High humidity in rental home

[Tyler Todhunter]

Hi everyone, 

I have a problem and I'm hoping someone can help me identify a solution.  I have a single family rental home and the renters have been complaining about the walls being wet and causing a mildew/mold problem.  I had a handyman check the property and he said that the water wasn't coming from the roof, but that there was some preventative work that could be done.  He also said the exterior walls had no insulation.  I paid to have the roof fixed up, additional insulation put in the attic, and insulation blown in the exterior walls.  

Two weeks later, I get notification that the problem persists, so I went to investigate myself.  The walls in the bedrooms were definitely wet, and showed signs of mildew.  The concentration of the moisture was low- much less towards ceiling and wetter towards the floor.  The floor, in some places, was actually wet.  The house was extremely humid (and about 70 degrees), like running the dryer with the exhaust venting inside.  I checked the dryer vent, and it was blowing outside- and the walls near the dryer were much dryer than elsewhere.  I looked in the crawlspace under the house, and there was no standing water.  The exhaust fan in the bathroom was functioning.  

The level of humidity in the house was very abnormal, but I can't seem to find any reason why.  Does anyone have any ideas where this moisture may be coming from, or ideas of what else I can look into?  I'm really stumped and any input would be greatly appreciated. Thank you!