Blow-in cellulose insulation is one of the most popular types of insulation used in homes today. Made from recycled newspaper, cardboard, and other paper products, cellulose insulation offers a number of advantages over traditional fiberglass batt insulation. Here is everything you need to know about blow-in cellulose, from how it works to how it compares.
What is Blow-In Cellulose Insulation?
Blow-in cellulose insulation, also known as loose-fill insulation, refers to paper-based insulation material that is blown into wall cavities, attics, and other spaces using special pneumatic equipment. The cellulose fibers form a thick, fluffy insulation blanket that fills cracks and crevices, creating an effective air seal.
Unlike rigid fiberglass batts, blow-in cellulose is loose, allowing it to flow easily into spaces. The insulation is treated with fire retardant chemicals and sometimes mixed with a very small amount of binder fibers to help it stay in place. This flexibility makes it ideal for retrofitting insulation into existing homes.
How Does Blow-In Cellulose Insulation Work?
Blow-in cellulose insulation creates a thick insulation layer that traps air and reduces heat transfer in a home. The millions of tiny cellulose fibers slow the movement of heat, either from hot interior air escaping in the winter or hot exterior air entering in the summer.
The loose-fill application allows it to fill building cavities of any shape or size, eliminating gaps and settling that can compromise insulation performance. Cellulose is highly resistant to air infiltration, creating a strong air barrier that improves energy efficiency.
The insulation is treated with borates or other fire retardant chemicals that help cellulose resist fire. Cellulose insulation contains about 85-90% recycled paper fiber, along with fire retardants and sometimes a very small amount of binder material.
Key Benefits of Cellulose Insulation
- Excellent insulating value – Cellulose insulation offers an R-value between R-3.2 to R-3.8 per inch. This makes it one of the best insulating values among common insulation materials.
- Air infiltration resistance – Cellulose is very dense and expands to completely fill spaces. This resists airflow through cracks, reducing drafts.
- Recycles waste paper – Over 85% of cellulose insulation is made from recycled paper waste. Using it reduces strain on landfills.
- Cost-effective – Cellulose insulation is competitively priced with fiberglass insulation. And better air sealing can lead to energy savings that offset the cost.
- Flexible application – Loose-fill cellulose can reach spaces that standard batt insulation cannot, like irregularly shaped cavities.
- Less settling – Cellulose insulation is good at staying in place once installed and resists settling that leads to thin spots.
- Minimal VOC emissions – Unlike some types of insulation, cellulose insulation emits very low VOCs after installation.
How Does Cellulose Compare to Fiberglass Insulation?
Fiberglass insulation has long been one of the most common types of home insulation. But cellulose has gained popularity as an efficient and eco-friendly alternative. Here are some key differences between fiberglass and cellulose insulation:
- Insulating value – Cellulose has a slightly higher R-value per inch (R-3.8) than most fiberglass (R-3.0 to R-3.5).
- Air infiltration – Cellulose is much denser than fiberglass, blocking drafts and filling cavities better.
- Recycled materials – Cellulose contains 85%+ recycled content versus 30-40% for most fiberglass.
- Application – Loose-fill cellulose can reach more spaces than inflexible batt fiberglass.
- Cost – Cellulose is competitively priced with fiberglass insulation.
- Off-gassing – Cellulose emits minimal VOCs compared to some fiberglass products.
- Settling – Low-quality fiberglass is prone to settling over time, creating thin spots. Cellulose resists settling better.
So while fiberglass continues to be a popular option, cellulose offers excellent thermal performance along with environmental benefits. Many homeowners are making the switch to take advantage of these features.
What Are the Drawbacks of Cellulose Insulation?
Cellulose insulation offers many benefits, but there are a few potential downsides:
- Moisture sensitivity – Like most natural fibers, cellulose insulation can lose some R-value if it gets wet or absorbs moisture. Proper moisture barriers are important.
