Musty basement

[rockycmt]

I have a 100% underground basement with no entrance. Only 4 small 2' x 1' windows, one in each corner. The basement has never had any water seepage. Floor is very dry. I plan to take down the 3/4" T and G paneling and redo the entire basement with mold proof materials. But right now there is a very potent musty smell, which I would like to minimize. I have all 4 windows open all the time but this does not produce much ventilation. What can you recommend to help alleviate this problem? I thought about getting a dehumidifier. What kind or results should I expect out of this?

[jadnashua]

Mildew requires three things: the spores (almost impossible to not have one around), moisture, and food. Get rid of any one or more of those (after you kill any active spores), and you can keep it from growing. A hygrometer is fairly cheap...see what the relative humidity is in the basement. Somewhere around a low of 40% would be nice, but values greater than 60% could be problems.

[Chris75]

I would highly recommend a dehumidifier, but size it to the sq. footage... dont buy something to small.

[prashster]

Is the floor currently carpeted?

[rockycmt]

Good question. No, It has one of those poured epoxy floors. The only thing down there to absorb moisture is the 3/4in paneling.

[prashster]

Does the paneling have insulation behind it?

Replacing the paneling and (if any) insulation will immediately make a difference. The humidifiers will delay the recurrence. I'd drain the dehums directly into your sump (if any). Else you'll be doing a lot of up and down the steps draining full buckets.

[iamjcl]

I have a basement (with doors into, and some large windows) that also has a mildew smell (only summer / humid months).

I'm about to finish it - currently no insulation or wall covering - just studs and the foil side of foam insulation board.

What should I do before sealing up the walls ?

I've been considering using spray foam insulation (supposedly less mildew prone) in the stud cavities, and paneling with 3/4" cedar.

I will have a mini-split installed to handle HVAC in there, so hopefully will be able to keep humidity in check.

Carpet will be installed as well.

Thanks for any other info or tips anybody may have.

- Chris

[xroad]

I never like the idea of a finish basement. Too many baggages. Open window wil let in moist air into the basement. As soon as it hit the cold(er) basement wall and floor, it will codense. Any other object in the basement will be at thaat temperature and will have water condense onto it as well. Think rusty tools. I have dehumidifier runnng on a timer. Summer time, every 2 hours or so, it will run for half hour. As the weather hets less humid, the time between run will be longer. Everything smells dry, feels dry.

As for the baggages ... anything you put over the wall will slow down the drying of any moisture on the surface. Covered walls often means trapped moistures. Moisture wil also come from the foundation walls. That is why many attempts to paint the walls failed. The hydraulic presure will push it off.

[alternety]

imjcl - spraying over the existing foam should fix things but you need to cover all the edges where air could be exchanged from behind existing sheets. Spraying is quite expensive. You need to get enough insulation in place to avoid having moisture diffusing through the finish wall material condense behind the finish wall. Ask the insulation contractor what you need in your climate.

[xroad]

imjcl - spraying over the existing foam should fix things but you need to cover all the edges where air could be exchanged from behind existing sheets. Spraying is quite expensive. You need to get enough insulation in place to avoid having moisture diffusing through the finish wall material condense behind the finish wall. Ask the insulation contractor what you need in your climate.

Alternety, & All,

Ii always wonder about that. If I use solid foam insulation panels, or spray foam on the wall, sealing all the edges and seams, in effect, I am totally sealing off the 2mm of space that separates the concrete block wall and the foam. Would mold grow in that space? The living space would be isolated, I know. This question is almost like asking if mold grows in the hollow space of the concrete blocks. Inside the blocks, I don't care. In the gap between the wall and the foam, I may. Imagine someday, I or the next owner rips open the insulation and find a 2mm layer of mold. Is this a concern?

[D.Smith]

Couple of things I would reccomend. Measure the cubic sq ft and get a dehu large enough, install a cold air return to force air exchange, remove all the paneling, and rent a air scrubber.

[alternety]

If you have the proper R value, moisture would not condense in the wall/insulation sheet void. If you were doing it from scratch I would spray directly onto the wall. Removing the installed sheets is more trouble than it is worth. I would also be sure the potential air exchange locations are sealed. Belt and suspenders sort of approach.

If you want to do it with additional sheets of foam I would use closed cell polyurethane. Best R value and no appreciable moisture migration. The problem would be that you have to seal all of the joints. That could be tough.