If you have ever peered into the hatch of an older Des Moines attic, you likely saw strips of "Pink Fluffy" insulation unrolled between the wooden floor joists. Today, if you hire an elite energy contractor to upgrade that exact same attic to an R-60 rating, they almost certainly will not use rolls. Instead, they will use massive hoses to "blow in" loose, shredded material. What caused this entire industry shift away from rolled batts in attics?

The Mechanics of Rolled (Batt) Insulation

Rolled insulation, typically made of fiberglass or mineral wool, comes in pre-cut widths (usually 15" or 23") designed to friction-fit perfectly between standard wall studs or attic joists.

Where It Thrives: Rolled batts are fantastic for new construction walls. Before the drywall goes up, an installer can quickly and perfectly place the batts into wide-open, uniform rectangular spaces.

Where It Fails (The Attic): An attic floor is rarely a set of perfect rectangles. It is chaotic. It is full of cross-bracing, diagonal roof trusses, electrical wires, bathroom vent pipes, and recessed light housings. Trying to perfectly cut a fiberglass batt to fit securely around forty low-voltage wires and pipes is nearly impossible. If you simply drape the batt over the wires, it creates massive "air pockets" underneath. Physics dictates that any air pocket destroys the R-Value of the insulation system.

The Mechanics of Blown-In Insulation

Blown-in insulation (either cellulose or loose-fill fiberglass) is pumped through a 4-inch hose attached to an industrial blowing machine outside the home.

The Fluid Advantage: Because the material is loose and blown at high velocity, it acts like a fluid. It wraps seamlessly around every single wire, pipe, and truss plate in the attic. It fills every crack and crevice, creating a continuous, seamless "blanket" on the attic floor. There are zero gaps, zero air pockets, and zero seams for heat to escape through.

Burying the Thermal Bridge

Perhaps the greatest advantage of blown-in material in a cold climate like Iowa is its ability to combat "thermal bridging." Wood is a terrible insulator. If you just lay rolled batts between your 2x6 attic floor joists, the tops of those wooden joists are still exposed to the freezing attic air, conducting heat straight out of your home.

To reach a true R-60 rating, a contractor will use the blowing machine to bury the entire floor structure under 16 to 18 inches of material, completely covering the tops of the joists and stopping the thermal bridging dead in its tracks.

The Verdict for Iowa Homes

For open walls during new construction or a basement remodel, Rolled Batts are still a cost-effective and highly viable option (assuming they are installed perfectly). However, for insulating a pre-existing attic, Blown-In Insulation is vastly superior. It yields better coverage, eliminates air pockets, covers thermal bridges, and can be easily pumped right over the top of existing, substandard fiberglass batts.