How to dehumidifying large unfinished basement?

5 Replies

I have a 3 unit building and the basement is dark, little ventilation and gets really humid. Which, I'm pretty sure is causing the first floor unit to be even more humid on warm days than it should be. The humidity levels in units 2 and 3 aren't nearly as bad as on the first floor unit (which is the one I'm currently house hacking). 

What's my best option for dehumidifying the basement long term? Thanks!

I'm thinking you need a split A/C system.  Not sure.  I have a house in the desert that gets hot, so I think it simply need A/C since currently we are using portable evaporative coolers.

I'd take a multi-prong approach. First, determine what the situation really is and extent of the problem. Get some real numbers on the the humidity levels of the basement and the living spaces above. If there's a moisture problem in the basement, act to resolve the moisture problem. Moisture problems can often be solved by drainage improvement, proper foundation sealing, and ventilation. An HVAC system that provides sufficient air movement is your best bet, especially with a dehumidifier built in.

Conditioning the air will remove the humidity, aka air conditioning.   Getting air flow is key to remove any condensation.   Get some portable dehumidifiers and run them.  You can hook a hose up to the tank and run it over to a drain to avoid have to empty the bucket daily.   You will want to get humidity levels to be 40% and lower in the summer.  Winter time we add humidity to the air to reach 30% - 35%.   You can pick up a small thermometer at a big box store that shows humidity for like $10.    

@Byron W. I’m an HVAC tech by profession. You want to have dedicated dehumidifier that automatically drains into the plumbing drain. It’s going to run constantly if it’s very humid. You also want to make sure your not getting water coming up from the ground(if so you may need a sump pump installed). I really isn’t so difficult to install if your a diy. Make sure gutters carry water away from the foundation. Wouldn’t hurt seal the walls and floor. Foundation paint sealer.. again diy. Don’t put in central air or split system. Try the simple stuff first.

'MOST' houses have low spots close to the foundation where over time the backfill has settled lower than normal ground level.  Filling that area so you have  a minimum of4 to 6" of slope in the first 2 feet.  Then 2-3 inches of slope for the next 2 feet.  IF their are ANY puddles within 10-20 feet of the house it is going to drain somehow back to the path of least resistance (aka your basement ).  Of course regrading your whole yard is first component of getting a dry basement.  You will  be surprised how much less your measure of humidity is in a basement by 'fixing' this problem 95% of all houses have.  Most people try to fight water intrusion from  the inside out, when the real way is to fight it outside in. (making LESS moisture to fight)

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