How to Blow Insulation into Existing Walls

Blown-in insulation is a quick way to add insulation to your home. You can put it in your walls, attic, crawl space, and even under the floors. It is a very versatile as far as its ease of installation is concerned, but the one problem a homeowner can face is installing blown-in insulation inside existing walls.

This is especially a concern with older homes where insulation was more of a luxury than a necessity. The following article will show you how to install this type of insulation into existing walls without removing drywall, blowing cellulose fibers between the studs.

Step 1 - Create Access

Staring down a sealed wall and needing to add blown-in insulation to it can seem like an impossible task, and even more impossible because of the mess you could make doing this yourself. Rest assured that it is actually not that hard to do and there does not have to be too much mess involved.

Place your drop cloth tight against the wall where you will be working. This will catch excess insulation and dust from the drywall. Then, use a stud finder and make a mark at each stud. Cut a two-inch diameter hole in the drywall with the hole saw and carefully remove it. Don't lose this piece as you will use it again later. Try to place the holes close to the top of the wall. This allows the cellulose to fall naturally, settle, and pile.

Step 2 - Install Blown-in Insulation

You will need a friend to help with this part of the project. Place the head of the blown-in insulation hose into the hole and continue to let it drop towards the bottom. Wrap and hold a rag around the hose where it touches the wall, and have your friend turn the blower on. As the cavity fills, pull the hose out of the hole.

Go slow to ensure the cavity gets packed tight. As soon as you feel resistance near the top of the cavity have your friend turn the insulation blower off. Carefully remove the hose and repeat with every hole you made. It is very important to work methodically and carefully.

WARNING: Always use protective glasses, gloves, and a protective mask while blowing in insulation.

Step 3 - Seal the Holes

You have just filled your walls, but now you have a bunch of holes in the drywall. You cannot leave it like this, so it has to be patched up. Saving the drywall discs you cut in step one is what allows you to make this an easier job than it seems. Try to keep the discs in order of cutting because if you made a slip of any kind the piece may not fit in other portions of the wall. Carefully slide a disc into the hole you cut. Have your friend hold the disc in place as the blow insulation may push against it. Apply drywall tape to secure it and then finish the job with spackle. Afterward, you will obviously need to repaint the wall for a uniform look.

With that, your walls are now insulated and patched. Now you can sit back and watch how much you save on your energy bills each month.

Blow Insulation into Existing Walls FAQ

How do you add insulation to walls without removing drywall?

It is possible to add insulation through a hole that is one to two inches wide. Both spray foam and cellulose can be blown into the spaces between walls using a small hole and a hose.

Once the insulation is blown inside, the little holes can be filled with wood filler, smoothed over, and covered with paint.

What is the best insulation to blow in existing walls?

Both foam and cellulose insulation can be blown into walls that are already finished. Each material has its own strengths and weaknesses.

Spray foam can be almost too airtight, limiting ventilation. However, cellulose can break down and shrink over time as it settles, lessening its insulating abilities.

Can I blow insulation myself?

It helps if you have someone to work with you when you're blowing insulation into existing walls, but adding insulation this way can be done alone and it can be done as a DIY project.

Can you have too much blow in insulation?

It is actually possible to put too much insulation into your home. Too much insulation restricts airflow and prevents ventilation, which isn't good for the house.

When a house has no ventilation at all, moisture gets trapped with nowhere to go and no way to dry. This can lead to mold.

Can you put insulation over old insulation?

Most of the time, you can add new insulation on top of existing insulation. As long as the existing insulation is not wet or moldy, there's no reason new insulation cannot be added.