Cellulose Insulation or Fiberglass Insulation?
Which is better for your Attic?

Insulating Your Attic

Insulation is a necessity for any home. It provides warmth in the winter and cools in the summer. However, not all insulation materials act the same. Each type of insulation has its benefits and disadvantages. This article will explore the differences to determine which is better for your Attic – cellulose insulation or fiberglass insulation.
Adding insulation to a home attic provides the following benefits:
  • Lowers energy bill
  • Increased comfort for the home’s occupants
  • Reduced greenhouse gas (GHG) emissions
  • Durable
  • Reduces drafts
  • It keeps homes more relaxed in the summer and warmer in the winter
  • Long-lasting
  • Affordable
  • Easy to install when carried out by a qualified insulation contractor
Insulating Your Attic

Cellulose Insulation or Fiberglass Insulation


When exploring the different types of insulation, you’ll find that the most common forms are fiberglass or cellulose. Without a doubt, fiberglass remains the most common and traditional choice, but cellulose insulation is a rising contender. With so many homeowners focusing on eco-friendly and sustainable insulation choices, cellulose is overtaking fiberglass in popularity in some county regions.

Insulating Attic Space


You might be surprised to learn that many older homes lack insulation in the Attic and floor. Bare, uninsulated areas of your home let heat and cooling escape, increasing your home’s energy consumption substantially. Promptly insulating such areas with either fiberglass or cellulose will reduce your monthly costs and make the home’s entire interior space feel more pleasant with fewer drafts.

Insulating your Attic is a necessity to prevent heat from escaping through your ceiling and roof. If your Attic already has insulation, then you can use a ruler to measure the insulation’s depth to determine your R-value. The Department of Energy’s Insulation Fact Sheet is a great guide to help you determine if you need to add insulation to the attic space. You can also contact an insulation contractor for a free consultation.

Environmental Considerations of Insulation


Worldwide, many people have started to focus on environmental concerns as climate change causes widespread havoc. To become eco-friendly, homeowners are actively seeking out sustainable choices.

Cellulose is manufactured from recycled newspapers. Although, the material does contain chemicals such as chemical fire retardants and insect repellants.

Fiberglass is made of glass and sand. The glass is a natural resource, and some of the glass is obtained from recycled glass. In a recent U.S.government study, it was found that most US fiberglass manufactures make their insulation from 20 percent recycled glass.

Both fiberglass and cellulose insulation have eco-friendly perks. Overall, cellulose is probably made of more recycled material, but fiberglass is also manufactured using environmentally friendly materials.

R-Value of Cellulose vs. Fiberglass Insulation


Take a piece of cellulose insulation and a similar-sized piece of fiberglass insulation. You’ll probably be surprised to learn that cellulose has a higher R-value than fiberglass.

R-Value is very important when considering insulation choices. It is the measurement that shows the insulation’s ability to block the movement of heat effectively. A high R-value has much greater insulative factors. Basically, the higher the R-value number, the better the performance.

  • Loose-fill cellulose insulation has an R-value of 3.2 to 3.8 per square inch.
  • Loose-fill fiberglass has an R-value of 2.2 to 2.7 per square inch.
  • Cellulose offers a greater R-value.

Code Limits on Insulation


The majority of California is considered a Zone 3 according to the International Energy Conservation Code and the California Energy Commission, which requires an attic insulation R-value of between 30 to 60. Although new construction homes meet the requirements, very few older homes have sufficient insulation.

To achieve the code limits, you’ll need to have new insulation added on top of the old insulation. If you have fiberglass insulation in your Attic that is rated at R-13, then you’ll need to add another 10 inches of insulation to achieve the state’s required R-value. You can add less cellulose to achieve the R-value. When figuring out which type to use, fiberglass or cellulose, you’ll want to determine the costs with your insulation contractor. Often the cost of one varies dramatically from the cost of the other.

