How to Install Fiberglass Insulation

Our expert installing fiberglass insulation at an Ontario Home

Our expert installing fiberglass insulation at an Ontario Home

Looking to get more information on how to install fiberglass insulation in Toronto Area. Check out Eco Spray Insulation expert guide to help you with that.

What is Fiberglass Insulation

Fiberglass Insulation is a material made from fine glass fibers and sand. It is also sometimes referred to as glass wool or fiberglass batts.  The thermal insulations made by fiberglass consist of intertwined and flexible glass fibers, which causes it to create millions of tiny air pockets. These air pockets are the actual insulator. Fiberglass as an insulator slows the spread of heat, cold, and sound in structures. The material does this by trapping pockets of air, keeping rooms warm in the winter and cooler in the summer.

How to install fiberglass insulation
How to Install Fiberglass Insulation 3

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Advantages and Disadvantages of Fiberglass Insulation


  • Low weight. This makes it easier to work with even in DIY projects and can shorten the time of installation on a professional install.
  • Minimal maintenance. Fiberglass is very long-lasting and requires minimal maintenance compared to other types of insulation.
  • Thermal Insulation. Without fiberglass, it would be extremely difficult to keep warm or cool. This means lower utility costs, quieter, and a more comfortable living environment.


  • Dangerous to humans. During installation, fiberglass insulation releases particulates into the air which may be inhaled by those installing or removing it. When inhaled, particles can cause coughing and other respiratory ailments.

Fiberglass for Attic Insulation

Attic insulation is a very popular home improvement project. If your attic has proper fiberglass or spray foam insulation can increase the value of your home. Also, it is capable of improving your home’s energy performance and comfort by reducing noise and keeping a standard temperature for a long period of time.

Blown-In Cellulose vs Fiberglass Insulation

Blown In Cellulose Insulation
Pros Cons
  • Cellulose insulation helps reduce the mountains of discarded paper and cardboard created by a paper-hungry society.
  • Cellulose is treated with boric acid, which increases fire resistance, resists mold and makes it unpalatable to insects.
  • Some cellulose insulations are treated with an acrylic binder which ensures it settles when installed, thus reducing the long-term decrease in R-value.
  • Cellulose is generally cheaper than fiberglass insulation (up to 25% cheaper, in some cases).
  • The R-value of cellulose (roughly R-3.2 per inch) is higher than that of standard fiberglass (R-2.2 per inch).
  • The health risks from cellulose are far fewer than those from fiberglass.
  • Installation costs for cellulose can be higher than for fiberglass.
  • Cellulose insulation creates an enormous amount of dust when it is installed, so a certified breathing mask is absolutely essential.
  • Dry-blown cellulose sags and settles, reducing its R-value over time.
  • Cellulose insulation absorbs moisture easily, which not only reduces long-term efficiency but can cause the insulation to mold and rot. Even wet-blown cellulose can suffer from these effects.
  • Both dry-and wet-blown cellulose need a vapor barrier.
Fiberglass Insulation
Pros Cons
  • Fiberglass insulation is inexpensive and effective.
  • Fiberglass does not shrink.
  • Most manufacturers supply the material in sealed batts, covered with plastic film (perforated polyethylene or polypropylene, specifically) to avoid issues with breathing the fibers.
  • The plastic covering on fiberglass batts acts as an effective vapor barrier.
  • Fiberglass insulation does not burn.
  • Some fiberglass insulation uses recycled glass, reducing its ecological footprint.
  • Fiberglass insulation is available in medium- and high-density options (roughly R-11 and R-15 for a standard 2-by-4 wall).
  • Insects do not eat fiberglass insulation (or rather, it is not nutritive to them, so they have no reason to nibble).
  • Blown fiberglass surrounds everything inside wall cavities, providing a more consistent layer of insulation.
  • Protective gear must be worn when installing fiberglass insulation: the tiny slivers will lodge in skin and are small enough to be inhaled.
  • Unless you use plastic-sealed batts, fiberglass insulation requires a vapor barrier to protect it from moisture.
  • Fiberglass blankets do not seal wall and ceiling spaces very tightly.
  • Inhaled slivers of fiberglass irritate the alveoli and can cause lung disease.
  • There is some data which suggests fiberglass in the lungs may cause cancer, by slicing DNA and causing cell mutation, in the same way as mineral wool.
  • Some fiberglass insulation still uses formaldehyde as a binder, which leaks out into the air.
  • This product may also cause cancer.
  • Fiberglass settles and sags, so its R-value decreases over time.
  • Standard fiberglass can be crammed into smaller spaces to improve its R-value, but it needs venting if this is done (to avoid moisture buildup which will destroy its efficiency).


Every time you want to purchase insulation for your home, you will notice something called R-Value. R-values show to us how well an insulation material performs creating a thermal barrier. Fiberglass and cellulose insulation have similar R-Values between 3.5 to 3.7 per inch. Fiberglass exposed in extreme cold will reduce the R-Value.

Air Leakage

It’s true that neither insulation is an air barrier. Neither cellulose (even when dense-packed) nor fiberglass meets any technical standard for an air barrier. However, cellulose will slow air flow whereas fiberglass does not. When densely packed into a wall cavity, cellulose prevents most air flow. Even loose-fill cellulose slows some air movement.

Embodied energy

Embodied energy is the sum of energy required for a project or material. Fiberglass has a much higher embodied energy than cellulose insulation. Fiberglass is glass that is melted and spun into fibers like cotton candy. There are fiberglass brands which use recycled content but more often they use new raw materials.

