OK to blow in about 9″ of cellulose over 1/2″ drywall?
16″ spacing on joists, span of about 14′ DW is all finished and painted.
Thanks.
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andyb
How dry will it stay? The sheetrock will hold the weight but not if the celluliose absorbs water..
should stay totally dry.
don't think dry weight would be an issue?
Andy
Should and will are different words.. I had cellulose in my attic and a perfect vapor barrier without leaks and every winter my insulation turned soggy. That caused my sheet rock to droop between rafters. Without the vapor barrier it would have wound up on my floor.
Cellulose absorbs moisture.. think of it as a giant paper towel.. soaking up moisture. I finally figured mine was getting wet from the vents in the soffits absorbing moisture from the atmosphere.
Now some here said that couldn't happen but when I tore my house down looking for a leak I never found a single flaw in the vapor barrier nor in the roof.
again with the BS.. give it up...
Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Mike Smith
So paper doesn't absorb water?
Frenchy, you have some hellacious water leak in your attic, best fix it.
Joe H
JoeH
Everybody claimed that and yet careful examination showed no such leaks.. I could go up into the attic during pouring rain and not detect a single leak.
In the same respect when I tore the roof off I checked carefully to ensure that I hadn't overlooked someplace in the vapor barrier which had allowed interior moisture to migrate into the attic.. I found no such entry point..
Can I introduce you to a new product, 'Ceiling Shellac'???
View Image
That will fix you up!
Jeff ;o)
"Can I introduce you to a new product, 'Ceiling Shellac'???"ROFL! my wife heard my guffaws from the other room.
BruceT
Frenchy, if cellulose was a sponge in the attic just waiting for winter, don't you think someone besides you would have noticed it?
How is it I don't see articles in FHB & JLC about the dangers of cells in your attic?
Give it up, you missed something in your house that was causing your problem.
Joe H
Thanks guys.
JoeH
I doubt it's possible for me to have missed something. If I went into that attic once I'll bet I went in a hundred times looking for any sign of dampness on the roof during some of the heaviest rainstorms we've ever had..
Besides the whole attic started to get damp in the late fall not just one area under a leak someplace. It did that before I'd actually start heating and always seemed to gain the most dampness during high humidity periods..
During the summer the celluliose dried out completely but starting in late october the celluliose was positively wet and remained wet all winter untill summer heat dried it out again.
IF I saw anyplace where the vapor barrier was somehow open, torn, or less than perfect I sure would admit that. After all I didn't build the old house and I saw many many flaws in design and construction (which is why I choose to tear it down rather than correct the flaws and remodel)
I suspect the reason it's not as noticeable to most is I doubt few homes actaully have as solid a vapor barrier as that house had. With a less than perfect vapor barrier heat will dry out the moisture that is absorbed and it won't become noticeable..
Now neither fiberglas nor celluliose retain their R rating when wet.
So even if this were a complete and total fabrication of facts, it's unavoidable. Some roofs leak.. Some roofs lack proper ventilation, and retain moisture escaping from a leak in a vapor barrier.
I suspect that most rotted roof decking is caused by that rather than by leaks thru the shingles and tar paper.
Don't know what the problem with your house was, but if all cellulose did this (which is your basic argument) there would be no cellulose.
Like many other building products that have come and gone, soggy cells would have vanished from the market place.
Joe H
"I suspect the reason it's not as noticeable to most is I doubt few homes actaully have as solid a vapor barrier as that house had. With a less than perfect vapor barrier heat will dry out the moisture that is absorbed and it won't become noticeable.."Now EXACTLY what was this "vapor barrier" and where was it located?From the ceiling staring with paint and then DW or plaster then explain exactly what was in each layer until you get to the sky.In most atticS you will NEVER SEE ANY VAPOR VARRIER..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 9/30/2008 1:08 pm by BillHartmann
Maybe the cellulose mfg was short on borate to treat the material, and they used calcium chloride.
ROAR!
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BillHartmann
Paint, 1/2 inch sheetrock, two layers of 7 mil poly taped at the seams. 12 inches of cellulose and the underside of the roof (1/2 inch plywood) 30# tarpaper and asphalt 3 tab shingles.(red) Roof pitch varied averaged about 10/12 pitch. shallowest part of the attic was about a 8/12 pitch
As I've repeatedly said crawling through the attic during the heaviest rainstorms we ever had yielded completely dry roof decking. No, absolutely no, roof leaks of any sort.
The soffit had continuos vents to allow air to flow through the attic and on out either through the roof vents in the middle or the 2 eve vents.
The 2 foot roof overhang prevented rain from entering the eve vents and I never felt any moisture during rain storms blowing in the roof vents.
