One of the toughest decisions in green building is the choice of insulation. Each type has its own set of virtues and problems. Last summer I wrote an article to try and address this confusion. I didn’t even mention rock wool, and have pretty much always sort of lumped it together with fiberglass.
Not so; architect Greg Lavardera claims that it is very different, and if " you think that Mineral Wool batts are similar enough to Fiberglass batts that you already know what you need to know about it, then you are a fool." So, fool that I am, I continued reading.
Batt Insulation
Greg first makes the case that batt insulation has merits that we overlook.
Mineral Wool Insulation
Greg concludes:
Then Greg shows an installation in a factory, with walls laid on their sides, with a big mitre box cutter to make the cutting of batts perfectly square. Except in the real world that isn’t the case; there are wires, there are studs that are not perfectly square, they are using a knife instead of a mitre saw, and they are getting paid by the square foot like every other batt installer. Then all the virtues of the insulation disappear and it becomes as leaky and awful as fiberglass. Call me a fool, but I do not see how the stuff is intrinsically going to result in a better installation. In BuildingGreen’s Guide to Insulation Products and Practices, he writes about mineral wool:
Cellulose Insulation
Greg then turns the rant away from support of mineral wool to an attack on cellulose, the darling of the green building industry. I have never been comfortable with the stuff, and neither is Greg.
I am not certain that this is really true. First of all, if the stuff gets wet it is probably ruined anyways, which is one of the reasons I don’t like it. Alex Wilson writes that " soaked cellulose will often slump, resulting in major voids and loss of insulating performance. Should be avoided in applications where moisture is a significant concern," which for me, is every wall north of Phoenix. Secondly, it would need a lot of water to wash away the boric acid. Thirdly, all kinds of insulations are flammable, which is why we protect them with drywall. And burning newspaper is not going to be as quick a killer as burning plastic foams. But Greg really doesn’t like it.
So while I agree with much of Greg’s complaint about cellulose, I am not yet convinced that mineral wool is the definitive answer; I remain confused. But I am certain that Greg has started what will be a lively discussion. Read it all at Greg La Vardera Architect
