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I am starting to finish my basement. I want to use a good vapor barrier. Is house wrap such as Typar or Tyvek a good barrier to use on concrete walls prior to insulation?
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Tom the vapour barrier must go on after the insulation, just before the drywall, not behind the wall against the concrete!!!!
If you have moisture on the exterior concrete wall what you do is hang felt paper over the concrete, overlapping the side edges by 4 inches and let it hang down 4 inches FROM the floor level.(This allows the air to move behind the curtain)
Only fasten the top with staples to the nail plate under your floor joists.
This will prevent the moisture from migrating to the batt insulation.
If you use rigid insulation such as basemate you don't require anything behind the insulation.
Hope this helps
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Sorry Gabe but I beg to differ! What we do up here in Canada is, apply Tyvek or Typar writing side out against the concrete, frame, insulate, then 6 mil poly vapour barrier. It amounts to the same thing as above ground work. It costs a little more but in my opinion gives a superior job. Just another opinion though!
SteveM
*Sorry Gabe but I beg to differ! What we do up here in Canada is, apply Tyvek or Typar writing side out against the concrete, frame, insulate, then 6 mil poly vapour barrier. It amounts to the same thing as above ground work. It costs a little more but in my opinion gives a superior job. Just another opinion though!SteveM
*Sorry Gabe but I beg to differ! What we do up here in Canada is, apply Tyvek or Typar writing side out against the concrete, frame, insulate, then 6 mil poly vapour barrier. It amounts to the same thing as above ground work. It costs a little more but in my opinion gives a superior job. Just another opinion though!SteveM
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In a country such as ours Tyvek does not allow the evaporation of moisture due to the sudden and dramatic temperature changes that occur over a few hours. It is not uncommon to have a 20 C change in the matter of 8 hours.
The curtain as described will allow for the evaporation to occur easier.
The Tyvek on the outside of a conventional home application, acts in harmony with the curtain wall pricipal.
Your siding on the outside, brick, vinyl, wood, all have some type of air or water release built in. ie; weep holes etc. There also is a flashing at the base to redirect water and allow it to drain away from the house structure. A basement wall does not have that luxury.
A healthy house is one that is allowed to breath.
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I think the whole question hinges upon where you live. In Canada the vapour barrier goes on the warm side of the insulation and a moisture barrier (to keep the insulation dry lest you get water infiltration through the concrete walls) goes between the concrete and the insulation. This does not need to go all the way to the joists, merely from grade level to the floor (and preferably under the bottom plate).
In warm climates, I think there is a different approach (if not, there should be).
That should get some interesting responses!!!
*According to articles I've read, housewraps such as Tyvek are air barriers not vapor barriers. They are intended to stop air movement not moisture. Placed on the outside of a house, they "breathe" allowing any moisture in the wall to pass through and not be trapped. I don't see a use for them in a basement. FHB #88 has a good article titled "Air and Vapor Barriers" Dave L.
*the basement that i am addressing is new however it is block. does it make any differance?
*I would like to clarify what I said and apologise for the multiple postings of the same thing. How does that happen anyways.My method for basements is to first apply Tyvek, writing side facing the concrete. Framing is next and sits on top of the Tyvek which now wraps up on to the inside of the framing. Next is insulation and finally vapour barrier. Vapour barrier is caulked to the Tyvek. This system closes off the inside of the wall cavity, where the insulaion is alomost 100 percent. Just so yopu know, on additions, we run Tyvek under the bottom plate so we can tie it in with the inside tyvek in the basement. All of this assumes that Tyvek does what it is supposed to do. MY UNDERSTANDING is that it will allow moisture and air to pass from the inside to the outside but not the other way. If this is true, then my system works. If I am ill-informed then my system is worthless. I am anxious to hear some response to this. I will also be attending a local course on Tyvek this week and will raise the subject. I will post what I learn.SteveM
*Steve, thank you for your responce. I am however, unclear of what you mean when you say that the vapour barrier is caulked to the typar or tyvek. Could you be more specific. Thank you.
*This home is in Indiana. So do we do it like the Canadians?
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Tom, you're question asked if Typar or Tyvek is a good MOISTURE BARRIER.NO!!!!Modern day housewraps are not and were not intended to be a water or vapor barrier.They are actually called AIR INFILTRATION BARRIERS.AT least in my area they are called that.I see it as a waste of money by putting it in your basement.There is no air infiltration down there!!
