Blown in Cellulose Insulation

Cellulose Insulation


With a similar price and few of the problems associated with traditional insulation, cellulose insulation excels in nearly every category. 

It provides far superior real world insulation capacity, resists mold and moisture, repels rodents and pests, reduces sound, slows fires, and noticeably improves comfort in the home. See here for a side by side comparison of common insulation types.

Cellulose insulation is a low cost and high capacity natural fiber that offers better cost-to-performance than all other insulation types in most situations.

It’s made by pulverizing, treating, and fluffing natural fibers. The fibers fray during the process to create countless tiny gaps that traps air. The air struggles to move through these pockets, and the separated trapped air “bubbles” create an excellent insulation barrier.

The modern day version of Cellulose has been used to insulate buildings for over 50 years, though natural fibers have been used for thousands of years. What allowed for cellulose into a common modern day insulation material was the invention of a safe fire resistant treatment. As it slowly gained in popularity over the years, manufacturing costs have dropped markedly to make it increasingly competitive with traditional batt and loose fill fiberglass insulation.


A Real World Example

A developer in Wisconsin built three identical town houses next to each other. The walls and attic of one building had fiberglass batt insulation, another had blown in batts fiberglass (BIB), and the third had cellulose. 
The following winter, total gas and electricity bills for the building insulated with cellulose averaged 40% lower than the fiberglass batts building and nearly 20% lower than the blown-in-batts building. Since heating represents over half of energy usage in Wisconsin, that means cellulose reduced heating costs by up to 80%. It functions similarly well in excessive heat.

R Value of Cellulose

R3.3 per inch, plus more

R Value only tells a fraction of the story, but Cellulose insulation R Value is between 3 and 3.3. Despite having the same R Value as fiberglass, the real world performance of cellulose insulation far exceeds it. This is because the R Value of cellulose improves as it get colder.

Does Cellulose Insulation Contain Asbestos?


There is no asbestos in cellulose insulation–cellulose comes from natural fibers and asbestos comes from mines. In existing attics, however, it is possible for insulation to be layered and mixed. If you are concerned about asbestos, do not touch the insulation and contact an expert.

Is Batt, Roll, or Blown in Insulation Better?

Blowing insulation in attic and wall areas is unquestionably better than batts or rolls. Insulation benefits drop considerably when there isn’t full coverage. For example, having great attic insulation across 1000sq ft but no insulation on the 4sq ft attic hatch will reduce the effective insulation of the attic by 30%. So insulation that naturally has seams has a major disadvantage. 

Are There Cellulose Insulation Moisture Problems?

Not at all–Cellulose has incredible moisture resistant qualities. Some insulation contractors will even install cellulose wet. Once installed, it protects the wood around it by absorbing and safely dissipating moisture.

Benefits of Cellulose Insulation

Improving R Value

R Value Changes With Temperature

While listed at an R Value of between R3 and R3.3 per inch (the same as fiberglass), the value actually increases more the colder it gets (the opposite of fiberglass).

Similarly, as outdoor and attic temperatures increase over 80 degrees, the R Value increases above that listed R3 to R3.3 range.

Air Blocking

and Radiant Barrier

Cellulose insulation is heavier than traditional insulation, allowing it to block air movement. This markedly improves its ability to slow heat transfer. 

The material also blocks radiant heat transfer, so your home will actually feel the temperature on the thermometer.

A Safer Home

Stop Issues Before They Start

Moisture accumulation can lead to major problems like mold and lumber rot. Cellulose insulation not only prevents moisture accumulation, it doesn’t need to be replaced in the event of a leak. 

A natural treatment process also means cellulose resists fire, pests, and rodents.

Where is Cellulose Blown Insulation Used?


Blown in Cellulose Insulation

Most homes must have attic insulation, and blown in cellulose insulation in attic areas is the best approach in the vast majority of situations. If the existing insulation is salvageable, cellulose blown in insulation mixed into fiberglass can improve and extend fiberglass functionality and avoid removal costs. 

