Attic Insulation for Dummies

Strange as it may seem, we had a few leftovers from the "2-by-4 Week" we hosted last month — in which internet freelancers treated nominal 2-by lumber as if the dimensions were in feet instead of inches. That makes sense, though, because there are seven days in a week and we had almost 30 candidates... so here's another of them, compliments of the mother lode of stupidification of the internet, eHow: it's newbie David Miller¹ and his post, "How Thick is R30 Ceiling Insulation?" at HomeSteady.com.

That's information you can find in thousands if not millions of places around the internet. The answer, of course, depends on the insulating material. Miller, who claims a background in "the technology sector" (not the "construction sector," you'll notice) heads straight to rolled fiberglass insulation. That means he skips right past blown-in insulation, rigid panels, and the like. Moving right along, David informs his readers that

"R30 insulation measures 9.5 inches thick and comes in widths to accommodate 16-inch or 24-inch joist spacing. Most batts have a a [sic] light, corrugated backing board on one side for a vapor barrier." We were a bit confused by that "light, corrugated backing board on one side" crap, since fiberglass insulation typically comes in rolls, and that backing would be a little hard to roll up. No, what Miller meant was kraft paper, not "backing board" – the idiot. But why the "9.5 inches" thickness? David explains that blithely with this most excellent information:

"R30 insulation is used for attics and crawl spaces where 2-foot-by-10-foot joists are installed."

Say what? Don't you mean "inch" and not "foot" there? Of course you do... otherwise the house would collapse under the weight ceiling joists that weigh over 800 pounds per linear foot! Oh, and Dave? rafters aren't the same thing as joists – just so's you know...

Nope, Miller has zero idea what he's talking about; enough so he let some ignorant content editor insert "foot" into the dimensions of the joists without calling "bushwa!" He also misstates the thickness of R30 batts (they're 9 inches so they can lie in between joists 9¼" high). Add all that together, and it's no wonder David is our Dumbass of the Day awardee for today.

¹ The original ehow Article has been rewritten by a Leaf Group "contributor," although it's not a whole lot better. We got to it later... in the meantime, you can still read Miller's version using the Wayback machine at archive.org. Its URL was   ehow.com/facts_6124174_thick-r30-ceiling-insulation_.html

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DDIY - INSULATION