Most cellulose brands use a high recycled content and the production process (shredding paper and adding fire retardant borates) uses much less energy.


When comparing blown-in insulation, both fiberglass and cellulose are nearly identical in price, both costing around $0.70 to $0.80 per square foot for 6 inches of insulation. Fiberglass batts, however, are less expensive, costing on average $0.30 to $0.40 a square foot for 6 inches of insulation.

Installation costs for blown-in insulation costs around $2 a square foot, where installation costs for batts is around $1 a square foot.

So, for an average installation of a single room of 240 square feet, blown-in insulation of either fiberglass or cellulose will cost between $650 and $670, while the same space insulated using fiberglass batts will cost between $310 and $340.


While Cellulose may provide more depth and better soundproofing qualities, it may lose its R-value over the years. After installation, cellulose has been reported to pack and settle. This can cause it to form pockets in the settled areas which can transfer hot or cold air into your home. Fiberglass, on the other hand, stays in its original form and shape, which typically means it lasts longer. Fiberglass can last over 30 years and often comes with a lifetime warranty. It is also quicker to install and offers more protection against mold and mildew growth.

Environmental Concerns

Cellulose insulation is considered a greener material than fiberglass. It is made from paper that has a minimum of 85% recycled content, such as newspapers. It does not pollute the air during manufacture or use as much energy to produce as fiberglass. Fiberglass fibers may become airborne, which can be considered a pollutant. And while fiberglass uses some recycled content, it is often closer to 50%, much less than cellulose. It also takes more energy to produce.


Fiberglass, which is naturally nonflammable, is made up of sand and other natural/recycled materials, while Cellulose (made up of newspaper; magazines; and cardboard) contains artificial chemicals. This is because when cellulose is bound together to create the insulation material, the machines used are not able to filter everything correctly, leading to pieces of credit cards, plastic cups, and other wasteful products being shredded into the material. Adhesive, boric acid and stabilizer chemicals are then added to cellulose. The boric acid allows cellulose to provide protection against pests, and also makes cellulose a fire-retardant material. However, Cellulose dissipates over time and turns to dust. The chemicals in Cellulose then become airborne contaminants that enter your home’s air, specifically through light fixtures and electrical ventilation, making the air in your home hazardous to you and your family. Fiberglass, however, uses natural binders and adhesives, making it a healthier, safer, and more eco-friendly choice.

Fiberglass for Basement Insulation

The key to building better mold free basements is to understand that there is a completely different set of challenges facing walls built below grade. 

The greatest source of moisture to contend with above grade is the warm, humid air generated by cooking, washing and simply breathing. Below grade, it is that big porous sponge called concrete that is sucking up water from the wet ground.

A different problem demands a different solution – wearing a raincoat will keep you dry when standing in a cold rain, but it won’t keep you dry when jogging under a hot sun. And unfortunately for many homeowners,  the way basements were finished for the last few decades is about as logical as jogging in a raincoat. 

Above grade, walls are designed to dry to the exterior. That is impossible below grade, but for some reason, we still build as if it were. Despite the fact that interior vapour barriers in below grade wall assemblies are commonplace, frustrated building scientists insist that installing them is the worst thing you could possibly do down there.

Fiberglass for Exterior Wall Insulation

Most wall assemblies, especially those in older homes, are built with two-by-four (2×4) studs. Since modern two-by-fours are not 4 inches, the true depth of the wall cavity is 3 1/2 inches.

In most wall applications, you will use R-13 or R-15 Kraft-faced fiberglass insulation rolls for these two-by-four stud walls. While rated differently, these two types of insulation are close enough in thickness that they can both fit into modern two-by-four wall systems.

Older homes, especially those pre-dating the 1950s, may employ two-by-fours that truly are 2 inches by 4 inches. In this case, use R-13 or R-15 fiberglass insulation. There is no 4-inch thick faced fiberglass insulation in batts or rolls on the common.

Insulation for 2×6 Walls

Some newer homes may have walls built with 2×6 studs. Use R-19 or R-21 Kraft-faced fiberglass insulation for two-by-six (2×6) walls. This combination ensures that the insulation is neither too loose nor too tightly packed within the walls.

DIY Fiberglass Insulation vs a Professional Install

Before you decide on DIY insulation or hire a professional, you should make a plan determining how much insulation you need and where you need it. Because of the safety considerations even if you chose for DIY insulation, it’s best that you take professional advice. In case of little or no ventilation, possible presence of Asbestos, rotted attic rafters or wet insulation indicating leaks it’s advisable to call our professional team.


At Eco Spray Insulation, we try to understand all the needs of our customers in order to guarantee every project in the best way possible. We use only the highest quality insulation products. Using specialized equipment, the cellulose (or fiberglass) provides an effective insulation envelope, with coverage that protects all of the gaps, cracks, and crevices throughout the attic and roof cavity. Spray foam insulation is probably the best thing you could do for your home. With your help, we try to stay among the best insulation contractors in Canada.


Q: Is exposed fiberglass insulation dangerous?

A: During installation, fiberglass insulation releases particulates into the air which may be inhaled and can cause coughing and can act as lung, eye, and skin irritants.

Q: Does fiberglass stay in your lungs forever?

A: Inhaled fibers are eliminated from the body parts from coughing, the body’s defense mechanism, and through the digestive system.

Q: How long can fiberglass insulation last?

A: If fiberglass insulation is maintained properly and not damaged, it can last 80 to 100 years.

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