Attic Insulation: The Basics

This is attic insulation 101, a much-needed course to provide you the basic information about attic insulation and its types. It can be overwhelming as you read various sources, each with different opinions and ideas about how to best repair your home. There are many different types of attic insulation, ranging from cellulose insulation to rockwool insulation. There are many material types they can come in, as well. Attic insulation can be installed via spray foam insulation or insulation blowing, to name a few. Here we will discuss in a succinct, ordered manner every type of attic insulation, its benefits, and its forms. Give us a call if you ever need some further assistance. Our specialists would be happy to assist you in finding the perfect fit for your home. 


Before diving into the details of attic insulation, it is important to quickly discuss how insulation is measured. Insulation is measured by its thermal resistance capabilities. This is calculated as its r-value. The greater the R-value, the greater the insulating resistance it is capable of achieving. The r-value is created by a piece of insulation’s thickness and density. Different types of insulation have different R-values. Their prices and effectiveness, therefore, range in accordance with their r-value. Insulation is layered depending on a space’s required insulation levels. R-value requirements are based on a home’s location and the specific space. 

Insulation Materials

The most common form of heat barrier in a home is through the form of insulation. Insulation comes in many different material forms. Each material type provides specific benefits to a home and is recommended in certain instances over others. Some of the most common materials are:

  • Fiberglass insulation 
  • Rockwool insulation 
  • Cellulose insulation 

Fiberglass Insulation

Fiberglass insulation is composed mainly of, you guessed it, glass. It is mostly comprised of recycled glass that is heated to great temperatures and then spun into fiberglass. The fiberglass insulation is most often founded in the blanket form, known as “batts.” You can also purchase fiberglass insulation as loose-fill insulation. You can purchase the batts in different thicknesses, each offering a different r-value. Fiberglass insulation is the least expensive of the three material options, however, it has the lowest R-value per square inch, thus requiring more to achieve a certain thickness level. It has an R-value of 2.2 to 2.7 per inch. Fiberglass insulation is very energy efficient. It can reduce your energy bill by anywhere between 40 and 50%. It is fire retardant and noise canceling, both excellent features in a home. 

Rockwool Insulation

Rockwool insulation is another great option for your home. Also known as mineral wool, rockwool insulation is comprised of basalt rock and slag (recycled steel) that is heated to 2,900 degrees and then melted into a lava-type liquid. This liquid is then spun into fibers and then cut into the pieces of rockwool insulation. Rockwool insulation is mildew and mold resistant, as any organic matter that existed prior to its creation is eliminated. It can contain anywhere between 16 and 40% of recycled material and much like fiberglass insulation, is very soundproof. Rockwool insulation has an R-value of 3.0 to 3.3 per inch of insulation. Its greatest feature, however, is its heat retention abilities. It is fire-resistant up to 1,400 degrees. This is an excellent product for residential homes to be used between the inside and outside of the home, between bedrooms, and potentially even between floor levels. It is highly durable due to its core materials and is water resistant. 

Cellulose Insulation

The final type of insulation material available is cellulose insulation. Cellulose insulation is comprised of mainly recycled paper. It is known for its eco-friendly features, as it is made with a majority (up to 85%) of recycled materials. It is treated with non-hazardous chemicals during the treatment process to become flame, mold, and pest resistant. Cellulose insulation has a Class 1 Fire Rating, meaning that it can prevent the spread of a fire in your home and is heat resistant. Cellulose insulation has the greatest r-value with 3.5 per inch of thickness. It is one of the more expensive options due to this, however. 

Insulation Types 

Now that you know the installation materials available to you, you now have the option of choosing their type. Fiberglass, rockwool, and cellulose insulation can be manufactured into different consistencies or types, depending on your home and the needs of your space. Our specialists will be able to determine what the needs are of your home and can adjust your custom plan accordingly. Let’s discuss the attic insulation types. They are as follows: 

  • Blanket Insulation: Batt & Roll
  • Foam Board
  • Loose-Fill / Blown-in Insulation 
  • Radiant Barriers 
  • Spray Foam Insulation 

Blanket Insulation: Batt and Roll

The first type of insulation, and one of the most popular, is blanket insulation. Blanket insulation comes in the form of either batts or rolls. It is most commonly made out of fiberglass insulation. While it can also be found made out of rockwool, the majority of the time, you will purchase fiberglass batt insulation. Batts and rolls come in certain widths, able to fit between the standard spacing of walls or floor joists. R-13 and R-15 insulation come in 2x4 inch sizes and R-19 and R-21 products come in 2x6 inch sizes. Long rolls of batt insulation can be cut by hand to custom-fit your space. You can purchase batt rolls with or without facing. This facing can act almost as a vapor barrier and an added layer of insulation. 

