Mold in rental property

[Jay Cho]

Hello all

when I recently visited my rental property I fount a lot of mold and very high humidity level. I could feel it and found sweating walls and windows.

My rental property has water circulated heating system heated electronically.

My tanents didn't open the windows for circulation often.

I added more insulation to the attic and changed the tyvek, sidings and windows recently.

there is no leaks from the roof or water line. No leaks thru windows.

do you think the mold is caused by the heating system? Do you think if I change the heating system to electric baseboard system, will this problem be solved? 

Or should I install an air exchanger or heat recovery unit? 

Thank you for your help