Does anyone have experience with cotton batt insulation? (Yes, stuff that’s made from blue denim, among other materials) A designer I’m working with wants to use it and I have a nagging voice in the back of my brain that’s repeating something about sag and other negativisms. Can any of you enlighten me on these products? Bonded Logic is at least one manufacturer.
The insulation in my attic in our new house is unusually comfortable, not scratchy - I’m thinking it is probably cotton. But it is blown, not batt. All I can say is it must be more common than I had previously thought.
I’ve got a 12x12" sample of the Bonded Logic insulation and it’s every bit as dense (if not more so) than glass fiber batt insulation.
I see two downsides to using it. One, last time I checked it’s pretty pricey. And second, well, I was about to say that you can’t use it where the code requires non-combustible materials, but I just looked their website, and the product is now Class A rated, so never mind reason #2!
We had looked at it for a project a year or so ago. We ended up specifiying it for interior partitions as acoustic batt insulation (OK in 60 minute rated walls).
However, as at that time at least it was not available with an integral vapor retarder, we did not use it for exterior wall thermal insulation.
We’ve used it once. The installation cost has proven to be considerably higher than fiberglass, in no small part because of the density - it’s heavier and considerably more difficult to handle than fiberglass. In addition, penetrations and cuts require more labor, and fitting around obstructions has proven to be difficult.
So what, in your humble opinions, is the best insulation to use if you’re resolved to be sustainable, eco-friendly, and - oh yes - going for LEED® certification?
To start, specify insulation with recycled content to qualify for MRc 4.1 & 4.2 and formaldehyde free. John Manville has such products.
Glass fiber and mineral wool (rock or slag) products meet these requirements.
Since energy consumption is such a large component of high performance buildings, my opinion is that it is more important to use more insulation of whatever type you select.
Cotton also holds more moisture than fiberglass insulation, which can be a problem in some installations. If you’re concerned about LEED, you can get all the material credits you need without worrying about the insulation as long as its not toxic. I had owners who were concerned about the worker comfort – but if the installation is done properly and the walls sealed up, there should be no fibers floating around anyway. use more insulation and don’t worry about cotton unless you’re in a very benign, very dry climate.