Air Leakage and Insulation


Neither fiberglass nor cellulose insulation acts as an air barrier. Both allow air circulation. Air circulation is a part of the effectiveness of insulation and helps promote its insulative properties. The air becomes trapped in the insulation and further helps insulate the structure.

Cellulose can slow down airflow within walls which might make it less than an ideal choice for such a location when compared to fiberglass insulation. However, it is adequate attic insulation.

If fiberglass batts should become compressed, then they can lose their air pockets and insulative effectiveness.

Extreme Temperatures: Cellulose vs. Fiberglass Insulation


Both cellulose and fiberglass insulation work well with moderate temperature fluctuations, but they differ dramatically if the mercury drops. When the outdoor temperature falls below freezing (around 20 degrees Fahrenheit), the fiberglass starts to lose up to 50 percent of its R-value. It loses efficiency due to its inability to create an air pocket as a result of a breakdown.

Unlike fiberglass, cellulose does not break down or lose its R-value in the extreme cold, making it the favored choice in areas of the state, such as Northern California, where the temperature can become freezing.

How Much Is Insulation Too Much?


You might think that adding more insulation is better, but that is not always the case. Most insulation contractors will agree that exceeding the recommended R-Value for the region offers little or no additional benefits.

Where to Insulate in Your Home


Are you wondering where in your home you should add insulation? Here is a list of areas that you might want to consider adding insulation:

  • Insulate the home’s Attic, crawl space, and outer walls because heat can quickly transfer through such voids.
  • Add additional insulation around water heaters to prevent heat loss. You can also purchase pre-cut insulation jackets or blankets with an R-value of 8 to place around the water heater and reduce heat loss up to 45 percent. Estimates vary, but most agree that it will preen heat loss by about four to nine percent.
  • Wrap all hot water pipes using tubular insulation to protect from freezing and help keep the water warm The insulation will increase the water’s temperature by two to four degrees Fahrenheit
  • Apply insulation around all air and heating vent ducts to ensure proper and efficient operation, plus reduce possible vibration which can cause noise. Insulating ducts in the Attic, crawl space, unfinished basements, and garages will improve the structure’s energy efficiency.

Fiberglass Insulation


You are probably familiar with pink fiberglass insulation (sometimes yellow). It is a cloud-like material, and the pink version looks like cotton candy. Undoubtedly, fiberglass is the most common kind of insulation. It is low-cost and highly effective at regulating your home’s temperature.

Fiberglass insulation is made from recycled glass material that is melted and mixed with a substrate like a limestone or sand. It is then woven into very fine, long strands.

There are many forms of fiberglass insulation, such as the following: batts and loose-fill.

» Batts of Fiberglass

Batts are rolled-up sheets of spun fiberglass that are packed using either adhesive paper or aluminum foil. This form of fiberglass insulation is prevalent because it is quick and easy to use. The insulation can easily be laid between joists in a home. You simply unroll the batts and attach them.

Unfortunately, fiberglass batts are hard to customize, so you might have difficulty installing the insulation around pipes and other obstructions that commonly occur in joists. Luckily, if you have hard to insulate areas, then you can opt to use loose-fill fiberglass.

» Loose-Fill Fiberglass

Loose-fill fiberglass is made from the same glass fibers as batts. Unlike batts, it is not woven into long blankets of fiberglass. Instead, the insulation is cut down into smaller pieces. The pieces are blown in position within an attic or walls using an insulation blowing machine.

The use of loose-fill fiberglass insulation is favored for locations where you cannot easily install batts.

» Pros and Cons of Fiberglass Insulation

All forms of insulation have pros and cons. Fiberglass is a popular choice due to its many advantages.