The attic itself was chilly if it was cold or steamy hot if the rain occurred on a hot summer day.
what are eave vents?Soffit vents should be combined with ridge vents.Gable end vents are of lessor value but should not be mixed with the other two as that can cause some strange airflow problems.But I've never heard of Eave vents.
Is that what Adam's wife does when she gets frustrated with him?two things you don't cover in your description -What is the attic access and how was it sealed?what is the wall framing style of this portion of the house?I have seen cases where either of these two have caused MUCH moisture problem like you describe.
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Piffin
This house didn't have ridge vents. It was first built sometime around the turn of the last century. Ordinary stick framing but you should see how tight the growth rings on the 2x4's are.. makes your heart want to weep.. I can envision some 2000 year old giant being turned into mere 2x4's for construction.. Burlington Northern railroad was headquartered here and as you know they were an early pioneer into the western forests returning to the east with loads of lumber for construction..
I suspect most homes built here in the twin cites around the turn of the century were built with that wood.
Later when spurs went up north and we started to harvest the giant eastern white pine of the northern forests that became the more popular wood for construction, but this place is old growth douglas fir.. (I saved all I could to reuse)
Anyway
Gable end vents are frequently refered to as eve vents (since they sit right under the eve's) I suspect it's a local thing.. It had soffit vents on the south and north sides of the house and eve vents in the east and west gables.. Not to todays code but pretty standard stuff back then..
Attic access was pretty well sealed. It was a trap door that required the four corners to be loosened and then pushed up past the rubber seals. Since there was the same insulation on it as the rest of the attic as well as the same vapor barrier that wasn't a path (unless I had it open and was checking it out for rain).. (no nothing was stored there, too flimsey)
The insulation was dry as a popcorn fart during the summer even in heavy rains however late in the fall it started to get damp (even before we'd turn on the heat) by thanksgiving it was wet and stayed wet all winter long..
NO the gable ends weren't ballon framed. Nothing was. (I wish it had been. That would have been the reason and I could have fixed that) NO the drier went out the wall on the first floor. The waste stack was cast Iron and well sealed all the way up.. The furnace entered the fireplace flue as did the water heater. There was a copper/lead seal between the chimney and the rest of the ceiling and that was sealed down with some kind of black tar like substance which also sealed the vapor barrier.
I really looked carefull for any leaks in the vapor barrier.. that sort of thing would have been easy to fix.. (easy to spot too just look for a diurty area in the insulation)
Plus as I tore the house down I really looked for the source of the moisture..
I mean it makes sense.. that's where you'd expect it to come from.. that I could have dealt with.
Well then, if all that is true, you have one of those a-typical mystery houses that defies all normal experiences from all other sources and is therefore bad idea to base theories to apply to other homes from your experience.BTW, the vent confusion is apparently because you or your locality mis-uses the word eave. An eave and a gable are two distinctly different edges of a roofhttp://architecture.about.com/library/blgloss-eave.htmhttp://www.merriam-webster.com/dictionary/eave
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Piffin'
They've always been refered to as eve vents around here.. I was surprised when over a decade ago (has it been nearly two decades since I started reading Fine home building?)
I started to see them refered to as Gable end vents..
The rest of the world uses the right terminology.
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Piffin
I'm sure there are local differances everywhere.
"I suspect that most rotted roof decking is caused by that rather than by leaks thru the shingles and tar paper."After all I have torn off and the rot I haeve seen and traced, I can gaurantee it is not more than one out of a thousand if that much
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so the verdict is... frenchy is FOS ? and i worry about be'n rude...
:)
p
Strange. I've had cells in my 2nd floor ceiling, open to the otherwise uninsulated, unconditioned attic space, for about 10 years now, and it's been dry as toast since day 1. And there's no vapor barrier to speak of, since it's a retrofit to an 80-yr old house.
Mike HennessyPittsburgh, PA
Frenchy, did you ever figure out where all that water in your attic was coming from?
You might want to consider fixing the problem, whatever it is..............
Joe H
Is this a conventional attic or a cathedral ceiling?
If an attic, you're definitely without concern.
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
we blow 24" on 1/2" drywall... and Frenchy is FOS
Do you use regular 1/2" or is the ceiling board?There was a thread a few weeks back about what thickness GWB to use on ceilings- I didn't pipe up that we always use regular 1/2" with trusses @ 24" OC.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
typical ceiling would be trusses @ 24" oc
ceiling would be furred with 1x3 at 16" oc
GWB would be 1/2" Blueboard
we also use insulweb between the truss and the furring .. but that is so we can insulate before we boardMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
No problem at all.
Heck, go 12-14" Still no problem.
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Taunton University of Knowledge FHB Campus at Breaktime.
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