How Far You Can Blow Insulation: Cellulose & Fiberglass

Maintaining the optimal ambient temperature in your home can be quite expensive especially if you live in an area with extreme weather conditions. But what if you could cut the cost by a huge 20%? Fortunately, that is what home insulation does!

Batt and roll, blown-in(loose-fill), and rigid boards are some of the insulation mechanisms you can employ to regulate your in-house temperature. All these have different costs, merits, drawbacks, and even application procedures. Loose-fill can either be installed using a machine called a blower or by hand.

If you are installing blown-in insulation using a blower, you may be asking yourself how far can the insulation be blown? And to answer your question, we discuss:

  1. The types of blown-in insulation 
  1. How the blower works 
  1. How to properly install the insulation 

Types of Blown-in Insulation


Primarily, cellulose insulation material consists of recycled newsprint paper products.  The paper is usually cut into smaller pieces that are then fiberized.

Most companies add boric acid mixed with ammonium sulfate to impart insect and fire resistance.

Generally, cellulose packs well into spaces to inhibit air flow and insulate without the need for a moisture barrier.

Whether a new or old home, cellulose can be used as loose-fill in attics and also packed in wall cavities. The depth you pack depends on the desired R-value. For every inch of cellulose insulation, the value is between 3.2-3.8.

The procedure for installing cellulose insulation in existing structures is quite different from new home insulation installation. For new construction, you can either damp spray or install it dry behind netting. You can choose to do it yourself or hire a professional depending on your needs.

Fiberglass blown-in

Made from recycled glass, fiberglass is the most common insulation installed in homes today. The glass is first melted then spun into superfine fibers.

With an R-value of 2.2-2.7 per inch, it is the lightest of loose-fill materials. Consequently, it settles more and you will need to pack a thicker layer to achieve the appropriate R-value in comparison to other insulations.

Fiberglass is moisture and fire resistant but can cause skin irritation or respiratory reactions therefore you must put on protective gear when handling it.

It can only be applied using a blower.

How Insulation Blowers Work 

 The blown-in insulation machine consists of the hopper, blower/compressor, and hose. The insulation is fed into the hopper, which looks like a metallic bin, where the bundled material is broken down into smaller pieces by rotating rods. Air pressure created by the compressor blows out the insulation from the hopper into the hose which is directed at the area to be filled.

On the blower, there are controls for adjusting the insulation flow rate and air pressure. Classically, you start with medium-high pressure and low flow rate to prevent hose clogging that occurs with a high initial insulation flow rate. 

Noteworthy, if you set a very slow delivery rate, the cavity filling time is prolonged and the insulation gets too compacted. This will cause bulging of the cavity panelling. Precise control is, therefore, necessary to ensure the cavity fills seamlessly without clogging the hose.

Typically, insulation blowers are either electric or gasoline-powered. But the latter is more effective making them the preference of many insulation companies. Their superior performance, however, comes with a much higher cost compared to the electric powered machines.

With smaller electric machines, blowing fiberglass can be quite an uphill task, and the results averagely satisfactory. Some electric blowers have been fitted with rotating metals; a modification that greatly improves their efficiency even when installing fiberglass insulation.

For enhanced performance, you require graphite powder for your blower hose. You mix one cup of graphite powder with a half-full standard hopper of insulation. (Adjust the measurements depending on the hopper size.) You then blow the mixture through the hoses severally and direct it back to the hopper where you can collect it for reuse later on. This is the most effective way of preventing blower hose clogging.

How To Properly Install Insulation Using a Blower

Installing loose-fill insulation using a machine requires two individuals. One person operates the blower unit from the utility room; controlling air pressure and feeding insulation into the machine while the other directs the hose and blows the insulation into the attic.

Before you begin, ensure the attic is air-sealed for optimal performance. Check for gaps around the attic windows, pipes, chimneys, exhaust fans, ducts, wires, and flues. Depending on their sizes and location, you can seal them using spray foam, caulk, furnace cement, or caulked metal flashing. Otherwise, the gaps will let the heated or cooled attic air escape to the outside making insulation less effective.

Other preparations you should make include fixing any roof leaks and wearing protective gear for your safety.

Installation begins with connecting the hose to the blower and feeding the loose-fill material into the machine. Switch on the hose and blow the insulation.

Start by filling the farthest point from the hatch door so that you don’t trample on the insulation you have blown. The depth of filling depends on your desired R-value that is largely determined by the area’s climatic condition. For cold places, R-49 is the estimated suitable value while it is 30 in warm regions.

Calculate the amount of insulation you need by measuring the attic length and width to get the square footage. Use the table on the back of the insulation package for reference and determine the filling depth that will give the right R-value. Online R-Value Insulation Calculators can also help you with the math.

You can also use the online calculators to determine the appropriate filling depth for your attic based on the material used and the intended R-value.

The insulation must be spread uniformly without blocking the rafter vents for better results. And when dealing with fiberglass loose-fill material, exercise caution to avoid blowing out the already filled areas because it is quite lightweight.

In case the insulation must go below obstructions like wiring, keep the hose close to the attic floor and blow uniformly on both sides of the object.

For those intending to use the attic for storage, raising the floor before adding a second insulation layer is necessary. This you can do by building a board framework over the joists, then insulating the frame too.

Hatch is the last part of the attic to be handled during the blown-in attic insulation application. You attach weatherstripping to the frame followed by fixing a piece of rigid foam on the hatch door with glue or cap nails.

Did you know that most insulation is made fluffy to trap air? So don’t pack your insulation too tightly that air, which is a good insulator, escapes leading to a poorer outcome.