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So.... now with the seminar under my belt, I have learned that my method is sound. Tyvek is not only acceptable but probably superior as a MOISTURE barrier, not to be confused with a VAPOUR barrier. And yes, it is to be done as I described. Thanks for laughing Adirondack, I never take all this too seiously. Just an exchange of idea's. I was recieving e-mail from Gabe, who's idea's are different than mine as you know. He sure made me think. But until someone has hard proof that Tyvek causes a problem I will continue to use it on basements. For me, it's faster and more efficient.
SteveM
*Thank you Steve.
*I am from Canada and I've never hear of Typar in a basement application.These products are made to stop the flow of air, no the flow of moister. They are one directional, meaning they allow air movement out but not in to a certain degree.The felt paper is the only way as far as I am concerned. Another tip in cold climates is to leave the insulation up 8" to a foot to allow air flow between the concrete and the insulation.This helps to keep frost form traveling down the wall too.There isn't much heat lose with this method, because the ground below the frost line generally stays around 65 degrees C.
*A moisture barrier is generally a vapor barrier. Actually, the are only moisture/vapor resistant. They do not totally prevent the passage of air or water vapor (they have perm ratings of 1 to 5).Canadian/Alaskan exterior walls are built very different than in the lower 48. The difference is where you locate the freezing point in the wall. (the outside of the wall will be say 30 below zero and the inside will be 65 - non celcius). If you place the insulation close to the exterior of the wall, you move the freezing point close to the exteior, and via versa. The freezing point is critical because it controls were ice forms in the wall. (you have to deal with ice expansion and liquid water when it melts). (this is why the previous message suggested that one leave an 8 inch insulation gap at the bottom of the wall.) For the US types, there is a fun little book called 'building a house for alaskan conditions' put out by Univ of Fairbanks. Very basic but very informative.Because a basement is below ground. The temperature differentials will be much different. Near the top of the basement (near the ground surface) the temperatures on the outside of the basement wall will be below freezing (I assume you have not dug a basement in perma-frost), but at the floor (8 feet down) the temperature will be between 35 and 50 degrees (caused by the geothermal gradient)You have two factors to consider. A) control the water (liquid or vapor) before it gets into the wall or B) control it after it penetrates the wall. The other factor is that the movement of water vapor through a wall is controlled by temperature and water vapor partial pressure differentials. These can vary during the year, and you can have a situation where temperature changes alone can cause water to be drawn into a house during the summer, and driven out during the winter.I prefer to do A, but sometimes you have to do B. For exterior control, use material like tar, bithuane (misspelled), and similar products. Also put good drainage around the exterior of the all of the walls. The majority of the above comments are about controlling the water after it has pentrated the wall. The only problem with attaching a water resistant layer directly to the interior of a wall (with no provision for evaporation) is that the water will build up inside the wall. The water will not remain static. Instead, it will flow to the bottom of the wall and go into the slab where it will then enter the room. This water movement generall occurs under unsaturated conditions. However, you can have localized water ponding in the floor. It is best to keep water out of a wall. It can be difficult to control it once it has enter a wall.
*Steve,Will you please explain what the seminar presenters said the difference is between a moisture barrier and a vapour barrier (I hear the new term is retarder). What is vapour if not moisture? Are they trying to say that Tyvek stops the "big stuff" (rain) but not vapour. If this is the case, and given it's perm rating, it sounds like an air barrier to me. I don't see its usefulness in a basement to stop airflow and "big stuff". Isn't it vapour that you are dealing with down there?
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Steve, Fred,
Steve, I think your system of house-wrap next to your concrete walls and under the plate
should work well...but not necessarily for the reasons you think it works.
1- Its a retarder to air blowing past any leaks that you may cover with it if you cover leaks well, ala acoustic
sealing caulks, no holes, seams, etc. (Doing a perfect job)
2- I don't like trapping water and having green stuff grow, so I think because it does
let gases such as water vapor diffuse through it in either direction the partial pressures
draw it, then that's not hurting you either.
3-Wet basements and air leaky basements, and cold basements are not so
good, and I think house-wrap and poly will not take care of wet basement problems directly. What I'm saying is that
if the basement does not have any major water
problems, during the entire year, then your
house-wrap will be fine.
