Just bought a new townhouse in September. The basement area is small
because it's not the full footprint of the house. About half of the
basement is above grade. My husband has a 120 gallon fish tank and a
40 gallon in this room. The back wall of the basement is insulated
with fiberglass insulation (there is plastic on the outside). The
insulation is about half way up the wall.

Since it starting getting pretty cold, we are noticing condensation in
the back right hand corner of the basement, but nowhere else (we've
tried to check behind the insulation and don't see anything). I've
been running a dehumidifier to keep the humidity around 40%. We see
the condensation forming about half way up the wall in the corner which
is above grade. I understand that this happens when a cold surface
(the concrete) comes in contact with humid air. I just don't
understand why we're only seeing it in a small area and why it's not
happening all over the concrete in that corner. The corner isn't
insulated...the insulation runs up to that point and then stops.

Is it possible that something's wrong with the concrete there, is this
simply the coldest part of the basement? There are large windows in
the room that have absolutely no condensation on them. I'm just trying
to determine whether this is something I can go back to the builder
about, or something we'll have to deal with going forward.

Thanks,
Jamie