We recently bought this house, and I'm pretty sure the previous owner just painted over the cynderblock walls since there were plenty of bumps on the walls, which - when rubbed, paint came off and it looked like a white chalky substance. Also now, I see a nastier looking substance appearing mostly at the lower foot or so of the walls - kind of a greenish brown color. I havent tried to scrape this substance yet. We have a sump pump installed and working with piping that runs to the hole from what looks to be around the basement. There is also a 3" cutout around the floor which I dont see any moisture in. There was exess moisture coming in - I thought since the house had no outside drainage. So, I installed seemless gutters on it. Question: I plan on finishing the cellar some day and I want a healthy environment. So, should I get this substance tested or something? If I've already done what I can - gutters, sump pump. Could this be being caused by outside water coming through the walls, or just excess moisture from the opening of the washer/dryer and it is condensing on the lowest part of the walls since it is colder? I had a dehumidifier running but Im waiting for recall on it.

I am finishing my basement with 2X4 walls, but hung the poly against the cinder block walls versus the interior side of the 2X4 walls (based on old contractors advice). The walls are 1/2" out from the cinder block. 1.) Is there risk in having the poly against the cinder block versus the 2X4s? (Had the basement tested for moisture and had no evidence or presence of water) 2.) What insulation would you recommend for the basement(I live in Minnesota)? Thanks, John