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The benefits of blown-in cellulose

You don't have to demolish your walls to add insulation to your home. 

Many people have asked me about affordable techniques for adding some degree of soundproofing to existing construction. And if you live in a home or an apartment with hollow walls, you might want to blow some insulation into them.

At the very least, it will reduce the amplifying effect. That's because when you have drywall nailed on top of hollow studs, it behaves acoustically like the head of a giant drum and it echoes. And this problem plagues millions of American homes. It will not eliminate low-frequency engine noise that penetrates your building frame, such as construction equipment or large truck engines.

Here's how you can remedy this echo situation. You can add insulation without even removing the walls by getting a blower and some cellulose insulation, drilling some round holes into your existing drywall, inserting the pressure nozzle into the open space, and blowing the insulation between each stud.

Cellulose is the best loose material for blow-in insulation. 

Usually you'll find two options for blown-in insulation: fiberglass, and cellulose fiber. From my own experience, I recommend cellulose fiber and I've used it myself. It's denser, it dampens sound more effectively, it's less toxic than fiberglass, and it adds temperature insulation. Just say no to fiberglass!

In the USA, you can buy cellulose insulation (or if you insist, fiberglass) at Lowe's for less than $10 per package (covering 40 square feet each) and borrow their blower for free. (This may not be feasible for those of you in the UK who read this blog.)

This 13-minute video from Dr. Energy Saver shows you the benefits of using cellulose insulation, how it's made, and answers some of your questions about it.

This YouTube video from Bondo Built shows how you can go to a big box store, rent the blowing machine, and use plastic sheets over the openings in your walls to blow in dense cellulose. 

Remember, if you already have walls in place, you'll need a round drill to remove a small piece of drywall between each stud so the spray nozzle can access the interior of the wall. (See this video.)

When you're done, just replace the round piece of drywall, then tape and mud it, sand it, and repaint it so the wall looks like new again.


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