Glad to see you found a leaky area to seal up. However, your construction doesn't sound all that normal. Would it be possible for you to get some pictures of you joists with and without the foam?

I do have some pictures but don't have a place to host them. I thought it was strange but I asked around and it is apparently common in this area and that era of home ('74 construction). The joists are actually set in the concrete nearly up to the top. Apparently it may have been to do with tornado codes (though they are rare here). Those things sure as heck aren't twisting!

*Edit* Pictures attached. You are looking down the joist bay to the exterior. You can see the concrete wall with a small gap above. You can see the foam peeking out at the top.

When you post a message, you can attach images to your post so you don't have to hose them elsewhere.

Here is a quick write up on how to do it:

http://ecorenovator.org/forum/forum-...-pictures.html