My basement is a mess. I need advice.

I have about 500 square ft for my basement. I had the humidity tested the other day and it was extremely high, so I decided it was time to do something about that. A basement systems salesperson wanted to sell me an $1800 industrial grade dehumidifier to dry up the air, but I couldn't rationalize spending that much money on a piece of equipment that big for only 500 sq ft.

I picked up a 70 pint energy star dehumidifier instead that is really working it's tail off. It's only been 2 days, so I can't really tell a whole lot of difference, but I have emptied the tank 4 times now (each time it was almost half full). Now I've got a hose hooked up that runs to the drain.

I don't have very good insulation down in my basement and my walls are nasty. They are discolored (mold?) and chipping. When I start to remove the chipping outer layer, it sometimes crumbles a little bit. A couple of people have told me that I could clean that up with a steel brush or a pressure washer then paint it with a sealant. Is this a good idea or could it possibly harm the foundation?

My basement doesn't get that wet really. This summer we experienced some very heavy rains and a there were a LOT of wet basements in my area. I got lucky I guess. A few puddles and damp spots, but I didn't get flooded. I don't have a sump pump or anything, but I would consider adding one down the road. One thing at a time.

The thing that I'm worried about right now (aside from the walls) is the lack of insulation down there. There's no insulation underneath the flooring above, there's no insulation on the band joists or on the walls. Is it a good idea to clean up and seal the walls first then put in some insulation? Also, what kind of insulation is best for a basement? Spray foam? Bat insulation?

My house was built in 1919 btw. Any feedback would be appreciated. Thank you.

 

It would help to know what part of the country you're in. Does it get cold there in the winter? How many heating days there? Basements are usually the last place you want to spend money insulating, because if your basement is like most, with only about 2 ft above grade, they pretty much will stay a constant 50F in the wintertime, so insulating them you aren't really gaining that much in energy savings, as compared with insulating walls or attics.

 

Live in Iowa with a mixed climate. Both extreme hot and cold.

 

My water table pretty much touches the bottom of my basement floor. I get a lot of moisture through my slab into my basement. Early last June it was 80% RH in my basement. I picked up a dehumidifier and took several days until it was down to 50%. After that it won't need to run all day. You should pick up a digital hygrometer. They are cheap to purchase.

You are not going to be able to seal the moisture out. The best you can do is to ensure that you have your rainwater draining properly away from your house.

You basements walls should be insulated only on the parts above grade and one foot below. That allows heat to escape from your basement and into the soil to help reduce frost from forming against your foundation. The danger of that happening is that the soil can expand enough and damage your foundation. Use foam insulation against the walls because it will still allow the moisture to pass through instead of being trapped between the insulation and the wall.