Insulation, Radiant and Vapor Barriers - Moisture/Ice between insulation and outer wall of unfinished basement

I live in Minnesota and have experienced an issue in regards to moisture between the insulation and exterior walls.

My house is 3.5 yrs old and the basement was completely insulated with open faced insulation when the home was built and then covered with a vapor barrier. I have since removed much of the vapor barrier so that I could pull wire in the basement for electrical, cable/phone, etc. Now that the vapor barrier is gone and it is winter, a lot of moisture has built up behind the insulation, which wasnt there until the barrier was removed. This only occurs on the outer walls above the ground and not on any of the walls below grade where there is block.

My basement is a walkout so much of the walls on the sides and the whole back of the house are above grade. (It is/was residential code where I live when the house was built for all new construction to have all the block vapor protected with a sealent or both sealent/6 mil, then a minimum 2x4 framed wall in front of the block, then insulated and then 6 mil vapor barrier over the wall after that! Above grade has 6 mil vapor barrier only on the inside of house over insulation.)

If I try to remove the insulation it tears apart a bit because it is now frozen to the wall. My concern is that I want to make sure that the moisture will not become a mold breeding ground when I close things up again. So...

Is it safe to assume that since the house does not have any barrier on the outer wall that if I put up the vapor barrier anyway that come spring/summer the moisture will eventually evaporate and disperse out and I will be ok just putting a vapor barrier back up as it is right now?

Or should I wait for the next warm spell and pull all the insulation away from the walls and let them dry first? Then work quickly when I replace the insulation back and install the vapor barrier?

To remove the insulation is quite an undertaking and huge energy cost with the added heat, so I would like to know if this is really necessary or if the walls should dry back out once it gets to be warmer outside again.

Thanks.
Chris

The moisture is from your indoor humidity. It is getting through the insulation to the wall.

The wall is cold because a) one side is outside, and b) one side has heat to it blocked by insulation.

As for drying, once things turn to summer, the main moisture drive will be inwards, so your vapor barrier will prevent it from drying if you wait till then.

What you want to do is take a piece of breathable foam board, and put it on the outside of the wall, no, TAPE IT against the concrete wall above grade. Then remove the interior insulation, to allow heat to warm the concrete. the heat will allow some of the moisture to dry inward, but will also drive some of the moisture outward. Fortunately, you've used a BREATHABLE foam board, so it won't matter.

Thanks for the information. But maybe I need to clarify a bit.

I still need to address the outer wall that is not concrete. It is chip-board. I assume the same problem of the moisture from inside is collecting behind the insulation against the cold chip board. Essentially condensing against the cold chip board and freezing there.

Problem is that this is wood and is now wet (or has a layer of ice crystals which will become wet in warmer weather). Once I seal this up with the vapor barrier on the warm side (inside of house) right before I sheetrock, will the chip board eventually dry up on its own as it warms up in spring above freezing? Will the moisture eventually pass through the chip board to the outside and dry out? Or will it not wick away enough and likely cause mold? (Will this trap the moisture or will the chip board breath enough to dry out?)

If it will probably not dry out, I think I need to remove all the insulation against the chip board. Then plug in a bunch of fans to move the air around the basement and help the moisture come out of the chip board. (Also putting the air-to-air heat recovery unit on maximum to dry out the air as much possible may help.) Once dry, put insulation back up and then the vapor barrier.

Any suggestions or feedback on this? :confused:

Thanks!

UPDATE: It was above freezing all last night and almost 40F today so I have pulled back some of the insulation and in a few spots I see mold already has begun to grow since a couple months back!

It seems to be limited in locations, but I am now pulling out all the insulation on the chip board walls. I believe I need to get the walls dried out completely.

What then will be my next steps??? Are there any product(s) that I can paint on or spray on that will kill the mold and help prevent the mold from spreading?

Thanks!

Dominant moisture drive is from hot (humid) area to cold (dry) area. Meaning that even with heat, your wall is going to be trying to dry to the outside. When summer comes, the heat will actually push the moisture inward.

Same solution for the chip board: tape that breathable foam board to the outside, keep the insulation out of the way on the inside, and don't sheetrock until it's completely dry (spring?) ;)

First off, thanks a bunch Doug, you are helping me out tremendously.

Ok, so this seems to make sense then. If I understand correctly, you are saying that in the summer, moisture will actually drive inward from outside toward my cold air conditioned home and potentially condense inside the walls on the outside facing side of the vapor barrier - which keeps the moisture from getting to the sheetrock and in the house. So ultimately, there will be moisture of some level inside the walls that could potentially be causing mold in the long run anyway.. at least in the summer.

(if that is the case, this makes me understand why the code has since changed since my house was built and now requires the outside of the house in Minnesota to be wrapped before siding is put up to block moisture from entering in the summer... - Which now helps me understand better the whole debate people have should house be able to breathe or should they be as tight as possible or somewhere in-between?)

As for the mold. I am drying out the few spots where it was found. I plan to then clean it with a bleach/water solution. I dont think the problem was too significant to compromise the integregity of the plywood or outerwall studs and as long as the moisture levels will not get too high in the future, it shouldnt become an issue.

Ok, now my question is this. Why is it that you are recommended that I use foam board and not just stick with the fiberglass batt type insulation that was used before. (I didnt see any moisture issues until I penetrated the vapor barrier. If I pull back areas that were not compromised, they are dry.)

Thanks in advance!
Chris

The foam board is only temporary, and only has to go up in the areas that you are trying to dry. It goes on the outside to keep the wood / concrete warm. Indoor moisture won't condense on warm wood / concrete. Also it prevents you from losing too much heat to the outdoors while the fiberglass is out of the cavity.

When everything is all dried up, and the mold is gone, put the fiberglass back in, apply the poly, drwyall, and then take the board of the outside.

Ahhhhh... Thanks for the clarification! - "The foam board is only temporary"..."It goes on the outside"...

I just checked the weather report and we are supposed to be above freezing daytime highs (some days in the 40F+ range) for the next 10 days! I might just gamble they are going to be right this time!

I think in a week it should be plenty dry enough to get the insulation back in and quickly put that vapor barrier back up. (Now may be a good time to finish that last bit of electrical and get that inspection out of the way.)

With the somewhat warm spell, I think I may just pay the increased energy bill while I dry things out rather than put up the foam board (the extra work and expense could end up being the same cost..?) And only the basement back wall and less than half the wall on the sides will be without insulation - the rest is underground.

Also the clock is ticking and I really cant wait until Spring since we are expecting another child so we are going to need one of the extra bedroom downstairs sooner than later. (translation - my wife will kill me if this isn't done sooner than later!) :D

Thanks again.