desperate for bsmt condensation advice!!

abfab

I have a one bedroom basement apartment with humidity problems and can't figure out what is causing it. It was vacant last summer (I've only had house under 2 years) and don't recall ever seeing moisture down there. Having said that I did build a patio and flower beds last spring.

The entire area has tiled flooring, but only the bedroom seems to get condensation, especially after a heavy rainfall. The bedroom and living room each have two exterior walls, the bathroom has one.

The house has central ac and I have tried running its fan 24/7 to dehumidify the air, but its not solving the problem. I also checked the sump pump which is working fine as well as the easetroughs, so I don't think its a leak. You can feel the humidity when you're in the room.

The adjoining washroom does not have an exhaust fan, so tenants open the windows for a few minutes to let the humidity out... they say showers are less than 10 minutes, door is closed during shower and window is immediately closed. The bath window has a plastic window well cover over it (its too hard to take off in summer because window wells not constructed properly) but there is some ventilation at the bottom of it.

I thought about installing a bathroom fan, but not sure it would solve the problem since the condensation is in the bedroom not the bathroom. I don't want to go through all that work and find out its still happening.

Is it possible that shower humidity would be problematic in an adjoining bedroom, but not the bathroom itself?

Why would the condensation problem be worse after a rainfall?

I'm really confused and unsure what to do next. Any advise would be greatly appreciated!

oddjob

Have you checked your gutters and downspouts. maybe an overflowing gutter adding to moisture permeating your basement.

MAS2006

Condensation occurs when moist air comes in contact with a cool surface. Humidity is higher after rainfall. AC will dehumidify air not just running fan. Try stand alone dehumidifer unit. If walls are concrete should have proper footing drainage and or moisture proofing.

alissakk

I had a damp basement in a rental home - there was no signs of leaking in that basement - I ran a dehumidifier with some success - however, my problems vanished when I installed a exhaust fan - Unfortunately, we did have to run the fan at all times, but it was worth it to rid us from condensation on the walls

coolmen

Adding return air at the bedroom area will help.

#CARRIERMAN

Hi abfab

Know I may be a little too late, but first is to understand what causes this problem. Like the other have sugested this is due to moisture in the air. Now we will break it down. Assuming the house has proper drainage, that walls do not have artezian springs running through them. What causes condensation is a temperature differential. Let me explain, the basement I am assuming is totally underground and not partially exposed. When you take the temperature underground stays anywhere between 50 to 65 degrees year round there is one temperature source. The second temperature source is the air that is inside the room. The air temperature and moisture content inside the room will constantly change due to the nature of convection. Now as a HVAC man this means sensible and latent heat, but we'll not get into that. What will help your situation is to take into consideration what options are affordable as well as viable. Not many people in my field have the insight to install a return air in the basement to alleviate this problem. If this is the case, by adding one to the basement that will accomodate a total air exchange every 15 minutes will solve your problem without alot of cost. Your HVAC company will be able to help you with this. You had the right idea by running blower continuously, but the reason it probably did not work is there is no return in the basement. Option two would be to put in a power foundation venting system, this is slightly more expensive than the first suggestion. I would not reccomend this unless you are using basement for storage only. The third would be to get a dehumidifier. This is not necessarily the best option either due to the fact of maintenace of it.

Good luck, If its not too late, let me know if I can help you further.
Rusty