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Old 12-15-2011, 10:59 PM   #1
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Finishing my basement, vapor Barrier location for this application??


I wanted to ask this question before I get too far.

I'm located in Michigan.

I have a poured concrete basement in a 7 year old home that has not had any sign of water issue. I'm framing the walls with wood studs and plan to insulate with paper faced batts and then drywall.

Just for the heck of it, I waterproofed the entire basement wall with Drylok, but it probably wasn't necessary.

My question is where I should put the vapor barrier. I have about 30 feet of the walls framed so before I get too far i want to be sure I am doing this right.

A very experienced builder friend (40+ years experience) told me this but I want to get other views from other experienced people.

I'm building 2x4 stud walls, spaced about 1 inch from the concrete wall. Before putting the stud wall in place, I'm stapling a vapor barrier to the back of the stud wall. The barrier is NOT touching the concrete. It is stapled rather tightly to the stud wall, so that there is air space back there between the barrier and the concrete wall. After plumbing, electrical, etc are done I will then fill the cavities with paper faced batts of R-13 3 1/2" insulation, with the paper side facing me, then drywall over that.

Is this ok? I've looked around online and seen people securing vapor barriers directly to the concrete and been told it's wrong, and while what I'm doing is a bit different, I am still concerned and want to do this right.

Thanks.
Dave

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Old 12-15-2011, 11:05 PM   #2
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Finishing my basement, vapor Barrier location for this application??


Vap barrier ALWAYS goes on the warm side. This is for stopping condensation in the wrong spots.
Then mould etc.....

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Old 12-15-2011, 11:13 PM   #3
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Finishing my basement, vapor Barrier location for this application??


No plastic sheeting, or faced insulation below grade. No air space, fire-blocking required every 10' horizontally and at top plate to floor cavities above, Poly sill sealer under p.t. bottom plate for air/thermal/capillary break. Air seal the rims with foamboard first. The Driloc will send all water to wall/slab/footing joint. Air seal the drywall. You may not need the capillary break or p.t. plate if can prove to AHJ plastic installed at slab pour. http://www.buildingscience.com/docum...lation-systems
http://www.buildingscience.com/docum...-at-rim-joist/
http://www.greenbuildingadvisor.com/...-building-code
http://joneakes.com/jons-fixit-database/743
http://publicecodes.citation.com/ico...002_par031.htm
http://www.buildingscience.com/docum...wall-approach/

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Old 12-16-2011, 06:16 AM   #4
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Finishing my basement, vapor Barrier location for this application??


I'm just not sold what I'm doing is wrong. My vapor barriers are not sealed. They are stapled on to the back of the stud walls so they cannot be sealed. What is the point of a vapor barrier between the drywall and the paper faced insulation?

If condensation were to build up at all on either side of the vapor barrier and the barrier was between drywall and insulation, wouldn't that be problematic to the drywall, or get the insulation wet?

Maybe the best thing is to not have any plastic in there. I thought what I was doing was basically just keeping the insulation off the concrete wall JUST IN CASE any moisture ended up on the concrete, but I doubt it will happen anyway, so it was just an extra measure..????
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Old 12-16-2011, 07:05 AM   #5
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Finishing my basement, vapor Barrier location for this application??


I am pretty sure that a vapour bar is to stop condensation from inside the house. If it were to stop on the cold side, then you have water.

Seems odd to me as well.
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Old 12-16-2011, 08:48 AM   #6
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Finishing my basement, vapor Barrier location for this application??


Let me preface by saying I do not want to offend anyone. I'm not the expert, and that's whY I'm asking the questions. So, please nobody get offended if I question your advice. I'm just trying to make sense of it. I don't know how there can be many experts all having different viewpoints on the vapor barrier thing.

In my specific case, I'm not really sealing the vapor barrier on the back of my stud wall. It is more there to keep the insulation off the concrete wall.

Second, the scenario of boiling water in your house, and your windows condensate on the INSIDE...I understand that. But I don't think my basement will ever get that humid. It will be a temperature controlled environment by central air and forced heat furnace. So I wouldn't think there'd be such a swing in the temperature that I'd need to worry about condensation on the plastic.

Why is using paper faced insulation bad in a basement? I thought the paper was there to help secure it to the studs, and no other reason?

What is the point of a vapor barrier between drywall/stud wall?

In my specific case, my basement is built well, I have no leaks, the house is 7 years old so it has the newer technology used in construction. That styrofoam insulation is F'n expensive. My basement is `1900 sq ft and I'm finishing about 1700 of it. So, it seems pricy to go the foam route.

At any rate, can someone please let me know if it will hurt to put that barrier up oin the back of the stud wall like I'm doing? And if I should wrap another barrier around the front (between drywall/studS?) It seems that would be worse, as now my insulation doesn't breathe as much...maybe that's what you want? Completely encapsulate it? Although, it's likely SOMEWHERE there will be a hole or something missed so it's probably unrealistic to do that anyway.

I appreciate any help.

I just don't get how there are experts saying "put the barrier on the concrete wall" and then others saying "don't use one at all", then others saying "put it between drywall and studs"...I know it varies in different parts of the country and/or world, but it would be nice to get straight answers.
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Old 12-16-2011, 08:55 AM   #7
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Finishing my basement, vapor Barrier location for this application??