- Pests – Paper insulation provides nutrients that can attract pests like mice. But fire retardant treatments make it less appetizing.
- Compressed R-value – When compressed, cellulose’s insulation value drops a bit more than fiberglass. Proper installation density helps address this.
- Dust – Loose particle insulation releases some dust during application, requiring masks and proper site cleanup.
- Professional installation – For best results, most homeowners rely on professional installation, rather than doing it themselves.
With proper selection, good moisture barriers, and quality installation, these drawbacks can be minimized. And cellulose still offers excellent insulation capacity for the majority of modern homes.
How Much Does Blow-In Cellulose Insulation Cost?
On average, cellulose insulation costs $1.00 to $1.50 per square foot installed. However, the price can vary depending on your location and specific project details. Some key factors impacting cellulose insulation cost include:
- Accessibility – Insulating very tight spaces or working around obstructions will increase labor time and cost.
- Existing insulation – Adding cellulose over old insulation will typically cost less than installing it into empty cavities.
- Insulation amount – More insulation thickness to achieve higher R-values raises materials costs.
- Labor – If you hire a professional installer, labor will account for about 50% of the total cost. DIY installation saves significantly on labor.
- Location – Insulation pricing is very regional, with lower costs in rural areas typically.
For reference, you might spend $1,200 to insulate an average 1500 square foot attic to R-49 with a professional installer. Get free estimates to find exact costs for your specific project.
What Are the R-Values for Blow-In Cellulose?
The R-value refers to an insulation’s capacity to resist heat flow. The higher the R-value, the better the insulation performance. Cellulose insulation offers R-values between R-3.2 to R-3.8 per inch.
This can vary slightly based on factors like installation density, but a typical R-value for cellulose insulation is about R-3.7 per inch.
Some common R-values for various insulation thicknesses:
- 5 inches – R-13 to R-19
- 6 inches – R-19 to R-22
- 8 inches – R-25 to R-30
- 10 inches – R-32 to R- 38
- 12 inches – R-38 to R-46
Ideally, you should install cellulose insulation to match or exceed the recommended R-value for your climate zone. Adding more thickness increases the R-value and insulation capability.
How Thick Should Blow-In Cellulose Insulation Be?
Recommended cellulose insulation thicknesses vary based on your attic, floors, walls, and climate:
Attics: Most attics should have at least R-49 insulation value. This usually requires blowing 12″ to 15″ of cellulose insulation over the existing attic floor. Warmer climates may only need 10″ to achieve R-38.
Cavity Walls: Walls should have R-13 to R-15 in colder climates and R-11 in warmer zones. This typically requires a blow-in cellulose insulation depth around 3.5” to 5.5” in stud wall cavities.
Floors: Insulate between floor joists to R-30 or thicker. This usually requires 10″ to 12″ depth of insulation.
The best way to determine target insulation thickness is to have an energy audit done for your home. The auditor tests insulation levels, air leakage, and other factors. They can advise the ideal R-value and insulation depth for your climate.
Does Blow-In Cellulose Insulation Settle?
All loose-fill insulation is prone to some settling over time as the materials compress under their own weight. However, cellulose experiences very minimal settlement compared to other insulations like fiberglass.
Cellulose is dense and installed at optimal densities of around 3.5 to 4 pounds per cubic foot. At this consistency, cellulose locks tightly into place in cavities. It resists movement or compression much better than loose, fluffy fiberglass.
Low-quality fiberglass insulation can settle quite severely, losing up to 50% or more of its thickness over time. Higher density “stabilized” fiberglass resists settling better but is still more prone to it than cellulose.
With proper installation, cellulose insulation typically settles less than 2% over many years. Regularly inspecting attic insulation and adding insulation if needed helps ensure continued energy efficiency.
Does Cellulose Insulation Get Moldy or Rot?
