Insulate over basement efflorescence?

[bob smith]

Hi all,

I'm getting really to insulate and drywall a portion of my basement in an older (1950's) house. The basement foundation is cinder block, that looks like it has been covered with some kind of a tar-like sealer, and then plastered.

I have been monitoring the walls for the last 8 months and there are no water issues. I do however have some moderate efflorescence on one of the four walls. This wall is adjacent to the driveway beside my house. Some of the driveway stones do need to be reseated to properly grade away from the house, and this is on my list of stuff to do this summer. That should reduce the efflorescence but probably not eliminate it.

Because I dont have access to the raw foundation wall, a sealer like Drylok is not really an option. Nevertheless, I plan to coat the surface with an efflorescence-fighting coating anyways. Of course, these kinds of treatments only work for a limited time (5 years).

Anyways, bottom line - can I proceed with insulating over this? I was thinking of using a closed cell spray foam insulation. Would that be recommended for this situation?

Thanks!

[m Ransley]

Efloresence is water pushing through. The only way to monitor it is with a moisture meter. Seal in moisture leaking in and mold will grow. There is no efloresence stopping product that I know of. Stop the water from the outside.

[bob smith]

Something like this:

to stop efflorescence.

I believe there are serious implications to consider when disturbing the earth (to waterproof the exterior) down to the bottom of the foundation when its under a driveway. I dont want my driveway sinking 5 years from now.

If I use a vapor retarder (like a spray foam) rather than a vapor barrier, it seems to me the small amount of moisture coming through the wall should be able to dry to the interior. But I guess thats the heart of my question.

[JimL]

When you insulate the efflorescence wall, you are going to grow some super mold that may or may not be deadly. Currently, you are drying off the surface by exposing it and preventing the growth of mold.

My solution would be to place a mesh over the wall prior to applying the insulation and then permit the top and bottom of the mesh to be exposed to the room so that air would flow thru the mesh. This procedure is used in many foam foundation product installations to prevent mold/moisture.

[Roy Starrin]

Provided you get the existing efflorescence off the surface first by the usual means===muriatic acid wash. What is sorely needed is a means of killing it without the fumes rusting out everything in the basement---inluding your lungs.

I thin just the issue of disturbing the earth is a problem. Had a huge tree, next to the basement, roll on the house during Isabel. Impossible to get the stump out and/or get to all walls of this partial basement(Trust me), So, my water problems have started anew.

[bob smith]

Not a bad idea, thanks. However, these foams are typically referred to as 'vapour retarders' not vapor barriers. As such, they do allow moisture to dry to the inside at a controlled rate. Is that not adequate?

[JimL]

Mold can be deadly so don't try to win a semantics discussion and lose your family's health.

[Beeper]

[Harry Everhart]

How do you get air moving in that 3.5 inch cavity? How do you know it is moving "nicely"?

When the humidity stays above 75% for long periods of time - that is when mold will grow. You can kill it with a solution of 75% water and

25% chlorine bleach. Then ventilate it or run a dehumidifier. We have a summer home in PA. In the winter when the heat is running - the humidity in the basement stays low. In the summer - we run a dehumidifier to keep it fresh or open several window and run an exhaust fan.

In our Florida home - we must run the AC all summer when we are away. If we do not the humidity goes up and mold will grow in the house. In the winter - it is not a problem.

[JimL]

If you provide a way for room air to enter the cavity at the bottom and to exit the cavity at the top then simple physics will handle the movement for you. If the basement is not otherwise conditioned, then a 24 hr a day (ceiling) fan would give extra insurance at little additional cost, but I might go for a cheap wall refrigerated unit if I lived in So. Florida.

Although I have central air(3 1/2 ton), I added a 5600 btu refrigerated wall unit (11 eer) that solves that problem and does so very economically. It cut my summer electric bill in half and we are so much more comfortable, too.

[bob smith]

My point was not to argue semantics. a 6mil vapor barrier sheet has a perm of 0.1. Closed-cell foam has a perm of around 1.4, and some open-cell foam can be over 10. So they do allow the moisture to dry to the inside. Also, this page:

Specifically mentions that spray foam is a good solution for spaces with some moisture problems.

[Goedjn]

If you have a 3" cavity between the foundation and the basement walls, haven't you just built yourself a mold-farm? (And a lovely space for mice, to boot?) and if you exchance air between that space and your living area, you've accomplished nothing. And if air-changes are enough to keep the surfaces dry and mold-free, you're better off not covering them at all, but leaving them open to the living area. The only way this makes sense is if you're doing the air-exchanges through a fairly good filtration system.

[bob smith]

I would tend to agree. The proper way to do this would be to vent this space to the outside above the grade.

[breadfan]

moisture problems. That's because it won't encourage mold growth like batt insulation can.

Yes I know this is 13 years old, F off.

[ItsJoanNotJoann]

Another dumbass from HomeMoanersHub strikes again. What makes it so damn silly is the idiot KNOWS he's replying to a nearly 13 year old thread but somehow thought his post would be earth shattering news.