Plastic goes on the warm side of insulation for the following reason:

The warmer the air is, the more moisture it is able to hold. So, the warm, moist [presumably] air is on the finished side of the insulation. Without a vapor barrier, as this warm air (containing moisture) meets the cool air/concrete, it is going to cool off. Now, the air cannot hold as much moisture as the cooler air has a lower dewpoint and water precipitates out, getting things wet where the warm-cold junction occurs.

The point of the plastic vapor barrier is to prevent the warm air from carrying moisture to the cold air and making things wet. It's like weather, on a micro scale. No, you're not going to see it rain in the basement, and you likely wouldn't even have water droplets - but the science is still occurring, and giving mold a place to live.

If the vapor barrier were on the other side of the insulation, you would be trapping the moisture inside the insulation/studs instead of preventing it from getting there. It's VAPOR you are making a barrier against, not the concrete leaking or something. Your finished area of the basement is the source of the wetness, so to speak.
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Old 12-16-2011, 09:51 AM   #8
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Finishing my basement, vapor Barrier location for this application??


Why wouldn't the drywall act as a barrier then?

And, if you put the barrier between drywall and insulation (the warm side), wouldn't that then cause water problems in the drywall? Or, no, because there's presumably no cold air there?

If I add the extra barrier between drywall and studs, and then also put that plastic on the back of my stud wall, is this ok as well? I want to keep the insulation from touching the concrete wall and the plastic back there provides it. It's not sealed, since it's only stapled, so air can move around back there, which I thought was a good thing.

And, how does one attach a vapor barrier to the studs before putting drywall on? How do you keep that barrier perfectly sealed when you have outlets and such poking through? Seems it's never going to be air tight.
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Old 12-16-2011, 10:03 AM   #9
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Finishing my basement, vapor Barrier location for this application??


Drywall is not sealed like plastic. It does prevent some flow of air, but is not a barrier like plastic.

The drywall wouldn't be at issue because it is exposed in the room with warmer temperatures, where the moisture stays in the air. Plus, as you mentioned, it is protected from the cold wall by the insulation.

I just staple the barrier to the studs, then cover the seems/staples with tape. A tiny staple hole isn't going to let much air through if you miss one, but as long as you're doing it, might as well do it right. There are some self-sealing types of plastics too, but for their cost, I'd rather just use 6mil poly + tape. To go around outlets, there are more methods to seal that than this thread can hold. Ask Google for some examples.

As far as plastic on both sides, I've read that it's a no-no. Not sure as to the exact harm it will cause.
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Old 12-16-2011, 10:40 AM   #10
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Finishing my basement, vapor Barrier location for this application??


So what's the difference with a closed cell foam directly on the concrete wall instead of a vapor barrier stapled to the studs? I think using that foam right on the wall was suggested earlier or has been around the net.

Also, what's the difference between using 2mil and 6mil vapor barrier? 2mill is much cheaper. Will it get the job done?
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Old 12-16-2011, 10:46 AM   #11
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Finishing my basement, vapor Barrier location for this application??


Spray foam on the wall acts as a vapour barrier and insulator. That is...closed cell only.

When you do this, there is essentially NO transfer of warm, wet air from warm to cold.

No chance of condensation.
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Old 12-16-2011, 12:43 PM   #12
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Finishing my basement, vapor Barrier location for this application??


I'm more confused in some ways and clear in others, LOL. The explanations that have been given are great. Thank you to everyone. I just looked up a local city's building information because it happens to be online, and it says to put the vapor barrier on the warm side as well.

Ok so, if I do that, and put the barrier on the studs just before drywall goes on, then do I need to put anything against the concrete? I really hope I don't need that foam insulation on every inch of my concrete wall. That's a ton.

IS there a big risk to the batts of insulation that may happen to lay a little bit against the concrete (or not lay, but touch here and there)???
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Old 12-17-2011, 02:18 PM   #13
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Finishing my basement, vapor Barrier location for this application??


I have a friend who has a friend that's been a builder for many years, built his house for him, etc. I had him ask that guys' opinion. That guy's opinion is to not even use the vapor barrier, because either side you put it on the stud wall you run the risk of humidity, and if you put one on both sides of the stud wall then you can trap the humidity (i figured that much).

He said I should just avoid the vapor barrier altogether as long as I have no leaks, keep about 1 inch space between the concrete wall and the stud wall, and also paper faced batts are fine to use, and aren't a problem if they touch the concrete a little bit.

This is just another opinion.

I know we have codes, and I know they exist for standards, to keep us safe, etc, but they also always change and I am not confident they are always right either. I'm probably worried for nothing honestly, but I just want to do my basement correctly and not have a humidity problem. I'm torn on what to do.

Either way I think the vapor barrier on the stud wall side to the concrete is probably incorrect, so I'm gonna tear it out later, but I'm torn on whether to bother put one up on the warm side or just leave it out altogether.
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Old 12-17-2011, 03:52 PM   #14
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Finishing my basement, vapor Barrier location for this application??


Why bust your head thinking so much. The codes are right.
Go with it.
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Old 12-17-2011, 06:46 PM   #15
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Finishing my basement, vapor Barrier location for this application??


Codes are not always right. They update codes all the time, and what they were doing years ago they don't necessarily do anymore whether it be technology or what have you.

I prefer to follow the advice of those with a lot of experience, the problem is that in this case, there are experts that seem to say the opposite. Now explain that one LOL

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