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The Typar will allow water vapor to pass through. Your batts will wick up that moisture. Staple 2 sided aluminum foil to the sill plate. This will also reflect heat back to the room. Or use the 2 sided aluminum “bubblewrap” that claims R5.3 when used on walls. It is onlt a half inch thick. It claims R15 when used on floors. GB
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The Typar will allow water vapor to pass through. Your batts will wick up that moisture. Staple 2 sided aluminum foil to the sill plate. This will also reflect heat back to the room. Or use the 2 sided aluminum "bubblewrap" that claims R5.3 when used on walls. It is onlt a half inch thick. It claims R15 when used on floors. GB
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I'm surprized FredL hasn't weighed in on this one.
My thought on this subject is that if water has already made its way thru the concrete foundation wall the most desirable consequence would be for said moisture to become energized (vaporized) and thus make its way out of the basement vertically. Otherwise, it's gonna accumulate near the plate on the basement floor. If on the otherhand, we're talking about preventing water vapor, which has entered the basement thru other than the walls, from condensing on the cool walls then it would seem like a great idea to employ a moisture barrier...and my vote would be for tar paper tacked securely to the out side of the wall framing. I'll bet tar paper would be a strong enough of a membrane to withstand the pressures involved in the installation of blown-in cellulose....maybe some extra furring might be necessary. Anyone have thoughts on this?
Brian
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There was a very heated discussion about this very subject about two months ago here on breaktime. I have since taken a certification course from Tyvek on air barriers. At the course I raised this very issue about using Tyvek as a moisture barrier and was informed that it is in fact an excellent moisture barrier in this type of situation. You must install it with the writing against the concrete and wrap it under the wall so you can tie it in with the vapour barrier. I've been doing it for about three yrs now. My feeling is that it does all the things you want it to do. It is designed to keep moisture out yet lets trapped moisture in the wall cavity escape. It is continuous. Tar paper is FULL of holes. It is the Cadillac solution to MOISTURE. However if you had water penetration I cannot imagine tar paper doing a better job than Tyvek not that either one was ever expected to keep water out. If you want additional back up info contact me and I will give you the e-mail address of the man who put on the course. He will no doubt convince even the most skeptical tradesman.
SteveM
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steve,
The "Diode effect" moisture man...Please email how scientifically moisture knows which side of tyvek has writing.
Far from the stream,
J
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Jack,
I'm not an engineer or a scientist. Like all of us we must use the products as per manufacturers specs. When you put shingles on a roof I'm guessing you put the stone side up becase it makes sense. When you put Tyvek on I'll bet you put the writing facing out. Why do you do that? Because that is the way it works. My understanding of this product is that moisture passes only one way through it, from the non writing side to the writing side. If I'm wrong on this point my theory is very flawed, however, the manufacturer's representative stated clearly that the use of it's product as moisture barrier as explained in my former posting is not only appropriate but far superior to tar paper. They have a large R&D department that could make the whole bunch of us look like fools. Who should I believe?
SteveM
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Steve,
Often one has to play "follow the leader" in life I guess...like when one of Americas ace aerobatic stunt teams during practice augered into the desert all wingtip to wingtip following "the lead man", an expert on a "wrong path."
Have your people email my people in regard to your famous "diode wrap."
Way far from the stream, not drinking the "Kool Aide."
J
*It won't work unless the writing faces out? "Pay no attention to that man behind the curtain"The first time I read the instructions telling me the label had to be facing out, I threw the roll away, and haven't used it again since.This is pure Madison Avenue!Jon
*All those in the know as to how the "writing on the wrapper" controls the "diode effect" of housewrap...please by all means chime in here and enlighten us all once and for all...Steve...Get your man to join in here.Near the stream,J
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I'm sorry I ever responded. I'll keep my mouth shut from now on!!!
SteveM
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Steve,
No need to not sound so silly...but if you are going to hang yourself so far out to dry atleast bring in some reasoning other than a company PR guy says so...
Waiting for the science, near the stream,
J
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I've taken the course on the proper use of the product Jack. Have you?
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Steve,
No and I can't believe you did either...Like I said, just show me the holes in His wrist and I'll believe...Until then I feel you're a well trained PR assistant...I've said enoough...no harm meant...good luck.
On top of the stream,
J
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Did someone mention "cold wall"? Which wall will be colder? Is the outside wall insulated? Is it covered with dilute asphalt? sprayed on membrane? How about the footing? Is the drain tile in place? does it work properly? Is the slab insulated? moisture retarder used under the slab? How much? How much water product is being introduced into the structure? Experiencing any moisture problems in any part of the house? New house? Old house? Tight house? Will the ceiling be insulated as well? Heated basement? Is the basement living space? What does your nose tell you about the basement? Any spores? Thanks for opening this subject up. Never were there so many experts. Let's see what the current thinking is on this. Great question. Thanks GB
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doing a test, rudimentry but a test nonetheless -
taped a square of Typar over the top of 2 three gallon pails with a hollow in middle big enough to hold about a gallon of water.
one pail - writing up
other pail - writing down
poured a gallon of water into each...waiting in anticipation
*We used the Typar, the building inspector liked the idea... I thought the side with the writing on it was just more weather-resistant... Typar will let moisture out if it gets in...
*Results are in - writing side up - virtually all water passed through into pailwriting side down - held waternow let's just say, for the sake of argument, that there were no pin pricks or holes in either one - and agreeing that further testing would be needed to cooberate these findings - what could we conclude from this single test?