Foam Board Insulation

Another common type of material used in attic insulation is foam board. These are panels of insulation that can be used to insulate your entire home. They are rigid and thick, thus having a greater density, allowing it to have double the insulating powers of other materials of the same thickness. They are most often used in attics that are very simply structured and easily accessible. 

Loose-Fill / Blown-In Insulation

Loose-fill or blown-in insulation is exactly as it sounds. It is simply material composed of fiberglass, cellulose, or rockwool that is blown into the attic with a vacuum. It is especially useful in spaces that are hard to reach, as these small particles are able to fill in tiny spaces and conform to any shape. The majority of blowing insulation is recycled materials. Cellulose insulation is composed of recycled paper. The majority of fiberglass insulation is composed of recycled glass. Rockwool is produced from slag, which is 75% recycled materials. Insulation blowing is conducted until a certain thickness and r-value are reached. Depending on the type of material chosen (ie. fiberglass, cellulose, or rockwool insulation), a certain height/level of loose-fill insulation will need to be blown. The R-value of loose-fill insulation does not change proportionally with thickness. Thus, there are specifically documented details of its coverage capabilities. 

The Federal Trade Commission issued an R-value regulation entitled the “Trade Regulation Rule Concerning the Labeling and Advertising of Home Insulation.” (16 CFR Part 460) Basically, this requires that insulation manufacturers and installation companies must disclose each type of insulation’s R-value and other pertinent information (ie. thickness, square footage per package). This ensures that homeowners are protected from any duplicitous schemes. 

Radiant Barriers 

Another option outside of insulation is radiant barriers. Radiant barriers, unlike standard insulation, reflect heat rather than resist heat flow. Radiant barriers are an excellent addition to attics, as they assist in reducing energy bills, especially in the hot summer. Radiant barriers are comprised of an aluminum foil-type surface, helping reflect any heat in a straight line that enters the space. When sunlight hits a roof, a significant amount of this heat travels via conduction through the roof and into the attic side of the roof. Having a radiant barrier installed in your attic will reduce the radiant heat transfer into the attic. 

We would recommend installing a radiant barrier in a home that is located in a hot climate. Radiant barriers can reduce energy costs anywhere between 5-10% in a warm climate. 

Spray Foam Insulation 

Spray foam insulation is another well-loved method of installing insulation in homes. This insulation comes in the form of a liquid. It is sprayed or blown onto the walls using a specially designed, compressed machine. Once sprayed, it begins to expand, creating a tight, immovable barrier on the walls of the space. It is an excellent method for insulating hard-to-reach cavities. 

There are two different types of spray foam insulation: closed cell and open cell. These are both commonly made from polyurethane. Closed cell spray foam is waterproof, as the cells are closed and once applied, will expand to fill the space. It has a greater R-value and is denser, causing its price to be greater, as well. Open-cell spray foam is not as dense and the cells are filled with air, giving it a more spongy texture. It is lighter and less expensive. 

Easy Breakdown

Now that we’ve discussed the material options and insulation types, here’s a quick recap of everything we’ve discussed: 

Blanket: Batt & RollsFiberglass insulation
Rockwool insulation
Plastic & natural fibers
Unfinished walls, Floors, Ceilings, Attics
Built to adhere to standard stud and joist spacing Inexpensive
Foam Board InsulationPolystyrene

Unfinished walls, Floors, Ceilings, Low-sloped roofs, AtticsHigh insulating capability
Loose-Fill / Blown-In InsulationCellulose insulation
Fiberglass insulation
Rockwool Insulation

Walls or wall cavities,
Unfinished attic floors,
Hard-to-reach spaces
Good for adding extra insulation to pre-insulated spaces Hard-to-reach spaces
Radiant BarriersFoil-faced paper, plastic film, or cardboardUnfinished walls, ceilings, attics, and floorsBuilt to adhere to standard spacing Prevent heat flow
Spray FoamPolyurethane, Cementitious, PhenolicEnclosed pre-existing wall, New wall opening, Unfinished atticSuitable for adding insulation to pre-finished areas Hard-to-reach/irregularly shaped spaces.

There are so many different types of insulation to choose from. From rockwool insulation to cellulose insulation, your home has many different materials from which to decide between. From there, you have the options to choose between insulation blowing to spray foam insulation to protect your home and maximize its efficiency. Our team of experts would love to come and provide you with a custom solution to fit the needs of your family and your home. Every home is different and each requires specialized care to ensure its longevity and productivity. Give us a call today!

Good Home Insulation

We’re committed to saving you money and safely keeping your family comfortable all seasons of the year.

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