Question on a rental that we just found out has mold. House is 1400 sqft on main floor with same size unfinished basement. Five people plus two dogs live in the house. Main floor has one bathroom with tub and no vent other than a window to the outside. Basement has a old shower in it that is used every day but is not vented to the outside. The windows in the basement are not sealed good so there is some air movement. Roughly two years ago we had the floor of the first level insulated and a vapor barrier installed. We also had insulation added to the attic. Recently we found out after the insulation was added the tenant started having mold issues in two spots in two entirely different rooms. One spot behind their couch and the other in the kitchen under the sink in the cabinet area. Before we found out about the mold we had discovered the vents to the roof had all been blocked of from improper installation when the house was built. It has since been fixed.
We are now trying to decide how to proceed. We took some readings in the house and humidity was around 57 on the main floor. My house at that time was 50% and I live a hundred feet away.
First option is to place a dehumdifier in the basement to remove moisture from the shower to see if that drops the humidity on the main floor.
Second remove the vapor barrier that was installed on the bottom of the first floor since I guess the mold did not start until after the insulation was installed.
We wanted to do more upgrades to the house (insulation and possibly heating system) but are now holding off till we can figure out why there is mold. Any thoughts or advice would be appreciated. Something I should add is the house always feels stuffy. The house has electric baseboard heat and the renters usually don't like to open the windows on nice days to get air circulating.