*Young Bob,Now that is interesting. It is the exact opposite of what I would think should happen. As a housewrap, installed writing side out, it lets the water in!Anybody else doing this experiment?Rich Beckman
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I built a large garage five years ago useing typar and tyvec, both let in rain and held it for days . Printing was facing out my plywood got soaked.
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Here's the kicker. This AM I go out to the shop and the writing up one had completely drained into the pail. (the other had allowed maybe 1/4 through) I got my wife and youngest hoopster to verify the results as wittnesses and dumped them both out, and gave it another thought.
I am thinking there is maybe a defect (hole or tear) in the writing-up one and in all conscience cannot stop here and so;
Typar test redux:
took same pieces of typar from first test and REVERSED them, that's right, I turned them both over. In all fairness have to wait until around 7:30 pm PST as that's when I checked yesterday but I gotta tell ya sports fans, it doesn't look good for Typar.
gotta eat - yb
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I swore to myself I would not come back to this discussion but here I am. Well done yb. You took the bull by the horns and did some testing. Even if it proves nothing, you were interested enough to look into it. Now that's what breaktime SHOULD be about. Thanks for renewing my faith!!!!
SteveM
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inconclusive results this PM - will check in AM and report. It really does look like the writing up pail is letting more through, but I want to wait, strip the tape, and make sure. This is kind of hard to believe, isn't it? - yb
*Results are in redux;writing side down - approx 1/4 water went through into pailwriting side up - approx 3/4 water went through into pailI sure hope someone else trys this and comes up with more test ideas. This seems like it must be an aberation, I hope so at least. - yb
*Gentlemen. There are too many contradictions and unsupported statements being made. Jack picked up the diode bit--SteveM didn't say diode but he did say it (Tyvek) lets out moisture but also prevents the entrance of moisture. DuPont claims that TYVEK's perm rating has been lowered so it is now a moisture barrier[sic). Yet any builder in the wet southeastern USA is asking for a law suit if he uses TYVEK over OSB of plywood sheathing.Question. If one already has a capillary break on the foundation's exterior--dampproofing--why does one now want another moisture barrier [sic] on the interior? GeneL.
*Gene, You're absolutely right, the basement wall should be dry. Frost might form on the cold wall behind the insulation if the vapour barrier isn't airtight, but the same thing would occur on the upper floors as well behind the plywood, yet no "moisture barrier" is required there... the bottom line is, around here, somebody wrote it into the building code that there has to be a moisture barrier behind the insulation below grade... but NOT where the foundation is above grade, so any moisture in the wall can migrate out through the concrete (so that shoots down the frost theory, doesn't it....). Don't ask me where they got their logic from, it makes no sense, since there also has to be "damproofing" on the outside.... I don't write the codes, I just have to follow them :) Personally, I'm not a great believer of using batt insulation below grade, expanded polystyrene costs marginally more but probably on a per R-value basis is around the same (anyone calculate this?). Then no "moisture barrier" is required, and you can avoid all that framing and just use Z-channel or a similar system.Ross
*Ross, SteveM and others. I first learned of Tyvek in the early 1970s from Bob Hoppe then of Brookhaven National Laboratory. It was to be or was marketed by Owens/Crning for use in attics over the insulation. I was one of the very fist in New England to ue it and introduced it to Sonoma County, Californai. We are told that everything good, or kinky originates in Californai. Yet builders there never heard of it in 1980.SteveM's comment seems contradictory, or is it because the polysemous word moisture has more than one meaning? I was puzzled by his comment that at a TYVEK seminar--do we assume a TYVEK seminar is hosted by DuPont?--he was told that the printed side of the Tyvek must go against the foundation wall. In all these years I never heard or read that which side was out made any difference. Recognizing I'm not error free, I called DuPont and spoke to Theresa Weston. I quoted verbatim SteveM's post. She told me that Tyvek is not a diode or a one way valve. DuPont never said or says where the printed side goes...it make no difference. Our only disagreement is that she insists that Tyvek is a water barrier. I told her the perm rasting is too high. Ross. Some one ought to ask the code officials who will be responsible if damage results with two vapor barriers[sic}: one on the exterior of the foundation and the other on the interior. The solution then, is as you suggest. Use permeable EPS glued to the foundation wall.The problem with this is that it really doesnt eliminate the framing unless you use Surface Mounted Wiring (SMW). Furthermore, there is the additional problem of how much wall insulation is required by code.In New Hampshire, for example, when converting a basement to habitable space, the foundation walls must be insulated to the same R-value as the above grade walls: R-18.That would require 4-1/2 inches of EPS.GeneL.
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Thinking of using Typar instead of the old standard tar paper as an inside moisture barrier on concrete foundation walls, before framing out the wall and insulating. I don't see any reason why Typar wouldn't work just as well, with the advantage that I just have to staple it along the sill plate and let it hang rather than concrete nail three rows of tar paper on the wall... anyone think this is a good / bad idea? (and no, I don't want to attach the tar paper to the frame wall before I stand it up, we leave enough room for an R-20 batt in a 2x4 wall by spacing the framing out 2" away from the concrete).
*I dont believe Typar is a moisture barrier. Its a wind barrier. 15 lb tar paper isnt a mb either. 30 lb and up is though. Read that in FHB a few years back.