Mixing blown in insulation into or over existing insulation will fix gaps and prevent convection loops.

Exterior Walls

Blown in Insulation Walls

Insulation contractors can install cellulose into open walls (no drywall) during renovations and construction. Blown in insulation walls will prevent air from slipping through walls, noticeably dampen sound, block radiant heat, and won’t have seams or gaps. 

Techniques to do insulate walls with cellulose include net and dense packing and damp spraying. Both provide excellent consistency and coverage. 

Existing Walls

Blown in Insulation for Walls with Drywall

Some insulation contractors, including us, can also dense pack cellulose by blowing cellulose insulation into existing walls. By drilling a hole every 1 – 2 feet and blowing insulation into walls, technicians can insulate without removing drywall. 

This process can be done from either side of the wall, so insulating exterior walls from inside or outside the building may be possible depending on siding and wall type.

Basement Walls

Blown in Insulation Walls

Concrete foundation wall insulation is exposed to far more moisture than in other areas of the home, and fiberglass is irrevocably damaged by excess moisture. Since uninsulated basements get too cold in the winter, finished basements tend to be rarely used and are prone to mold. 

Cellulose insulated walls will leave basements comfortable all year round.

Sloped Ceilings

Blown Cellulose Insulation in Ceiling Cavities

Like exterior walls, it’s possible to dense pack cellulose into cathedral ceilings and vaulted ceilings. However, building codes typically require more insulation in roofs than walls, so some of these projects may require closed cell spray foam insulation.

Insulating ceilings without an attic over it often is a difficult yet critical process. Be sure to consult an expert. 

Mold and Sound Control

Extra Rodent Control

Many homes suffer from seasonal mold that stems from low quality or insufficient insulation. Cellulose insulation eliminates surface condensation. Cutoff from water, existing mold dies. Even the resilient mold spores become trapped in the cellulose and eventually die from lack of water.

If being the best value-per-dollar insulation on the market wasn’t enough, cellulose also noticeably dampens sound. Check out our sound control page for more info.

Cellulose Insulation Methods

Batts or Loose Fill?

Loose fill ("Blown") only

Cellulose does not come in batts or rolled insulation form like fiberglass insulation does. Unlike traditional insulation, however, cellulose still works well when packed into confined spaces and isn’t damaged by moisture. These strengths allow for a wider variety of applications.

Blown in Cellulose

in Attics and Open Floors

Dry insulation blown through specialized industrial equipment. This can be a dusty process but is highly efficient. Typically used for attics and filling voids.

Damp Spray Cellulose

in Open Walls

Cellulose dampened with water becomes slightly sticky, enough to build up against surfaces. Scraped flush with studs. Used in open walls, such as in remodels and new construction. Requires drywall to be removed.

Dense Pack Cellulose

in Existing Walls with Drywall

This process also applies to “no-attic ceilings.” Dry cellulose is packed into enclosed cavities until space is filled. Though fewer insulation contractors offer this service, it allows for insulation of existing walls and sloped ceilings without removal of the drywall.

Net and Dense Pack Cellulose

in Open Walls and Ceilings

Large netting gets affixed across open wall or ceiling cavities, then each cavity dense packed with cellulose. Used in open ceilings, walls, and floors. Requires drywall to be removed.


State Rebates & Incentives

Many (though not all) Wisconsin insulation projects are eligible for hundreds of dollars in rebates through the state’s Department of Energy. We typically are able to help at least one client capture a rebate each week.

We are certified to implement these rebates and complete nearly all the paperwork for you. We even instantly discount the rebate from your invoice, so you’re not left waiting for the rebate check to arrive.

Know YOUR Numbers

Planning with general numbers often leads to inaccurate estimations and budgets. That’s one of the many reasons we offer free estimates. Whether you need a quick fix or are planning for work next year, work with actual numbers specific to you.