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sinking cellulose


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In our area, we need R-30 in attics which is about 8.3" of cellulose. I am trying to get your opinions on whether or not you think that material keeps settling over time. I know it will but for how long and how low will it go in normal situations (ie, no huge amounts of moisture)?

For example, in a house that is say, 5 - 10 years old, I typically only find about 5-7". In houses that are 20 years, it is even thinner (generally).

A manufacturer (Cacoon) states that it will settle 1" after installation and that it needs to be installed at 9.3" for an R-30. How many new houses do you see with 9.3"?

My thinking is that paper that is continually exposed to moisture will continue to absorb it (and more readily than fiberglass) and will continue to get heavy and sink. And I am in NC where we have pretty humid months.

With the loss of "height" comes loss of R-value. If correct my theory tells me the R-value will diminish over time and will continue to until some level of max compression is reached.

?

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Hi,

Well, it does settle but I don't know exactly how much. It will only absorb just so much ambient moisture from the air and then it can't absorb any more. Does newsprint in North Carolina get heavier when stored on a shelf? Maybe a little but I'll bet it's negligible. Cells is very efficient at limiting air movement and becomes more so as it self-compacts so I think it's a wash. In the big picture of a home inspection, it really doesn't matter unless you're being paid to be an energy auditor.

ONE TEAM - ONE FIGHT!!!

Mike

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Having watched this in several homes, I agree with Mike in saying it's probably a wash within a few "r points".

Dense pack cellulose is really, really effective stuff; little to no air movement is a good thing. 8" of cellulose is much more effective than a comparable thickness of low density fiberglass.

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I concur. I remember reading a trade article some years ago, maybe in Fine Homebuilding, that stated the R-value was better in hard packed blown in Cellulose then it was in loose fill. Kind of the same reasoning as spray in foam, it stops a lot more air movement then fiberglass does.

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Back in my home town there used to be a guy named Sandy.

Sandy lived on a tiny patch of land out in the woods in the center of the Sharon, CT Audobon Society's game refuge. If memory serves, the land had been deeded to the Audobon Society and he'd been given the right to live there for the rest of his days.

Every day he would show up in Amenia and hang out in the coffee shop for hours or go up to the post office and sit on the steps with a couple of other old timers. He didn't work but he didn't beg and he always had money.

Nobody knew much about him. I remember going to visit him at his place one time. It was a little wooden shack about 8ft. wide by 10ft. long by 10ft. high. He had a kitchen of sorts made out of some old car fenders and stuff outside. He had a fire pit with some logs around it for a living room and there was a really old car, a Ford Model A, I believe, stripped and half buried in the dirt with vegetation growing up through it. There was a one-hole privvy about a hundred yards from the "cabin." I put it in quotes because if you'd seen it you wouldn't have believed that it was someone's dwelling.

What's this got to do with cellulose? Well, nothing maybe, except the "bedroom" was the cabin. When he opened the door it was packed from top to bottom with rolled-up newspapers. The door was lined with about a foot of newspapers and in the center, about four feet off the ground, was a long tubular opening 2-1/2 - 3ft. in diameter. It looked like a rustic version of one of those Japanese youth hostels.

That guy braved winters with 8ft. deep snow in sub-zero freezing temps in that cabin and never complained. I asked him, "Doesn't it get cold up here with the wind blowing in the winter. He answered that inside with the door closed it was like being buried a mile underground - dead silent - and he slept like a baby every night.

I assume he died years ago but I don't think I'll ever forget him explaining to me how newspaper, common cellulose, was a better insulator than the fiberglass my Dad was putting into the homes he was building.

ONE TEAM - ONE FIGHT!!!

Mike

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