Blown-In Insulation: Better Than Rolling Out Fiberglass?

Blowing In Attic Insulation 183768691
Blowing In Attic Insulation. Getty / Banks Photos

Blown-in insulation might be just the energy solution you need for those chilly fall and winter days.  

Have you ever hauled fiberglass batts or rolls through a small attic door and laid them out between uncooperative ceiling joists?  Then you might look longingly towards blown-in cellulose insulation as an easier and possibly more energy efficient solution.

Just how does blown in insulation work and is it any better than fiberglass rolls or batts?

Blown In Insulation Defined

Loose-fill insulation is blown into both attics (above the ceiling) and into walls by means of an electric blower.

With walls, blown-in is the only kind of insulation you can use--short of pulling down interior drywall, installing rolled fiberglass insulation, then re-installing the drywall.  With ceilings, though, blown-in is optional, a choice between that and long fiberglass batts that you lay down.

Cellulose insulation is made from post-consumer recycled paper derived from telephone books, tax forms, and newspapers are some of the paper products that are used to make cellulose insulation.  The paper receives a boric acid treatment, which renders the paper relatively resistant to fire.  But it is not completely fireproof.

 Blown-InFiberglass Roll or Batt
DefinedLoose cellulose insulation sprayed with a blower.Fiberglass mats that come in rolls or long strips called batts.
Best for DIYHomeowners can rent blowers, though project is best left to professionals.Best.  Physically arduous job, but no special tools are required.  
Which Is Warmer?R-value of loose fill cellulose is R-3.2 to 3.8 per inch.R-value is 3.7 per inch based on R-13 insulation.
CostComparable for materials, though blower rental may drive the entire project cost higher than that of fiberglass insulation.Comparable, though labor costs may be increased for attics with an unusually large number of obstructions.
Walls or Ceiling?Both.  However, homeowners should not attempt wall blown-in insulation.Both.  But if the walls are already closed up, it usually makes more sense to use blown-in insulation than to open up the walls in order to install fiberglass.

How Blown-In Is Done:  Walls and Attics


With existing, closed-up walls, blown-in is the highly preferred way to go--unless you want to rip off exterior siding or interior drywall to access wall cavities.  

When doing a major remodel that involves replacing drywall, this is a perfect opportunity to insulate with fiberglass rolls.


Blown-in is an imperfect process. It is almost too much to expect cellulose fibers to pass through a two-inch diameter hole and settle uniformly throughout a wall cavity. Especially in older homes, wall obstructions abound: electrical wires, plaster "keys", fire blocks, etc.

Knowing where obstructions are located is almost an intuitive process. Most insulation technicians are experienced at probing for blocking and wires, and know how to devise workarounds. 

  1. Making Holes:  The technicians drill holes: one hole about 12" from the ceiling, another hole about 3 feet from the floor. Since most studs lay 16" on-center from each other, you can expect these holes to be about every sixteen inches.
  2. Blowing:  Using an insulation blower, a technician forces cellulose or mineral fiber loose insulation into your walls.
  3. Patching:  Walls are plugged with plastic plugs.  Will the contractor paint the plugs? Most likely not, since insulation techs are not painters. However, as long as you have paint on hand, it is a relatively easy job to dab paint on those sections.


With attics, blown-in is the preferred way to go if you want to use eco-friendly products, as it is made from recycled paper products.


Blowing in insulation is not as simple as standing at the attic access door and expecting to cover the entire attic; it entails moving around the attic almost as much as if as if you were rolling out batts.  

Blown-in insulation settles easily around attic obstructions.  

One plus for fiberglass batts has nothing to do with energy savings or ease of installation.  If you need to work on anything in the attic later on, it is far easier to pull back fiberglass batts than to scoop away loose-fill cellulose.

The Mold Factor

When when blown-in attic cellulose gets wet, it takes a long time to dry out--if ever.  After cellulose gets moldy, it is a long, arduous project to scoop it out into plastic contractor's bags and haul it down, bag by bag.

When attic fiberglass batts or rolls get moldy, it is relatively easy to roll up and throw away the entire batt or cut out the affected portion.

The Fire Factor

Even though cellulose blown-in insulation is relative fireproof, it can have a long-term smoldering effect when subjected to high heat or fire.  This can be a concern in attics, where high temperature recessed lights may be.

In walls, blown-in insulation has been proven in studies to improve walls' fire resistance over no insulation at all.