Insulation, Radiant and Vapor Barriers - I am Finishing a Basement - Vapor Barrier Question for Foundation Walls

Hello,

I have a vapor barrier question for foundation walls in central Michigan (if it makes a difference)?

The basement has half grade fully across the south side. Full grade on the north. ...and sloped grade on east and west sides (easy to visualize, right?). Majority of walls are on south side with (2) 8'x4' glass block fixed windows on south side evenly spaced.

I have been doing some research on the proper way to insulate basement walls during basement finishing.

I have heard:

1. Pro: Apply vapor barrier on cement wall to prevent moisture from cement wall entering stud wall and insulation. The Con: moisture can be trapped between barrier and foundation wall causing mold, etc on foundation wall (saw pictures).

2. Pro: Apply vapor barrier on face of stud wall after insulation is installed to prevent moisture from penetrating dry wall from cold side. Con: moisture from cold side will stop before drywall...but will mold up insulation cavity if it condenses.

3. Pro: Apply to Cold or Warm side, but not both. Con: Do not apply vapor barrier to both warm and cold side simultaneously since interior moisture from inside house will penetrate through drywall and barrier (through elec switches and receptacles) and be trapped in between barriers when it condenses with cold wall.

4. One of the "Latest and Greatest" Pro: Apply 2" XPS (R-10) to foundation wall with some sort of adhesive. Install stud wall. Do electric, plumb, etc. Install insulation (optional), then drywall (No Poly anywhere). Con: very expensive, but no moisture problem since cold side is completely insulated from stud wall and drywall.

Any tips on these theories, myths, or facts? I would just like the proper way to do it so I can have a clear conscience. ...Plus, I can't afford option 4 anyway, which is about 3-4x more $. I appreciate any help soon on this matter, since my materials are taking up garage space ;o)

Thank you very much!

Here in Mo we hang a 6 mil poly on the wall from the sill plate. Build stud wall.P/T plate on the bottom. A, R 13 paper to the room side in the studs then a 4 mil poly over that. Then the drywall or panel. A block of R19 up in each joist space all around the home

hey scooter ...I am a framer and my general rule is any part of the wall that will be BELOW grade, just poly the wall after insulation. If you are worried about moisture make sure you inspect all your walls carefully before studding in the new ones. address any cracks or peeling before and you should be ok. and one more thing... any new wall that may attach to a existing EXTERIOR wall needs ploy between the walls or you could have a cold spot...and possibly a moisture problem there. Hope that helps.

http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic=11810

http://www.ornl.gov/sci/roofs+walls/facts/index.htm

The two sites provide on the issues concerning moisture and the applications used to address such issues. Oak Ridge National Laboratory (ornl) is the agency the developed the first atomic bomb. You might find their information a little dry but their thoroughness and statistic collection is beyond reproach.

If you read through some of this information, you will notice the it explicitly implies that "Site conditions determine the appropriate course of action." For example; if the soil in your area contained a good deal of clay providing a moisture barrier directly to the foundation wall would be appropriate. Having sandy soil, it would not be appropriate. Other factors would be site grading, roof drainage systems, climate conditions, etc.

If we couple these factors with different schools of thought over appropriate applications, it is not surprising that we hear conflicting applications and their impending doom if we do not follow their application. While one school believes in the dominance of "Water Shedding Systems", which I belong to, the other school seek to minimize it. Both schools turn to "Psychrometric Charts" to support their findings on the integrity of the structure itself, which is not debatable. While this falls under the "Health and Well-Being of the Occupants", MOLD would fall under the same category. Though structural collapse is highly unlikely with Mold, condemning of the structure is not unheard of. Which brings us to the center of this debate "Sick Building Syndrome (SBS)". This involves primarily High Rise Structures and for some reason it has been extended to residential. Though Mold is involved in both types of structures, the determining factors are immensely different. This is like comparing apples to oranges. Without question, this is an over-simplification of this issue. I have been proven wrong on several occasions concerning particular aspects of this issue. Yet my position on this issue remains unchanged, regardless of the discourse and humiliation that followed.

I wrote this in an attempt to explain why we see and hear conflicting applications with basement finishing. It does in no way suggests that other suggested applications are wrong. However, it may or may not be appropriate for your "Site Conditions".

As far as finishing off your basement, my advice to you would be for you to seek the advice of your local building officials. Not only are they experienced in this application but they are familiar with "Site Conditions" which will influence their recommendations to you.

Francis R. Lazaro
Energy Conservationist
State of New Jersey

Thanks for the replies, Ed, Moose and Resercon.

Resercon, I'm at work now and no chance to peak at the sites yet, but will these websites give me detail of how to apply construction (vapor barrier/insulation) technique for my particular (or similar) area. Or should I try to look for some subs in the area with new construction and see if any finish basements are being performed. But, the method to use.

I have a buddy of mine that has been doing the 6mil on foundation wall, then install wall paperback insulation and then drywall... but he has been applying that method for years and probably doesn't really keep up with the latest standards that have been popping up the past 10 years or so. Any input? Or anyone elses feedback is welcome. Thanks

Scott

The "new" developements and "revolutionary methods" to finish off a basement keep popping up (actually, the same ones on a 10 to 15 years cycle).

scooterpop - You have 3 different walls with different external conditions and want to do a pro and con on each of them with a number of different finishing/insulation/moisture/vapor control systems?

To start with, make sure all above ground moisture conditions are properly satisfied so you have a reliable condition to design for.

You obviously do not need (and may not want) the same amount amount of insulation on the full basement wall.

Do not try to over-analyze a basement system if you want to maintain your sanity. Use the proven methods for your area (climate and soil conditions)!!

After you are happy with the method you have selected, do not relax since you still have the floor to worry about, which has similar temperature to the bottom half of the walls, but more available moisture and probably more square footage. - The battle never ends.

Dick

Thanks for the replies. I don't want to apply different systems, but what I wrote above was giving all the different methods that I have researched that are being applied. But it seems that no matter which one you choose, they all contradict each other with someone (or web site) elses link to research studies, etc. I was hoping that someone who was familiar with my geography would be able to shed some light to what method is good for me. I'm not trying to be lazy about it... it's just that I'm a fairly straight thinker, I guess. Tell me where I can get the answer (hopefully without the hoops). Building it is no rocket science, but how it's put together is where all the masterminding comes in... with facts to back it up, of course.

I'm not really sure which way to persue with the varieties that everyone speaks of even for my area. I explained the Cons of the methods that some have given me already... but obviously seems to be the norm for their experience and geography. I looked at the sites given to me above and it seems fairly general, but not specific. I even looked at the website for my city (rochesterhills.org) on construction for finished basements and it's requirements are very minimal from what I read (no vapor talk at all). I'm not trying to open a new can of worms here, but I have very few personal leads to research (human and media). I also tried to do a search online for methods in michigan and it's basically a 'no go'.

But if it helps with your opinions... the soil conditions here are fairly dirt/sand type of conditions... there is clay at the base of the foundation... but anything above is sand/dirt Is that bad or good? The walls inside the basement and the basement itself if very dry and has that white spray coat you see that gives it a nice finish to the walls (rough surface), but I know it's not a sealer, but probably just for cosmetic. I know this sounds silly, but I even built my first house in '02 and have helped my buddies, one of which is a builder of 20 years, finish their basements. They both applied the same method and they both live in different parts of the state, but the method was based on my builder buddy's experience... and when I ask why this method opposed to others, his reply is because that's how he learned and has continued to do it and hasn't had any complaints. I just would like the right way to do it, I guess.