Blown-in attic insulation: how to install it



My home’s expansion is now complete. A friend told me that blown-in insulation is superior to batts since it seals the joists. Do you have any DIY recommendations?


You are right, of course. When correctly placed, blown-in insulation provides a superior attic seal to batts.

Before you begin insulating, you must determine the size of your attic space. Depending on the weather in your area, you’ll want to aim for an R-value of R-30, R-38, or R-49 in your attic insulation. If you have an idea of the size of your attic, you can use the chart on the insulation’s packaging to figure out how much you’ll need.

It’s essential to take stock of your materials before you begin. The following items are required if your property already has recessed lighting, ceiling fans, and eave vents:

Insulation with Loose Fill

Boxes of Cardboard


Tissue Tape

Staples, or the Staple Hammer,

Blade, Utility


A blower machine for insulation is something you may rent from a home improvement store.

Before you can blow insulation into the attic, you’ll need to prepare it. Put on a long-sleeved shirt, safety goggles, and a dust mask. There must be at least four inches of clearance between the flashing and the recessed lighting for proper installation. Make a cylinder out of flashing by cutting it to size using a utility knife and taping its ends together. Install over can light with a four-inch gap. This makes it possible for hot air to escape. Kitchen and bathroom exhaust fans installed in the attic should undergo the same procedure.

Baffles are the next component. No one likes having to do this. Install the baffles using a staple hammer at the junctions of ceiling joists and roof rafters. Ensure the baffles are installed only over the vents and are high enough to prevent the ducts from being blocked by insulation. You may want to come down from the attic after installation to rest.

The next stage in getting ready is to construct a dam over the opening to the attic. The most straightforward approach is to add a few cardboard baffles to the lengths you’ll need for insulation, plus an additional four inches. You can quickly secure them by simply stapling them around the opening. This will ensure the insulation you are blowing in has the same depth.

Have a helper wait outside while you load the insulation-blowing machine, and you won’t have to make as many trips into the attic. Advice: once the fiberglass insulation has been poured into the machine, have your helper add about a cup of water per bag and spread it over the top. The insulation will lay more uniformly and generate less static if you do this before blowing it into place. It will be many minutes before another bag of insulation is required, so be patient after loading the first one into the hopper. Maintain discipline over your assistant. So that you don’t get caught up in the hose, have him climb the ladder and remove it from the attic.

In my experience, installing insulation by blowing it into the attic is straightforward. The attic’s beginning and its extremes. Check for smoothness and evenness as you travel back and forth. Don’t forget the rafters, and don’t forget the vents and open light spaces in the attic! Check the levels sometimes using a tape measure that you should bring along. For instance, if you’re putting in fiberglass insulation with an R-value of 38, you’ll want to ensure it’s at least 16 inches deep. Ensure your assistant clears the way for you as you approach the attic hatch. When you are within six feet of the hole, stopping the machine and climbing down the ladder is safe. Finish the installation once you’ve climbed the ladder, ensuring the water level is even with the dam you constructed.

The last step is to carefully replace the attic hole lid after inserting a batt of insulation into the access hole. You may now leave. Once the R-value of loose-fill insulation is reduced by being trodden on or crushed, it is best to avoid the attic as much as possible going forward.

DIY Today employs Jerry Holt as a contributor, but he also works as a freelance writer.

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