Pros of Fiberglass Insulation:
  • Cost-Effective: Fiberglass insulation is relatively low-cost to purchase and install.
  • Energy savings: Installing the insulation can reduce your energy bill.
  • Moisture resistant and Non-flammable: Made up primarily of glass, fiberglass is fire resistant and resists moisture well, making it a popular choice for use in areas with high humidity, such as coastal regions of California.
  • Long-lasting: Fiberglass insulation will easily last up to 100 years.
  • Noise Insulative: Fiberglass acts as an effective insulator that not only shields your home from heat and cold extremes but also against unwanted noise penetration.
Cons of Fiberglass Insulations:
  • Ineffective When Moist: When fiberglass insulation becomes wet (such as a roof leak), it becomes ineffective and must be professionally dried to return its insulative efficiency.
  • DIY Problems: Self-installation of fiberglass insulation is strongly discouraged because it is made from tiny glass fragments that are dangerous when handled. Handling fiberglass insulation with bare skin can lead to rashes. Also, if you accidentally inhale the fiberglass insulation, then you can sustain lung damage. Ideally, all fiberglass insulation should be installed by a professional insulation contractor.
  • Health Risks: In 1994, fiberglass becomes classified as a potential carcinogen but was still considered not a significant health hazard in homes. To be dangerous, the fiberglass fibers must become airborne, and if left undisturbed, the fiberglass insulation poses no health dangers. An insulation contract will use a proper mask for protection and seal the inside of walls, so the fiberglass poses no dangers to the home inhabitants.

Cellulose Insulation


Cellulose insulation is formed from about 85 percent recycled material such as paper or tiny pieces of wood. The fibers are shredded and further fiberized, which are then packed tightly together to hold in the heat.

Installation of cellulose requires the removal of siding on the home’s walls. An insulation contractor will then drill several holes drilled into the wall of the structure. The cellulose is then blown within the wall cavities and attic space.

It is installed with either a damp spray technique or dry netting when installing cellulose into new construction.

  • Damp sprayed: Moisture is added to the spray nozzle of the insulation applicator. The moisture activates the start found in the cellulose. The insulation can then be sprayed into the home’s cavities.
  • Dry netting: A net is filled with cellulose insulation and then placed over the openings of the building.

The most effective insulation installation depends on your personal preference and what tools you have available.

» Pros and Cons of Cellulose Insulation

There are many advantages to using cellulose insulation and some disadvantages. When trying to determine whether to choose cellulose, you’ll want to weigh the pros and cons.

Pros of cellulose insulation include:
  • Affordable: Cellulose insulation is fashioned from recycled paper, which marks it as highly affordable. In most cases, it costs about 75 percent less than fiberglass.
  • Easy to install: The small and lightweight pieces of insulation makes it very easy to install. It conforms and fits nicely inside the home’s walls and as attic insulation.
  • Eco-friendly: Cellulose is made from recycled paper, which makes it highly eco-friendly.
  • Health: When properly installed, cellulose poses no health dangers to the home’s inhabitants.
Cons of cellulose insulation:
  • Pests: Cellulose is often treated using boric acid to help ward off buts and rodents, but it does not always work well, and problems of invasions are still reported.
  • Flammable: The cellulose paper is highly flammable even after being treated with chemicals to make it flame resistant.
  • Settles and Compresses After Installation: Following installation, the cellulose insulation starts to settle and compress. In some locations, it can compress up to several inches after installation, which decreases its efficiency.
  • Mold Growth: IF the insulation becomes wet, it is ineffective as insulation material and becomes dangerous because mold can quickly grow in the material. Mold and mildew rapidly grow in the paper fibers. The boric acid used to treat the cellulose becomes corrosive whenever it comes into contact with water.
  • Dust Accumulation: Cellulose is made of freshly shredded paper that can become very dusty even after installation. It is difficult to clean up and can pose a breathing hazard.

If you are trying to pick between cellulose insulation or fiberglass insulation, then you’ll want to weigh all of the pros and cons to decide which one is better for your Attic. You’ll also want to talk with a home insulation contractor to weigh their recommendations.

Conejo Valley Home Services offers complete insulation services throughout the Conejo Valley area, Los Angeles, Ventura, and Santa Barbara counties. We provide insulation services in other California locations. Contact us to learn about our free consultation.

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