Blown-in insulation, or loose-fill or blowing wool insulation, can be used in several different ways, 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 blown-in insulation faster, more efficiently and with better results.


How Much Blown-in Insulation Will I Need?

Like batts and rolls, blown-in insulation is also specified by R-value, but this is not the same as inches of thickness installed.  It is a caluclation of quantity of materials and rate of flowing 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 squre feet is based upon the net area of the space to be insulated.

Blown-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 blown-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.

If you decide to do it yourself, many retail outlets have blown-in products available and rental machines (sometimes rent-free if purchasing enough quantity of material).  An example of this type of coverage would be a cellulose product with an approximate cost of $11.00 a bag.  Each bag usually covers an area of not more than 40 sq. ft. at an R-value of R-26 (approximately 7-1/4").  Note:  Most often the number of bags required by a homeowner is greater due to lack of marking the attic with rulers, strings or some type of height measurement. 


Installation Tips

To start, remove any objects from the attic that might interfere with the proper application of the insulation.

Make sure that any eave or soffit vents are not blocked.

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.

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.

Load the insulation into the blowing machine hopper.  The hopper should be kept nearly full so the insulation flow is smooth and even. 

Hold the hose parallel to the floor with the insulation falling 10' to 12' away.  Begin at a far wall and work toward the center.  Always blow in the direction of the joists.  Be very careful to step only on the floor joists or you might accidentally put your foot through the finished ceiling below.

Fill three or four joist cavities by moving the hose to the right and left.  Wherever 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. 

Avoid using your hand as a baffle to direct the insulation as it comes out of the hose.  Do this only when necessary to avoid packing of the insulation.

Keep the hose close to the floor where insulation must go under obstructions such as cross bracing and wiring.  You have to blow the insulation on both sides of these.  If an obstruction has caused a low spot to occur, fill in the area.

Check the thickness of the insulation and check that you have used the correct number of  bags per 1000 sq. ft.

Cavities, drops and scuttle holes should be covered with batts.


Disclaimer:   The material on this website is to be used for informational purposes only and is not meant to substitute for any particular application due to geographic location and other unknown variances.  Links to other websites are included for the user's convenience only and do not constitute an endorsement of the material on those sites.