Cellulose insulation is made from paper and other wood-based fibers, which are vulnerable to mold growth and rot when exposed to moisture. However, cellulose insulation contains borates and other fire and pest-resistant chemicals that also prevent mold and rot.
As long as the cellulose stays dry and out of standing water, it will not decay or develop mold growth. Like all insulation, proper waterproofing and vapor barriers are critical when installing cellulose to keep it protected.
If installed correctly in a properly air sealed and ventilated space, cellulose insulation will not sustain mold growth any more than fiberglass insulation. Getting bulk water or moisture intrusion under control is also key to preventing mold.
Overall, mold susceptibility should not be a major concern regarding cellulose insulation. With good installation and water management, it will last for decades.
Does Cellulose Insulation Attract Mice or Bugs?
Untreated cellulose insulation contains lots of fiber that could potentially attract pests who want to nest in it. However, modern cellulose insulations use borate treatments that resist insects, rodents, and other pests.
Borates act as a stomach poison to deter pests from trying to eat the paper fibers. Fiberglass insulation uses similar chemicals to resist pest damage. Professional chemical treatments also help repel termites.
While not completely pest proof, properly treated cellulose insulation is no more vulnerable to bugs, beetles, mice, etc. than fiberglass or other insulations. Care should be taken around eaves and attic access points to seal off any entry points rodents could use.
Will Blown-In Cellulose Insulation Irritate My Skin or Lungs?
Loose cellulose insulation fibers and particles can cause eye, skin, and respiratory irritation during handling and installation. Temporary irritation and itching is common. To avoid problems:
- Wear long sleeves, gloves, eye protection, and N95 masks when installing or working around cellulose insulation.
- Limit exposure time and take frequent breaks to reduce irritation.
- Use vent fans and open windows when appropriate to keep air circulating.
- Wash exposed skin gently with soap and water after contact.
- Rinse eyes thoroughly if particles get in them.
- Avoid spreading loose cellulose fibers outside the work area.
- Change clothes after installation to avoid spreading fibers.
The dust and fibers primarily cause mechanical irritation rather than allergic reactions. So symptoms should subside within a day or so after exposure ends. Use caution when working directly with loose cellulose to minimize discomfort.
Is it Hard to Install Blow-In Cellulose Insulation?
Installing loose-fill cellulose insulation takes some work, but it is very manageable as a DIY project for many homeowners. The basic steps include:
- Clear attic, roof vents, utilities, etc. to access installation areas easily.
- Set up insulation blowing machine and run hoses to attic.
- Wear protective gear like dust masks, goggles, and gloves.
- Blow insulation into open cavities in walls, roof, and floors to desired depth.
- Level and smooth insulation layer, being careful around soffits and vents.
- Seal attic access points carefully with baffles to contain insulation.
- Clean up dust and fibers thoroughly afterwards.
Going slowly and carefully makes the installation process easier. Blowing machines are available at home centers to rent. Having an extra person to help out is also useful.
Hiring a professional insulation installer makes the process fast and easy but adds to the cost. They have the right equipment and experience to do it efficiently. Either way, take steps to properly protect yourself from dust exposure. With attention to detail, cellulose can be installed by an average DIYer willing to put in some work.
How Long Does Blow-In Cellulose Insulation Last?
Cellulose has been used for residential insulation for over 80 years. When installed properly in dry, protected areas, cellulose insulation lasts for many decades.
The borates and other chemicals protect the wood fibers from damage while resisting mold, fungi, insects, and rodents. Over time, some settling occurs, reducing thickness slightly.
Homeowners should inspect attic insulation periodically and add cellulose if needed to maintain the ideal R-value. As long as cellulose remains dry and undamaged, it does not deteriorate quickly and continues providing excellent thermal insulation.
Proper maintenance and avoiding moisture issues can help cellulose insulation remain effective at reducing energy costs for the lifetime of the home. Its longevity and performance make cellulose a great investment.
Can You Add More Cellulose Insulation Over Existing Fiberglass?
