What is Insulation?

Most homes are constructed with a material called insulation. This material is called insulation, and it’s placed between the exterior – and sometimes interior – walls before drywall is installed. 

Insulation is used to stop the passage of electricity, heat, or sound from one conductor to another. A conductor can be the sides of walls, ceilings, or doors, and nearly 40 percent of the conditioned air in a home will be lost without proper insulation.

What is insulation made of?

There are many different types of insulation, but the most common are cellulose, fiberglass, polyester, and mineral wool. These are produced using recycled waste materials, such as recycled paper products, glass, and plastic. Spray foam insulation has proven to be the most effective material, though typically the most expensive.

A stack of batt insulation with gloves, safety glasses, and a mask.

What is the R-Value in insulation?

R-Value is a formula that divides the temperature difference between a barrier’s warmer and colder surface by the heat fluctuation through the barrier. In simpler terms, it measures the insulation’s resistance to heat flow.

Different types of insulation have varied effectiveness per inch of material, and every type has a specific R-Value. All walls, attics, floors, and crawl spaces have an R-Value range determined by geographical and environmental factors.

What are the different types of insulation?

Insulation comes in many forms, each with its own benefits and disadvantages. Recycled materials have been used for decades, offering lower prices and sufficient reduction in heat transfer. A few recycled materials that are commonly used for insulation:

  • Cellulose (recycled paper products)
  • Fiberglass (recycled glass, produced as batts or blown-in)
  • Rockwool (mineral-based, typically made of steel byproducts)

 Although they have many benefits, they do not perform as well as other insulation materials. Spray foam insulation is the most highly recommended for its ability to resist airflow in crevices and corners completely. A few spray foam options include:

  • Open cell spray foam (allows some airflow)
  • Closed cell spray foam (allows no airflow)

 Regardless of the type of insulation used, all can have additional insulation installed overtop of existing material to meet R-Value standards. Though, spray foam typically does not need to be replaced or updated.

What is cellulose insulation?

Cellulose insulation is a fiber that is generally 82 to 85 percent recycled material. The material is recycled paper products, but primarily newsprint, and is heavily treated with fire-retardant chemicals.

It has a high R-Value, is generally cheaper than other options, and is mold and insect repellant, though it is prone to sagging and settling and becomes ineffective over time.

A chart explaining cellulose insulation.
A chart explaining fiberglass insulation.

What is fiberglass insulation?

Fiberglass insulation is extremely fine glass fibers typically made of 30 percent recycled materials. It is a natural fire retardant with noise-canceling properties. The R-Value for fiberglass is limited, ranging from R-11 to R-19 for walls and reaching R-30 for ceilings and attics. 

Before choosing fiberglass to insulate your home or building, consider the following:

  • It is not efficient at repelling moisture (therefore not ideal for regions with high humidity)
  • It is a thriving environment for mold spores to settle
  • Not effective against air leaks

What is Rockwool insulation?

Rockwool (a brand-specific type of mineral wool insulation) is a recycled stone-based mineral fiber insulation. It is composed of basalt rock and slag, a recycled steel-making byproduct. The materials are heated to over 2,900 degrees Fahrenheit to liquefy and mix them together. The mixture is then stretched into fibers, compressed, and cut into slabs. 

Mineral wool insulation contains about 75 percent recycled materials, while the brand-specific Rockwood contains between 16 to 40 percent.


Mineral wool can remain stable for as long as the building stands due to the materials and construction method. This factor ensures positive thermal performance for possibly a lifetime.

A chart explaining rockwool insulation.

What is batt insulation?

Batt insulation, also known as blanket insulation, is made of either fiberglass or Rockwool and is manufactured in pre-cut, industry-standard-sized sheets.

A chart explaining batt insulation.
A chart explaining blown-in insulation.

What is blown-in insulation?

Blown-in insulation (or loose-fill insulation) is the process of blowing loose insulation into cavities or attic floors. Stud or joist cavities tend to be at an awkward angle, requiring a loose material to fill the spaces. Cellulose insulation is a common type to be blown in, though fiberglass is also used. 

Fiberglass is not recommended for blown-in installations due to the adverse health effects of loose glass fibers in the air. It can penetrate the skin and irritate eyeballs, among other things.

What is the difference between loose-fill and batt insulation?

Loose-fill insulation, also considered blown-in insulation, consists of recycled materials of your choice, while batt insulation is large rolls or blankets of similar materials. Fiberglass, cellulose, or stone wool is typically used in these options. 

What is spray foam insulation?

Spray foam insulation is comprised of two chemicals, isocyanate and polyol resin. These chemicals react with each other and expand over 60 times their liquid volume once sprayed. Although spray foam is the most expensive insulation material, its benefits outweigh the cost:

  • It squeezes into cracks and crevices
  • Won’t get caught on wiring or pipes
  • Won’t settle over time 
  • Resists mold and bacteria
  • Allows virtually no air infiltration
  • Is smoke and fire retardant
  • A highly effective sound barrier
A chart explaining spray foam insulation.
A chart explaining injection foam insulation.

What is injection foam insulation?

Injection foam is used to seal enclosed cavities in existing builds to improve insulation and resist air movement. It can be injected without removing the original fiberglass insulation, though loose cellulose tends to require removal. 

This foam is composed of the same materials as spray foam but is installed differently. It is exceptionally convenient for homeowners looking to increase their insulation R-Value.

What is the difference between open and closed-cell spray foam?

Open and closed-cell spray foam use the same materials, though they have different consistencies.

Open-cell spray foam is what it sounds like. The cells of the foam are small bubbles that aren’t encapsulated, meaning they are deliberately left open. The flexibility of the open cell foam allows water to move through it, which assists in identifying leaks sooner for repair.


Closed cell spray foam is more rigid and inflexible since the cells are closed. It was designed to reject bulk water in flooding situations.