Searching for the Cause of High Humidity in a Studio Aparment

[Brian Childres]

I'm stuck. I have 2 units (upstairs), 425 sq. ft. each, that recently have a relative humidity of around 72%. There are no leaks, no moisture anywhere, and we added several soffit vents. Also, the 18,000 BTU mini-splits are working fine for each unit, and it is 1985 construction, location is Tyler, TX. We discovered the humidity problem from one of the tenants seeing a small amount of green mold (this is a fairly new tenant). I have owned the 8-plex for a little over a year. Any thoughts besides installing a built-in dehumidifier? Thanks!

[Benjamin Aaker]

Hi Brian, You should check the bathrooms. Lots of water possibilities there. This could all be caused by a single tenant running the hot water in the shower for 15 minutes before getting in because they want a sauna in the bathroom. Tie the bathroom fans to the light switch right away if you haven't already done this.

[Scott Mac]

HI Brian,

-- Maybe a fresh air leak somewhere.

-- Maybe renter takes long hot showers in the tiny unit.

-- Maybe renter cooks spaghetti for a long time long in the tiny unit.

-- Maybe mini-splits are too big and not running enough.

-- Maybe mini-splits mounted too low to grab higher humid air (hot air rises).

-- Maybe it's an air circulation problem, ask the renter to put a small 9" fan (like a Vornado) on the floor in the doorway (pointed up at a 45% angle) in the bedroom. Try blowing the air in for a few hours and then spin the fan around and blow the air out for a while---see if that makes a difference. Cold air falls and this will mix the air.

 Good Luck!

[Richard F.]

Aloha,

What is the humidity level outside? Where, exactly, is the green mold? Have you confirmed your water meter is not moving, at all, with all faucets and fixtures turned off at once? Where are the water heaters located? Are any pipes underground or in a slab? Has there been any recent exposure of insulation on the exterior wall? Or added insulation/vapor barriers?

[Chris Seveney]

@Brian Childres

Having worked for a large developer that owned apartment buildings in the DC area which has some high humidity months, we ran into this often and many times it is the tenants causing the issue.

From taking hot showers for an hour and not running the exhaust fan to leaving windows open in the AM when not as hot but humid out letting that humidity in then blasting the AC during the day were two of the main causes.

[Chad Brown]

My neighbor had a similar problem and found out that the moisture is coming outside in form the cooling effect.  ground water was the culprit from too much watering the lawn and no run off away from the buildings. could be?

[Brian Childres]

@Benjamin Aaker

Excellent idea about the light switch. Thanks!

[Brian Childres]

@Scott Mac

I’ve been wondering if the mini-splits are too low. I’ll check into this. Thank you!

[Brian Childres]

@Richard F.

Humidity level lately has been around 85% outside. Green mold was found on some shoes in the closet.

[Brian Childres]

@Richard F.

Water heater is below the kitchen sink.

[Richard F.]

Aloha,

Under counter water heaters can create a lot of issues that are slow to reveal themselves. It is usually impossible to truly thoroughly inspect them. If there is seepage from a seam at the back, out of sight, or from a pinhole in the flex connectors on top, it can put a fair amount of water into the cabinet and wall space before it is detected. Also a defective T&P valve could be releasing water vapor if the unit is running hot.

I would not be too concerned about a few spots of mold on a pair of shoes...they could have been put away wet, and with the ambient high humidity and dark location could easily have developed a little mold.

Have you closely inspected the downstairs unit(s) for potential leaks?

[Brian Childres]

@Richard F.

I will check out the downstairs units. Many thanks Richard!