It is perfectly fine to blow cellulose insulation over top of existing fiberglass batts or rolls. This is a common way to increase attic insulation levels without removing the current insulation.
Fiberglass batts provide a nice flat surface for the blown cellulose to build up on. The combination creates a very thick insulation layer with excellent thermal resistance and sound dampening.
Before blowing over fiberglass:
- Inspect and repair any attic air leaks or moisture issues.
- Install baffles to provide proper attic ventilation.
- Carefully work cellulose around ducting, wiring, and other obstructions.
- Level the finished cellulose layer to target depth for best insulation consistency.
- Make sure soffit vents remain clear to prevent moisture buildup.
Blowing cellulose over fiberglass allows you to very cost-effectively improve energy efficiency. This retrofit approach prevents waste by keeping the existing usable insulation in place.
Does Cellulose Insulation Keep Sound Out?
In addition to insulating against heat transfer, cellulose also dampens sound transmission very effectively. The dense packed fibers absorb noise and vibrations better than air spaces or less dense insulations like fiberglass.
Tests show cellulose insulation can achieve Sound Transmission Class (STC) ratings above 40, which indicates good sound blocking capacity. The more thickness added, the higher the STC rating and noise control.
Key benefits of cellulose for sound control:
- Absorbs noise before it enters walls and ceilings.
- Muffles vibrations that transmit sound through structures.
- Reduces echoes and resonances within rooms.
- Can be blown into cavity areas around noise sources for extra sound dampening.
- Is very affordable way to upgrade soundproofing.
For better acoustical separation between living spaces, blown-in cellulose is an excellent option compared to just drywall or fiberglass alone. The noise reduction increases comfort and privacy.
Is Cellulose Insulation Safe? Fire and Health Concerns
With proper installation, cellulose insulation does not present any significant health or fire risks. The safety concerns around cellulose include:
Fire Safety: Cellulose is treated with chemical fire retardants to meet building code safety standards. This prevents it from being a fire hazard.
Dust: Cellulose dust can cause minor throat and eye irritation. But masks minimize exposure during installation.
Pests: Chemical treatments deter insects and rodents from nesting. Sealing entry points adds further protection.
VOCs: Unlike some insulation, cellulose emits very minimal volatile organic compounds (VOCs) that can decrease indoor air quality.
Moisture: Cellulose should not get continually wet. Vapor barriers and ventilation prevent moisture issues.
Weight: Dense packed cellulose is very heavy and requires attic structures to support the load.
As with any building material, basic safety practices like wearingmasks are advised when installing cellulose. Overall, when installed correctly in dry conditions, cellulose insulation is considered a very safe product for your home.
Key Takeaways on Blow-In Cellulose Insulation:
- Cellulose insulation contains 85% recycled paper fiber and offers impressive R-3.5 per inch.
- The loose material fills cavities thoroughly and resists settling.
- Cellulose insulation provides excellent air sealing and sound dampening.
- Borates protect cellulose from fire, pests, mold, and rot when kept dry.
- Wearing PPE minimizes dust and fiber exposure during installation.
- Adding cellulose over existing batts is an effective way to improve energy efficiency.
- With reasonable DIY effort, cellulose insulation offers an affordable way to gain more comfort, energy savings, and soundproofing.
Frequently Asked Questions
How long does blow-in cellulose insulation installation take?
The time required to install cellulose insulation depends on factors like the square footage to be insulated, number of installers, and desired R-value. For a typical 1500 square foot attic with an R-49 target, professional installation usually takes 6-8 hours. DIY installation may take 15-20 hours.
Does cellulose insulation have to be covered?
Covering or encapsulating cellulose is not required, though many pros recommend installing Kraft faced fiberglass batts over top for additional air sealing and to hold it in place. Some local codes may require covering exposed cellulose in occupied spaces.
What thickness of cellulose insulation is best?
Recommended