I have a heat pump system that is increasing the humidity in the house when it is in heating mode. So much so that when the heat pump comes on condensation starts to form on the windows.

It only affects the rooms where the heat pump is heating and even then it is not equal. For example, I have one zone that has two rooms. When the heat pump comes on the windows in one room fog up, but in the other room which is directly adjacent they do not, so the moisture might just be coming from one supply--not sure how that could happen.

How can I further diagnose and fix this problem?