I recently wrote an article comparing fiberglass insulation to stone wool. It seemed like a fair comparison because they are both mineral wools that are typically installed in cavities as batts. Today, I thought it would be fun to do a similar comparison of cellulose and denim because they are both eco friendly insulations made from recycled, plant-based materials.
What Is Cellulose Insulation?
Cellulose is just a fancy word for wood fibers. When it comes to cellulose insulation specifically, it is a batt or loose-fill insulation made from recycled paper and cardboard – predominately old newspapers. Once the paper has been broken down and all the unwanted debris has been separated, it is treated with borate – boric acid – to prevent decay, fungus, and to make it fire resistant.
What Is Denim Insulation?
Denim insulation is made from recycled cotton – predominantly donated blue jeans, though it may also contain strands of yarn and other fibers. Just like cellulose, it is treated with borate for the same reasons.
Comparison of Cellulose to Denim
Even though these materials are highly comparable, there are some subtle differences you may want to take into consideration.
The cost of these materials is fairly comparable, with denim usually being a little bit cheaper. However, loose-fill cellulose should be installed professionally, which I’ll get into a bit more, and that could significantly increase the cost per square foot. It’s also worth noting that neither of these materials are cheap. At the time of writing this, they both cost about twice as much as fiberglass.
Both insulators have the exact same R-value per inch: 3.5. Interestingly, this is a slightly higher value than batt glass wool and stone wool.
Neither cellulose nor denim are very water resistant, but denim is far worse in this area. Denim soaks up bulk water like a sponge, and it makes sense… If you’ve ever been caught in a rainstorm with a pair of jeans or a denim jacket on, you know what I’m talking about. Surprisingly, cellulose is more water resistant but still soaks up moisture.
In either case, both materials are hydroscopic. That means they absorb moisture. For that reason, I don’t think either would be the best choice in a climate that gets excessive rainfalls or is prone to flooding.
Cellulose and denim are equally fire resistant. They are both treated with the same fire retardant chemical, so it makes sense that they would be identical in this case. Both materials will singe but won’t ignite.
Neither type of insulation could be used to completely soundproof a space, but they both have fairly high STC – sound transmission class – and NRC – noise reduction class – ratings, with denim coming out slightly higher. If your goal is to dampen sounds between rooms, denim might be a good choice for your project.
Ease of Use
Denim is installed as batts, exactly the same as fiberglass or stone wool batts. It can be easily cut with scissors, though many consumers have complained about difficulties cutting it – I assume they perhaps were trying to cut it with a knife or razor, which is much more challenging.
Cellulose can also be installed as a batt, but is more commonly blown in. If blown in, it should be done by a professional.
Each of these insulators have similar flaws. Denim will rather quickly sag and compress under its own weight. It’s just not very rigid. For this reason, you are probably better off over filling the cavity a little bit. Cellulose has the same problem, though I think it doesn’t happen quite as quickly.
In batt form, they also share a similar flaw: If you try to fluff them up, stretch them, or manipulate them in any other way, they’ll likely tear/fall apart.
Both insulators are made entirely out of recycled materials; both types can be recycled again; and both can biodegrade, though it would likely take much, much longer than usual due to the borate. It’s difficult to declare a clear victor in this category.
There are no known health risks associated with cellulose or denim. You do not have to wear gloves or a respirator while handling them, though I would still wear a dust mask.
Even though these materials are marketed as green solutions to other types of insulation, and it’s hard to argue with the fact that they are recycled, recyclable, and biodegradable; there is one criticism: Both cellulose and denim are byproducts of a culture and economy that wastes a huge amount of cotton and paper.
In particular, the use of denim in fast fashion is problematic. There is a pretty big eco cost to making just one pair of jeans. However, I’m not a fan of this criticism. Again, these products are byproducts. They are not driving the waste produced by these industries. Instead, they are making use of waste that would otherwise end up in a landfill.
It’s difficult to give a hard edge to either insulator. For the DIY-er, I think denim is the better choice for wall and ceiling cavities. On the other hand, I think blown-in cellulose is better for attic roofs and attic floors.