I recently had a gas fireplace/stove installed in my basement. The vent pipe has condensation on in when it is not in use. It has been cold this winter and the condensation has been freezing. This creates a giant mess anytime I run the fireplace with water dripping everywhere. The guys who installed are being helpful and trying to fix, but they don't seem to know the problem. The pilot light has been on the entire time. The black pipe on the inside of the house is extremely cold, all the way down to the unit. Is that normal? Suggestions?