Myths & Misconceptions
- Cellulose settles in your walls
Dense-packed cellulose doesn't settle, because it can't. It's installed at twice its settled density, which means that it's under slight pressure in the wall or ceiling cavity. Those home show displays that show cellulose settling, or worse, blowing around in a box? They're tricks. They're purposely under-filled to promote the myth that cellulose settles and help them sell you some other product. Don't be fooled.
Cellulose insulation is made from newspapers, so it will burn
Cel-Pak and Nu-Wool have an 83% recycled content, primarily over-issue newsprint and other ground wood paper sources. The paper is fully fiberized (reduced to cellulose fiber) and infused with borate, a naturally occurring mineral. Borate gives cellulose a Class A fire rating. In fact, a cellulose insulated structure is arguably safer than one insulated with another insulation, because borate treated cellulose helps limit the spread of a fire and produces no smoke.
Cellulose is expensive
As a rule, cellulose insulation costs more to install than glass fiber and less to install than sprayed foams. Cellulose offers performance advantages that go beyond R-Value, so the extra expense is quickly recovered, and the savings just go on and on. Because cellulose offers comparable savings to typical sprayed foam installations, you save money at installation, and the savings just continue. So we believe the right answer is that cellulose represents the best total value, dollar for dollar, among common competing insulations.
Cellulose produces funny smells
National Fiber's Cel-Pak and Nu-Wool cellulose insulations are all borate formulations (for fire, pest and mold resistance). Borate is on odorless mineral that doesn't outgas, which is a fancy way to say National Fiber's cellulose products don't produce funny smells. Some cellulose manufacturers use an ammonium sulfate/borate mix. That can produce objectionable odors, under the right conditions. If you insist on our all borate formulations, you'll never have this problem.
Houses need vapor barriers
Cellulose insulation requires no vapor barrier in the overwhelming majority of installations. It does an excellent job of limiting air movement, and because it is hygroscopic, it manages moisture as well. Some insulations require vapor barriers because they do such a poor job of preventing air movement, air that can carry moisture with it. The problem is that, where we live, moisture and air don't always move in the same direction through a building, depending on the time of year. So what about those products that need a vapor barrier? Effectively, half the year it's on the wrong side of the wall! Cellulose doesn't have that problem.
Sprayed foam insulations can be green, too.
Sorry, no way. The only thing green about sprayed foams is the money you pay for them. Sprayed foam insulations are made with petroleum and petroleum byproducts, and that just isn't green.
What about soy based foams?
Sorry, we don't think they're green. First, they're not soy 'based' - they contain a small amount of soy additive. While soy added to foam does save a little bit of oil or chemicals, the soy had to be grown, watered, fertilized, harvested, trucked, processed - well, you get the idea. Foams with soy additive are heavily marketed for their soy content, which is something called 'greenwashing'.
For more of our thoughts on what makes an insulation green, see our What's Green? page.
Unlike cellulose, foam insulations air seal and insulate at the same time
They can, certainly - but only where they're actually sprayed. There are areas that aren't routinely foamed, like the junction of a wall's bottom plate with the floor, or the top plate with upper story framing and flooring, etc. The bottom line is that proper installation of any insulation should include comprehensive air sealing. If a foam installer tells you that by simply spraying the cavities (stud and rafter bays) the building has been air sealed, well...
We also have a lot of experience inspecting structures in the field that says that foams, especially the more rigid foams, don't have the flexibility to move as the structure does. That means there can be cracking, and separations between the foam and the framing members, as the lumber dries, shrinks and moves, which can allow air infiltration.
R-Value is R-Value, so if the numbers are the same, the products perform the same
R-Values are determined in labs, and they only measure one of the four ways that heat moves through a wall. For instance, there's no wind in a lab. So if we compare an R-19 glass fiber insulated wall to an R-20 cellulose wall on a 20-degree day in February, with a 20-mile an hour wind, that glass fiber wall may be delivering real-world performance well below R-19. (The R-Value of the glass fiber hasn’t changed, but R-Value doesn’t measure heat energy transfer due to the movement of air through the insulation.) The cellulose wall? Still performing at R-20.
I just want my insulation to do a good job insulating
Of course, you want your insulation choice to do a good job insulating. But to do that, it has to do a lot of things - effectively prevent air infiltration, manage moisture, etc. And you don't want it to create problems - make a good home for pests, outgas, etc. And then there are things you want it to do that you might not associate with an insulation product, like make your home safer in the event of a fire, do the best job of reducing noise, and have the least impact possible on the environment.
National Fiber's Cel-Pak and Nu-Wool insulations do a great job at all the things a great insulation should do, with none of the potential downsides.
Cellulose is made from paper, so if it gets wet, that's a problem
First, no insulation will handle a failed structure or assembly that is allowing liquid water to enter in any meaningful quantity. None.
With that out of the way, the other moisture that you find in walls is airborne humidity. Among commonly used insulations, cellulose is the only one that can manage this moisture by dispersing it and transporting it through the cavity. In other words, cellulose manages the natural moisture drives that occur in every structure. No other commonly used insulation product can make that claim.
Sprayed cellulose is applied wet - and that's a problem
Nope. Spray applied cellulose, which is most often used in new construction, is damp-sprayed, not wet - an important distinction. In the old days, it was a wet applied product, and you could squeeze liquid moisture out of it. For quite some time now, only a very small amount of moisture is added to damp-sprayed cellulose, definitely not enough to be able to squeeze water out of it. Under normal conditions, the cellulose is ready to be covered by drywall in 24 hours, far less time than is routinely scheduled between the insulation and the drywall jobs. In addition, cellulose manages moisture. (see 'Houses need vapor barriers', above)
I just need to insulate my attic, so can I do it myself?
Well, you could - but that doesn't mean you should. There is a proper way to install cellulose, and lots of ways that aren't. A proper loose-blown attic job will be inspected for problems, may have old insulation removed, have the soffits blocked off, have air-sealing done - you get the picture. There's more to it than just renting the machine and blowing the cellulose. (And lots of those big box cellulose products aren't as clean as National Fiber's, and many have ammonium sulfate in them - see 'Cellulose produces funny smells', above) Besides, don't you have better things to do with your weekend?
Do yourself a favor - locate a qualified installer and have the job done right.