We have noticed in the past month a very high humidity level in our home. I took a reading yesterday and it was 79% rh in the house. We have done nothing different in the past month that would cause this that I can think of. We tightened up the house with new windows and siding two years ago, other than that nothing new. We have an old stone foundation and the basement has always been damp. The weather has been mild reciently so we have had the windows closed and kept the furnace off. I checked the dryer vent, it is clear and hooked up. We do not have a bathroom exhaust vent. Any ideas would be greatly appreciated. Thanks in advance for any help.