mold on walls in two spots with high humidity?

[grizzzlle]

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.

Thanks

[drk]

First add auto bath fans to the bathrooms. These will cut on when the rh gets to set level. Second a dehumidifier will be a good idea. Reduce the rh clean the mold and I bet the issue will be fixed.

[skippedover]

When you say the bathrooms/showers are not vented, I'll assume you're speaking of exhaust vents and not fixture plumbing vents?

In order to prevent the colonization of spores with resultant mildew and mold, the humidity level must be maintained consistently below 55%. At 55% and above you can expect to have growth issues. Under kitchen sinks is textbook for high humidity due to minor water leaks and the cabinets and floor never fully drying out. Overall, from your description, the interior humidity levels are too high. Dehumidification, exhaust vents for the bathrooms and kitchen should do a good job of controlling the issues.

[mdm0001]

I have a small dehumidifier we use in the large bathroom when showering. The exaust fan does nothing to help. This really helps to prevent condensation on the register.

[skippedover]

You never answered my first question but let's just proceed.

To grow mold you need to supply 3 sets of conditions.

1. Consistent moisture
2. Adequate temperature
3. A food source.

Since temperature will not be changed and the food source is unlikely to be eliminated, moisture is your only variable that can most easily be addressed. Given that you have a liability situation (the tenants could sue you and win handsomely if they are prone to any allergies) I'd recommend some definitive action. Removing this or venting that and then waiting for results that could be weeks or months down the road is certainly not definitive action.

I'd highly recommend you have a whole house dehumidifier installed post haste. You need to accomplish two things immediately. First, show that you are taking definitive action to look out for your tenants best interests and health and second, to insure that the mold growth will be stopped. You'll still need to deal with the areas where mold has already colonized and you should continue with eliminating the issues that are blatantly problematic. But taking action that speaks loud and clear that you're doing something other than guessing and waiting will go a very long way in protecting both you legal as well as your financial interests, the financial being your investment in the home itself.

[grizzzlle]

Skippedover to your question yes I was originally trying to say they did not have power ventilation. Since the original post powered vents have been added to the kitchen and on the main floors bathroom. We are in the process of deciding what is the best way to eliminate the use of the basement shower I.e.upgrading the shower on the main level. We did not realize how much the basement shower was being used. As per the first recimendations I purchased a dehumidifier but last time I checked the renter had not plugged it in. As to an entire home dehumidifier the house is baseboard heat. There are no ducts at this time. We have gotten one bid to add ducts for forced air heat in order to help lower the tenants heating bill and also now to help circulate air within the home.

As far as liability we always do our best to fix problems as soon as we find out. We have a harder time with some renters though telling us about problems when they start or are small problems. Had one renter not tell us about a roof leak and when we finally noticed the problem we had to redo all the sheetrock in one room and replace carpet and pad. When asked about it the renter said it had been going on for little while but did not want to say anything. They did not want to cause problems.