4-The "writing side" unidirectional-ness
of house-wraps other than Tyvek may make a
difference if they are made with
micro punched holes that close under pressure? Or
ten years hence it may be found out to be just "pump up the sales" silliness.
Steve, get us the scientific literature
on this from one of your favorite put it up writing to the concrete and post it
here or give us a link. Thanks. I will take a peak on the web also.
Fred....Tell us your cellar methods,
Jack : ()
*As you can see by the confusion between all the parties, it's understandable that even Architects don't know the difference between air barriers, moisture barriers, vapour barriers.And until someone can properly define them I quess we'll have to rely on this simple test.All of you who don't think Tyvek is a water barrier, hold a piece in front of your lips and spit through it.All of you who don't think Tyvek is an air barrier, hold a piece over your heads and tie a string around the neck portion and try to breath through it.What your estate will discover is that it doesn't do so fast enough to be of any help to you.What you will find is that eventually, water and air can penetrate Tyvek. The question is will it so so before damage is done.Anytime you seal wood with trapped moisture you will have dryrot damage. Sometimes it will be negligeable othertimes it will be disastrous.It would be nice if it was an exact science but it isn't. There are too many variables.Even between two solid walls, there are convection currents. There is humitity. There is mold and mildew.Do we let the walls breath or do we build an incubator and wait for damage.
*Gabe,Yes yes yes...but it is "wet-rot"is not "dryrot"...nothing rots "dry"...it is, sometimes, dry, later, when found in a"destroyed state" after the "wet state" has done it's thing....Wetly,Jack : )
*I belive fredl is closest to the truth. Remember, this started with finishing an existing basement. When you stud out the walls you are not going to have a solid top plate configuration. Air will have plenty of room to move out of the stud bays (providing it rises as in warm air). I've always set my wall out 1" from the block to avoid concrete contact (now code in my area). If I do have to place wood on the wall such as furring out a stair, I use treated (again code, concrete contact). I have been draping plastic over the block or poured walls in the 1" space between the framing and basement wall. The single purpose of this plastic (even saran wrap would work) is to prevent moisture from the wall contacting the framing or insulation. The plastic is stapled every couple feet and the draping leaves some space for air movement. If any moisture does follow the plastic down, the wood itcomes in contact with is the treated sole plate. I hope this helps answer the question.
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re Typar, Barricade, Tyvek, etc. As building
wraps, these products when properly applied over STUDS (taped seams, correct overlaps, etc) will
mitigate air and moisture infiltration until they
expire from the elements. When you install siding,
the fasteners will perforate the wrap, and as the
wraps are not self sealing, you have potential for
leaks from wind driven rain or from capillary
attraction. This is why the UBC requires rated
asphalt paper, or APA rated structural sheating, or APA rated structural sheating and asphalt paper as acceptable forms of moisture barriers.
Since APA rated sheating is a barrier which will not allow moisture to travel through it and the
fact that type I sheating has no time limit for
exposure to weather, you now know what we have known since building wraps' inception------
it sure serves no purpose but is costly.
Thanks
*re Typar, Barricade, Tyvek, etc. As buildingwraps, these products when properly applied over STUDS (taped seams, correct overlaps, etc) willmitigate air and moisture infiltration until theyexpire from the elements. When you install siding,the fasteners will perforate the wrap, and as thewraps are not self sealing, you have potential forleaks from wind driven rain or from capillaryattraction. This is why the UBC requires ratedasphalt paper, or APA rated structural sheating, or APA rated structural sheating and asphalt paper as acceptable forms of moisture barriers. Since APA rated sheating is a barrier which will not allow moisture to travel through it and thefact that type I sheating has no time limit forexposure to weather, you now know what we have known since building wraps' inception------it sure serves no purpose but is costly.Thanks
*Well, I think I'M gonna wet myself, as so well stated by Adirandack Jack. We could all argue this to death but I'm not prepared to do that. I am however gonna ask a representative of Tyvek to read through all this crap we have all written and straighten us all out. I have no doubt that there are some people on here who would argue with engineer's, professors, etc. Common sense says that we must differ to those who have expertise beyond our own. Let's hope that we will get a response from some people more learned than us. Question is 'how will we know when they have posted a response'? SteveM
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I am starting to finish my basement. I want to use a good vapor barrier. Is house wrap such as Typar or Tyvek a good barrier to use on concrete walls prior to insulation?