How Many Square Feet Are In A Roll Or Bag Of Insulation?

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The most important part of any project is preparation, and when it comes to insulating, this is especially true. When you begin this undertaking, the last thing you want is to have to head out to the department store for more materials, so how much will a roll or bag of insulation cover, anyway? We've done the research to answer this question.

A roll of insulation generally covers 40 to 75 square feet, depending on the brand. The coverage of a bag of batt insulation holds enough insulation to cover 25 to 200 square feet. 

Now that we've answered your first question, you may have others. You may still not be quite sure how to determine the amount of insulation you need for your project, or you might be wondering about rolled versus batt insulation. Keep reading to learn more.

Unrolling wool insulation in the attic, How Many Square Feet Are In A Roll Or Bag Of Insulation?

Rolled Insulation

Rolled insulation is an insulation product that comes in ready-to-be-cut rolls. Rolled insulation is already manufactured at its desired thickness and R-value.

This type of insulation is desirable because it is lightweight and easy to cut and manipulate. This means that it can be installed in tight or odd-shaped areas without trouble. It can be purchased as fiberglass, foam, or mineral wool.

A big roll of fiberglass insulation wool

What Are The Dimensions Of A Roll Of Insulation?

A roll of insulation can be found in a variety of dimensions to fit different needs and installation practices. You may also find that depending on the type of insulation desired, smaller or larger rolls will be available. For our purposes, let's take a look at some of the most common sizes for rolls of insulation.

  • For installation between 2x4 studs, you can find a roll of insulation at 15 inches wide and 32 feet long.
  • For installation between 2x6 studs, you can find a roll of insulation at 23 inches wide and 39 feet long.
  • For installation in an attic, you can find a roll of insulation at 15 inches wide and 25 feet long.

Check out this roll of insulation for 2x4 walls on Amazon.

It's important to note that the thickness of the insulation will depend upon the R-value of the insulation. The R-value is the measure of a material's thermal resistance. The higher the R-value is, the better the material's ability to prevent heat energy from passing through it.

For example, a roll of insulation with an R-value of R-19 is 6.25 inches thick, while a roll of insulation with an R-value of R-13 is 3.5 inches thick.

How Much Will A Roll Of Insulation Cover?

A typical roll of insulation will generally cover anywhere from 40 to 50 square feet. Some may desire a bulk roll for their purposes, which will cover around 75 square feet.

How Many Rolls Of Insulation Do I Need?

This will, of course, depend on the size of your project. To determine how many rolls of insulation are necessary to complete this venture, first begin by measuring the area in need of insulation. This may be a wall, a ceiling, or a floor.

Using a measuring tape, take measurements of the length and width of the area in feet. Once these measurements have been recorded, they can be multiplied. This will give you the square footage.

Now that you know your square footage, you can determine how many rolls of your chosen insulation are needed. Most products will have their coverage listed on the product itself or the product webpage.

For example, if you are insulating a wall that is 8 feet tall by 10 feet wide, you will find that the square footage of that area is 80 square feet.

If you've chosen a roll of insulation that has a coverage of 40 square feet, you will need two rolls, at the very least. However, we do strongly recommend purchasing 1-2 extra rolls to ensure that you will have enough for your project.

How Do You Install Rolled Insulation?

A small roll of fiberglass insulation

Before you install your purchased material, you will need a few other supplies. Make sure you have:

  • a box cutter,
  • measuring tape,
  • staples or wires,
  • face mask,
  • safety glasses,
  • and safety gloves.

Then it'll be time to get started. Measure your first area. If you've chosen the correct dimensions for your project, such as a product for 2x4 walls, cutting the roll to size will be simple.

Release the insulation from its roll and cut it to length. For an easy and clean cut, stabilize the insulation by leaning a knee against one side. Allow an extra 1/2-inch to your cut to ensure a tight fit.

With the moisture barrier facing outward, push the insulation piece into the crevice. Be sure that it fits correctly, sitting snugly against the studs but not being so tight that the moisture barrier protrudes out of the space.

Now you will secure the insulation using either staples or wires. Most insulation rolls come with tabs. If using staples, press these tabs either against the inner or outer sides of the studs and staple them.

If using wires, push them between the studs so that they are keeping the insulation in place. Repeat this process until the area is filled with insulation, and you'll be done!

Batt Insulation

Man holding a block of thermal insulation

The difference between batt and rolled insulation is simply that batt insulation is pre-cut. It can be purchased in a variety of sizes to fit the installer's needs.

Fiberglass, foam, and mineral wool make up the material for batt insulation. Rectangular, pressurized bags package this type of insulation. Though it is extremely easy to install for the typical project, it isn't as simple to manipulate as rolled insulation and is not so easy to cut.

How Much Will A Bag Of Insulation Cover?

The coverage of a bag of insulation will vary greatly depending on the material type and the R-value. Generally, a bag of fiberglass insulation will cover the highest amount of square footage, even up to 200 square feet. A bag of mineral wool insulation covers the least amount of square feet. This could be as low as 25 square feet.

A bag of Owens Corning R-15 mineral wool insulation only covers 29 square feet. This is while a bag of Owens Corning R-15 fiberglass insulation covers 67 square feet.

The R-value also plays a role in this determination. If you desire a higher R-value, expect the coverage of one bag to be quite limited. However, if a lower R-value, you may find that the coverage of one bag is much higher than its counterpart.

For example, a bag of Johns Manville R-38 fiberglass insulation covers 64 square feet. A bag of R-19 fiberglass insulation from the same brand covers 133 square feet.

Take a look at this R-38 batt insulation on Amazon.

How Many Bags Of Insulation Do I Need?

The process of determining how many bags of insulation are needed for your project is the same as with rolls of insulation. Begin by taking measurements of the length and width of the area that you intend to insulate. Multiply these measurements to gain the square footage.

Now that you have the square footage, compare it to the coverage of your chosen material. It's best to err on the side of caution and purchase a bit more than is technically necessary.

How Do You Install Batt Insulation?

Fiberglass insulation roll

Installing batt insulation is very similar to doing so with rolled insulation, but with this type, you should be sure that you have purchased the correct size for your project before beginning. These are manufactured for placement between studs and created in standardized dimensions.

Begin by releasing the insulation from its packaging. Make sure you have plenty of room when you do. There will be many large pieces in the small bag.

Take a piece and push it into the crevice between the two studs. Be sure that the vapor barrier faces outward toward the room. The fit should be snug, but if the batt folds or the vapor barrier protrudes out of the space, this may be an indication that you have the wrong size of batts.

After you've placed the piece, you should secure it either using staples or wires. As with the rolled insulation, you can flatten the mounting tabs on the piece against the inner or front sides of the studs and staple them there. Otherwise, you can place wires between the two studs to keep the insulation piece set up.

Repeat this process throughout the area until it is completely covered with the batt insulation. Then, the work will be finished.

In Conclusion

Unrolling wool insulation in the attic

Installing insulation correctly is so important to the comfort and economy of the home, that it can feel like a daunting task to undertake. We hope we've taken some of the pressure off by answering one of your questions about rolled and bagged insulation, specifically, how many square feet are in a package?

We've determined that a roll of insulation will cover anywhere from 40 to 75 square feet. The typical roll covers 40-50, while the bulk sizes cover up to 75. We also found that a bag of insulation can hold enough to layer 25-200 square feet, being contingent on both the type of material and the R-value.

Want to learn more about insulation? Visit these related posts:

What's The Best Insulation For Soundproofing Ceilings And Walls?

9 Types Of Thermal Insulation You Should Know

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