Musty basement

I live in east central Alabama. I have a 1500 sq. ft. basement. Half is a double garage and the other half is a semi finished area with freezer, pantry and open storage. The garage area is separated by insulated plywood walls.This summer has been terribly wet and my entire basement smells musty. There is no visible mildew, mold or water intrusion. My HVAC air handler is located in the semi finished area with one duct outlet for the semi finished area. I have a ceiling fan and a box fan that run all the time in the semi finished part. Do I need some sort of forced ventilation in both areas to pull out the moist air? Other suggestions? Thanks.

Is your basement sealed off completely from the outside air? If not, that would be your source of moisture and musty smell. The solution would be to seal off the basement, run your AC and also run a dehumidifier. It will dry up in a hurry and the musty smell will leave but you may need to clean things up to remove any mold that you can not see. In our basement, it starts to smell musty right away if we do not have the dehumidifier running when it gets muggy out. The cool basement walls and floor will condense out moisture from the air in the same way the cold coils on the dehumidifier collect water. But on days like today in N. WI, the dew point was only about 50 so we opened up all the basement windows to air things out. The dew point is key - 55 to 60 means slightly humid, 60-70 means humid, and 70+ is very humid. If the temperature of your floors or walls are below that dew point, the moisture will collect.

You don't realize how much water is in the air till you empty the gallon of water out of your dehumidifier every few days - and this is just inside air with moisture that makes its way in under doors or through floors (our basement is closed off). If you were to run a dehumidifier with outside air coming in you might collect a gallon or more of water a day!

No, I would say it is not closed off from outside air. There are no windows, only two garage doors. If we leave the garage doors closed, the musty smell comes on pretty quick. If we leave one or both doors open the musty smell is not so strong at all, but I sure the open doors, even though they seem to help with the smell, contribute to the problem in the end.

A dehumidifier is a good first step, but if you don't want to spend the bucks you have a couple of options to see if it would work. Something like a Damp Rid collection system.

I've also tried coffee filters in the back of a fan, it seems to cut back some of the moisture.

Aside from that I would recommend a good ionizer. I've not found anything that can kill smells like that thing.

Whatever you do, keep in mind that if you do not seal off the outside air, you will be allowing literally gallons of water back in if windows are left open. A dehumidifier will dry the air nicely, but it also gives off heat. An AC unit, even a window unit, will dry the air and cool it too. We have both a dehumidifier and medium sized window AC unit (rated for about 600 sq ft I think) to keep our basement both cool and dry when it gets hot and humid around here. And when it gets dry I open all windows and will even put a fan in the window to bring fresh air in. But I would imagine in AL it does not get dry too often in the summer.

Yes, it runs about 80% humidity during the summer here. Thanks for the advice. I'll look into a dehumidifier as well as what I can do to seal off air from the garage area.

Is there a weather-strip door between the garage/living space, a fire door?

Is there 5/8" drywall (Type X) between the two rooms?

Gary

No, it's 1/4" plywood on the outside, R11 insulation and 1/2" plywood paneling on the inside. Hollow core doors, no weather stripping.

My guess is that the mold is in the plywood. No dry wall down there? You probably need to gut the whole thing, should avoid any natural material in the basement in the future.
No ionzer or dehumidifier will get mold out of wood or dry wall. Only minimizes it.