Expert: Bruce E. Johnson - 1/13/2009

Question
We bought a house in upstate NY with a finished basement last winter. When spring came the mold/mildew smell in the basement was overwhelming. We began to dig into the possible areas of concern and found insulation installed incorrectly above a dropped ceiling, wood paneling glued to raw cinder block walls, and carpets laid directly on the slab floor. All 3 areas were just collecting moisture and were so moldy and nasty it makes me sick just thinking about it. We completely gutted the entire area. We are now left with just painted cinder block walls. The front of the house is completely underground, with the sides only half under ground, and the back of the house is not under ground at all. The house is now freezing this winter compared to last, so we want to insulate the basement walls. We heard that cinder block "bleeds" moisture and we want to avoid the same smell/health issues we just corrected last year. The area is not used for anything. Is there a proper way to insulate cinder block walls?

Answer
Hi Mike, the problem you have with the moisture is probably from a clogged, poorly installed or totally missing footing drain and proper waterproofing.  

A typical basement below grade has the exterior walls thoroughly coated with a heavy mastic, or tar to stop the moisture from penetrating the masonry or concrete.  Then at the footing elevation a layer of rock with a perforated drain pipe is installed to collect ground water and pipe it away from the foundation walls.  This pipe either is discharged downhill somewhere or drained into a sump and pumped out as needed.  If these above steps are not taken or if the drain is clogged then no matter what you do you will always have water penetration. Water will build up around your foundation wall and if it sits there long enough it will find a way into your building especially if there is little or inadequate waterproofing on the exterior.

As far as insulation goes.  Stiff styrofoam with a foil face is good if you have no other options.  Some areas have foam core fill insulation available.  This is ideal.  They drill holes into the masonry and inject foam.  We use this method almost exclusively in Florida for thermal protection.  Vermiculite is also an option.  You punch a hole in the top of every fill cell and pour in vermiculite until the cell is full, then patch the hole.
I hope this information helps, feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com