Skip to main content

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 this problem plagues millions of American homes.

You can remedy this 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.

The video below, from Advanced Home Energy shows cellulose getting blown into studs with no drywall in place yet. 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.


Popular posts from this blog

Blow-in cellulose and your hollow walls

It's not too late to insulate.  A few years ago, most American homes had no insulation in them. When a homeowner did insulate, it was usually with fiberglass batts. Then along came some better products. One of them is blow-in cellulose insulation. Does it work? I can attest to this: YES. I've used it in walls and ceilings, and it works quite well for airborne noise. If you live in an uninsulated home and you hear your neighbors voices coming through your walls or ceilings, cellulose will dampen that noise or mute it entirely. It doesn't work for all types of noise. But it doesn't eradicate impact noise. You might still hear the sounds of someone walking across a bare hardwood floor with their shoes on, for example, or hear wall-mounted cabinets opening and closing. There are other solutions for that, and by combining different solutions you can control most structural noise and create more privacy. Low cost Blow-in insulation is inexpensive. You can hire a

Combining QuietRock and Green Glue together

Two great products work great together. As I've mentioned before, I'm experimenting around with ways to reduce some of the noise problems in my apartment on a tight budget. I think I've found the best combination to date: adding a layer of QuietRock 510 over an existing layer of gypsum drywall with a layer of Green Glue inbetween. This was sort of the best of both worlds: taking a pre-made, sound-dampened drywall and then adding it over a powerful, viscous layer of glue....onto drywall that was already on the wall studs. No demo needed. In this project, I basically added two sound-dampening layers to the original 1950s drywall (one layer in the QuietRock and the other layer created by the Green Glue) to address " flanking noise ": feet, furniture, and shoes pounding on the bare floor of my downstairs neighbors' apartment. The amount of banging, bashing, and foot-stomping sounds coming from their very "wooden" apartment has been severe, and I&

Example from Roxul: insulating a home theatre room

I liked this video from Roxul because the presenter clearly explains the difference between the two types of noise: airborne and low-frequency noise, which I will add to here. The lower frequencies travel through the wood studs. A low frequency travels from your wall surfaces, floors, and ceilings if they sit directly on those studs. Lower frequencies include bass from your stereo, impact sounds from walking or pounding, trucks driving outside, and maybe the spin cycle on a washer. Roxul  insulation mitigates the other kind of noise -- airborne noise -- which can include talking and TV (without bass). This insulation product is dense and does a really great job of blocking airborne noise. However, used alone, it doesn't stop low-frequency noise. The presenter shows how to insert Roxul batts between the studs, which you've seen before. Then he installs a resilient channel to keep the drywall from touching the wood studs. The resilient channel's job is to reduce the lo