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How to Install Blown-in Insulation

Insulation Tips for Blown-in Insulation

Blow-in insulation (also called loose fill or blowing wool insulation) can be used in several different applications, but it is especially useful in unfinished attics or attics with hard-to-reach areas.

You can rent an insulation blowing machine at many home improvement and equipment rental centers. However, depending on your budget and the size of the area you are insulating, you may want to hire a contractor. A trained professional may be able to install your blow-in insulation faster, more efficiently and with better results. For tips on when and how to hire a contractor, click here.

How Much Blown-in Insulation Do You Need?

Like batts and rolls, blow-in insulation is also specified by R-value, but this is not the same as inches of thickness installed. It is a calculation of quantity of materials and rate of blowing needed to reach a desired density and height of material and cover the entire space. To achieve the desired R-value, it will be important to follow package labeling. The minimum number of bags per 1,000 square feet is based upon the net area of the space to be insulated.

Blow-in insulation is highly compressed in the bag. The blowing machine is designed to open up the insulation material, fluff it, and then blow it out through the hose at the rate you set to achieve the specified coverage and R-value.

A useful guide for installing the proper amount of blow-in insulation is to mentally divide the space into four equal parts. Then you can figure how many bags should go into each quarter of the space. For example, if you have 24 bags of insulation, you would blow six bags into each of the quadrants.

How to Install Blown-in Insulation

Machine Instructions

Click here to download the machine instructions

Installation Tips

  1. Remove any objects from the attic that might interfere with the proper application of the insulation.
  2. Make sure that any eave or soffit vents are not blocked.
  3. Place one or more attic rulers in each quadrant of the attic space. This will help you know when you have achieved the correct depth of insulation.
  4. Load the blowing machine hopper with insulation. The hopper should be kept nearly full so the insulation flow is smooth and even.
  5. Hold the hose parallel to the floor with the insulation falling 10' - 12' away. Begin at the far wall and work toward the center. Always blow in the direction of the joists. Be careful to step only on floor joists, or else you might accidentally put your foot through the finished ceiling below.
  6. Fill three or four joist cavities by moving the hose to the right and left. Where possible back away from the work to avoid packing the insulation. Be sure to get insulation to the top of the walls and low places. Don't cover eave vents.
  7. Avoid using your hand as a baffle to direct the insulation as it exits the hose. Do this only when necessary to avoid packing.
  8. Keep the hose close to the floor where insulation must go under obstructions like cross bracing and wiring. Insulation must be blown on both sides of these kinds of obstructions. If an obstruction has caused a low spot to occur, fill in the area.
  9. Check the thickness of the insulation, and check that you have used the correct number of bags per 1,000 sq. ft.
  10. Cavities, drops and scuttles should be covered with batts.

When and How to Hire a Contractor

Insulation contractors are trained in the installation of many different types of insulation. Plus, many offer additional installation services, such as fireplaces, doors and windows, and closets. Insulation contractors may work directly with your builder or can be hired directly by homeowners for new construction jobs or retrofit. It is always good to meet with and receive bids from a few contractors, making sure to thoroughly explain your needs. Most contractors will offer upgrade packages and can often explain the energy savings benefits of such upgrades.

To find a contractor in your area, use our Contractor Locator.

Related Products

Attic Protector® Loose-Fill Fiber Glass Insulation


Johns Manville's Attic Protector® loose-fill fiber glass insulation is made for open attics to fill nonconforming spaces and hard-to-reach areas like corners, edges and around framing.

Climate Pro® Loose-Fill Fiber Glass Insulation


Johns Manville Climate Pro® loose-fill fiber glass insulation is made for installation in open attics to fill hard-to-reach areas like corners, edges and around framing.


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