batts install quickly in standard bays but can gap; loose-fill fills irregular cavities and provides tight overall fit; mineral wool boards provide high fire resistance and compressive strength and can be used in exterior assemblies; cellulose is recycled and dense, but requires proper installation to avoid settling.

Answer: (D)

The main idea here is how the form and composition of each insulation type shape both how you install it and how it performs in the space.

Fiberglass batts fit into standard framing bays and go in quickly, but they can create gaps if they’re not cut and fitted precisely around obstacles or when framing isn’t perfectly square. That gap reduces the thermal performance, so careful fitting matters even though installation is fast.

Mineral wool boards are rigid, dense panels. They’re installed as solid layers that resist compression and fire well, which makes them especially suitable for exterior assemblies where you want durability and a continuous, weather-ready layer. Their rigidity helps maintain a continuous barrier without the same risk of sagging or gaps that batts can have.

Cellulose loose-fill is blown in to fill irregular cavities. Its recycled content is a plus, and when properly dense, it can achieve a tight overall fill that minimizes air gaps. However, it can settle over time if not installed at the correct density, which is why proper installation is crucial to maintain performance.

That combination of installation method and performance characteristics is what makes the described option the best fit.