Sippican Cottage

batt insulation


A Man Who Has Nothing In Particular To Recommend Him Discusses All Sorts of Subjects at Random as Though He Knew Everything

Sippican the Blowhard

You know, I figgered this insulation racket all out before I began. I crunched numbers. I did enough research to get a fellowship. I was the Sippican Division of Weights and Measures for a solid month. Then I crumpled up the half a sheet of paper with the numbers on it and threw it away. I immediately forgot everything I’d discovered, because my mind is kind. I’d made up my mind what to do, and how to do it. Why remember how I got here?

Oh, yes, I’m trying to explain my thought process to the internet, which is like being on trial in front of a short bus convocation of the Doges of Venice. No one takes your word for anything. Citation please, is the first comment on anything you write, and the please is a lie. I’m supposed to find some article in a newspaper that lies about every other subject, but is no doubt right on the money about this one, so use it for a citation. Well, I ain’t gonna.

I will offer a couple of observations, however. First, cellulose makes for good, cheap, fairly easy to handle insulation. It’s just ground up newsprint and packaging cardboard, treated with some sort of borate that makes it non-tasty for bugs and keeps it from burning. No, really, it’s paper, but it absolutely won’t burn.

As usual, there’s maybe four minutes of information spread over sixteen minutes of that video, but who am I to quibble? I’ve written about 125,000 words about fixing my house in the last three months, and it’s still not insulated. Mr Hockey Forward Haircut in the video lays a penny on the cellulose and blasts it with a torch until it’s molten, and it barely scorches the insulation. I hope the dude had an IQ over 125 before he started, because he’s bound to shed about 25 points after breathing the fumes from the burning foam stuff.

You can find any number of internet wags that will tell you that, yeah, sure, but after it gets wet, the fireproofing leaches out. I’m an internet wag, and I’m all wet, but I can assure you it’s not true. The borate doesn’t leach out. It’s really not toxic to humans, either. Fairly benign stuff in the scheme of things.

So cellulose is cheap, and it’s safe, and it’s more or less easy to install. What’s the catch? Well, the foam fellers will tell you that it’s worth it to pay 12 times as much for their product, because of air infiltration. Foam seals everything up. Air passes through loose-fill insulation. Case closed, they say.

Not so fast. If you just blast loose-fill insulation into your attic into a thick, fluffy blanket over the ceiling downstairs, some air will pass through it, it’s true. But we’re not going to loose-fill anything. We’re going to densely pack the cellulose, and dense-packed cellulose is a pretty efficient air barrier. It’s not like a sheet of plastic or anything, but it’s miles better than fiberglass batts, and close enough to foam to forget the difference. The key is how to densely pack it.

Dense-packed cellulose insulation has a pretty easy definition. You have to achieve between 3-1/2-lb. to 4-lb. per-cu.-ft. density. You can figure out if you’ve got enough pressure and technique by trying an area, then wrecking your work, and then weighing how much insulation falls out. No thanks. You can decipher the chart on the bales of insulation to figure it out. The maximum coverage per bag by wall or ceiling cavity depth works pretty well. Helps you to purchase the right amount, which you never do no matter how much measuring you do. Here’s a pretty good explanation of what’s going on from a manufacturer of the stuff:

Regular reader and commenter Mike Anderson pointed out a Fine Homebuilding article that lays out dense-packed insulation techniques pretty well. The pictures are a lot better than anything you’ll ever see on this blog. Of course the author, an insulation contractor, has to say:

Don’t try this at home

Although some DIYer’s claim success dense-packing cellulose with rental machines from home centers, these low-pressure machines make the process very slow and achieving a density sufficient to resist settling is difficult. The process is best left to
a specialty subcontractor with a more powerful insulation blower.

This is called begging the question. Who says I’m going to use the rental machine at the home center to do it? I ain’t. And I’m not going to buy a $20,000 contractor-grade blower, and buy a truck to install it in, either. I’m not going to hire anyone to do the work. I’m going to use a leaf blower.

[To be continued]

4 Responses

  1. “Don’t try this at home.” Clearly, this is the 21st century version of “I dirty double-dog dare you.”

    ” I’m not going to hire anyone to do the work. I’m going to use a leaf blower.”

    I await the next installment filled with great anticipation and amusement. I recall telling my wife, just a couple months ago, “I’ll just sand all those stains and weathering off that back fence before staining it. Should just take a weekend.” I finally finished last week, when the Sun stopped trying to kill me.

    (Oh, and thanks for the shout out. Now I’m down to 14 minutes of fame in my future.)

  2. Why do I feel like it is going to have something to do with the wife’s vacuum cleaner–the one that used to have a nice long hose? Didn’t I read somewhere that it was possible for some whiz guy to reverse the direction of the suction from intake to blow out? A leaf blower–how heavy is that thing?

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