Dehumidifier in basement

17 Replies

Hi guys

I have an older two family which has such high levels of humidity in the basement that I am constantly replacing joists and other wood due to rot. I think the best option is to run a dehumidifier.

In this basement I built a small 10x10 room in the corner with a locked door for my “boiler room” with my two wall-hung Naviens and other things I keep for storage that I don’t want my tenants touching. I would like to put the dehumidifier in this room so none of the tenants mess with it (and also because there is an outlet in that room)

My question is: will the dehumidifier “suck” the rest of the humid air from the rest of the basement into this room? The room is not completely air tight, there are gaps near the ceiling joists that would allow air flow.

So before i go out and spend $400 on a dehumidifier with a pump, will this work? Or does the dehumidifier really need to be in the open area of the basement. I am planning on leaving it running full time.

Also anyone know what the electric cost is per month to run one of these things full time?

I run 2 dehumidifiers 24/7 in the basement of our 6-plex that drain into the sump pump wells & both units are 5-7 years old. Our biggest problem is moisture seepage from the original hand dug basement walls but given the effect on your joists your moisture problems seem excessive.

I have no idea of electrical $$ as its tied in with the common area billing but I'm sure its minimal. During the winter our old boiler dries the basement out perfectly & our 1950's joists are solid & have absolutely no moisture issues like you mentioned. Our old NG boiler is still viable & reasonable to run vs swapping it out for an on-demand system that I will eventually install, but I would them have a moisture problem all winter.

@Frank Maratta I also have a property that I run a dehumidifer in the basement at all times but i leave it out in the open and my tenants dont even acknowledge it. I dont remember spending $400 on it though and i didnt even notice a difference in electrical costs.

@Pat L.

Do you know if I can run a dehumidifier in the winter? As you mentioned, my naviens do not help much heating the basement.I heard the coils on a dehumidifier will freeze if run in the winter

I’ve gotten and used a couple of these on a few properties. I like them as they are energy efficient, run only when needed, and are pretty inexpensive.

Whynter D Energy Star 30 Pint Portable Dehumidifiers - Elite Series, Multi https://www.amazon.com/dp/B00V69GJOU/

I first purchased a 70liter one, but it was very noticeable on the electric bill... not good. Sold it and got one of these instead.

I couple it with a standard AC condensate pump if I can’t put it in a shelf to gravity drain.

And if you put it in your ‘boiler room’, I’d definitely add a couple vents in the room to let air flow.

While you’re at it, make sure any gutters are away from the house. It’s amazing how much you can often control moisture with simple fixes - though obviously not always!

Originally posted by @Frank Maratta :

@Pat L.

Do you know if I can run a dehumidifier in the winter? As you mentioned, my naviens do not help much heating the basement.I heard the coils on a dehumidifier will freeze if run in the winter

Don't know about the dehumidifiers freezing but if its that cold humidity is minimal so why run it. Ours are old GE units so whenever the one we have at home gets older I just move it to a rental. 

I recently bought a 70 pint one and it made a difference almost immediately ( well , within 2-3 days). 

Humidity Level went from 

85 %to 45 %. 

Should be in open space to work effectively. 

No need to run it in winter . 

Not sure why you think the tenants will mess with it , especially when it improves their environmental quality. 

If tenants are willing to "jack" the dehumidifier you may have bigger problems....
However, you could always make your boiler room open to the rest of the basement with a wire mesh or chain link wall instead of a solid wall.  Even a partial wire mesh wall or chain link wall should do the job

@Frank Maratta

You are trying to close the door after the horse ran out of the barn.

You need to figure out the root cause of where the moisture is coming from. If you don’t already have a French drain type system to manage moisture water coming through the walls then that should be step one. If you get this work done make sure to run the plastic waffle board up the wall as high as the ground level outside. Is the space in the lower level conditioned with some sort of ductwork that at least move the air around so that it doesn’t become stale and potential mold source.

As others have mentioned look at your gutters and where they drain out. Best to bury some hard pipe to carry the rain water minimum 20-30 ft away from the house.

A decent sized dehumidifier will cost $20-30 per month if its running on high 24/7 and that should be on your dime, not tenants. You could cut some vents high and low in the walls of your secure room to promote air flow and dehumidify the space outside the room.

@Pat L. I like the idea of draining into the sump pump... must be the standard. Does this make it possible to finish a basement with this much humidity? Would drywall such as green board hold up ok?

Originally posted by @Jonathan Greer:

@Pat L. I like the idea of draining into the sump pump... must be the standard. Does this make it possible to finish a basement with this much humidity? Would drywall such as green board hold up ok?

 We finished a high humidity basement (pipes were sweating) earlier this year with just 3" foam insulation & 1/2inch fireproof drywall (as its livable & has an egress window). Before the rehab of it the humidifier ran constantly but now it's rarely running. So I put the collection bucket back in to test the volume of moisture & found it ran 3 weeks with barley a cup full of moisture collected. But all the original cement walls & flooring were tight without any wicking so the source was in-house humidity.

@Pat L. Wow, sounds good. Also, those egress windows are a whole ‘nother thing.. sounds like I’m finishing things up and making them tight as possible actually reduced your humidity too + the dehumidifier a win win.

Originally posted by @Jonathan Greer:

@Pat L. I like the idea of draining into the sump pump... must be the standard. Does this make it possible to finish a basement with this much humidity? Would drywall such as green board hold up ok?

 You should figure out where the water is coming from before finishing a basement. In order for there to be enough moisture to rot wood, that is a pretty serious moisture situation. If it is coming in the basement walls, you don't just want to trap it behind the wall, because a humidity problem could become a mold problem. 

There are options like painting walls with Drylock to keep moisture out. I have used humidifiers at a couple properties and I just run a tube right to the drain. A cheap one will run for 3-4 years before needing to be replaced. Tenant never messed with it.

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