Dehumidifiers - settings and hours of usage

[catccc]

We have a automatic dehumidifier set to 55% in our basement. (up from 50% that my husband initially set.) It is plugged in 24/7 and runs however much it needs to. 

Last year, I would unplug it overnight and plug it back in in the morning, figuring that was enough humidity control.  I had read it is okay to run a dehumidifier for about 12 hours a day, and have it off the other half of the day.  I assume this rule was made up for manual dehumidifiers, and I want to assume the same rule is okay for automatic dehumidifiers, but I'm not sure.  A manual one on for 12 hours straight would potentially bring the humidity down to lower than target, putting the space in a better position to deal with the next 12 hours with the dehumidifier off.  Of course I don't want to be too stingy, we want to keep the basement dry enough to stay mold free.  This year, I have left it on mostly out of laziness, and the electric bill shows it.

Any thoughts on the best way to dehumidify and reduce electricity usage?  Should I bump it down to 50% (or lower)and run it for half the day instead of running it at 55% for the full day?  Are there any non-electrified desiccants worth considering?  Do I need to be running this thing all winter long?  We are in the mid-atlantic area, philly suburbs. 

Also, due to the electric outlet placement, it's about 6 feet away from a 4 x 4 x 6.5 grow tent (DH is really into houseplants).  The grow tent humidity is at 70%.  The grow tent is def not airtight as it closes with zippers and has other little access portals and cinch closures here and there.  I suspect the grow tent is making the dehumidifier work a lot harder than it used to.  I've asked DH to try to seal the tent more - maybe it would be worth throwing a plastic tarp over a side or two?  My understanding is the grow tent needs some air circulation, so we can't seal it off too much, but maybe a little wouldn't hurt.

I've read a lot about RH and basements and find a lot of contradicting info, like anything below 60 is fine, or you want to have it at 40 to be sure.  Same with how long they should be on, some people say all day and some say half the day.  And same with having it on in the winter v. not.  If anyone has thoughts, advice, or resources that can help me decide how to handle this, I'd appreciate it!

[Sibley]

If you need a dehumidifier, then you need it. Playing games to reduce energy usage is more likely to cost more money to fix the mold problem that will eventually develop. Whether you need it in the winter or not depends on your climate. In areas where it gets cold, running the furnace will dry out the air. For me, dehumidification is a summer issue, I actually have to humidify in the winter.

If your dehumidifier is undersized for the area and/or amount of humidity, then it will run constantly. Get a larger one. Increasing overall air flow can help control humidity, but if its 90% humidity outside you're going to have high humidity regardless of airflow. Properly routing water away from the foundation can help reduce the humidity inside. Check your gutters and drainage outside.

40-60% RH is the range that people are comfortable at. In the winter, I aim for 40% and don't get there. In the summer, I aim for 50%. I'm in Indiana, where it's hot and humid in summer and cold and dry in winter. Your climate may be different, so you might be running it a different times than me.

[chemistk]

I also agree that this is one of those appliances that you should prioritize its function over its energy consumption. We keep ours at 50% and that's where it stays. I'm reasonably confident that running it for 12h cycles is going to be causing more harm in the long run, as it's ultimately going to be working to extract the same amount of moisture from the space regardless of whether it's doing it over a 24hr interval or a 12hr interval.

Sibley brings up some excellent points - the best way to reduce its run time is to keep unwanted moisture from getting in where possible and the second best way is to make sure you're using the right size unit. You should also make sure that you're cleaning the filter regularly and once every year or so, blow off the coils and fan with some compressed air if you can.

As for the grow tent - that's definitely going to make it run more frequently. We hang 90% of our laundry, including in the basement if the weather outside isn't ideal for line drying. When the laundry is drying, our dehumidifier is running almost constantly. The grow tent is probably doing the same in your space. I don't know that the cost of running another outlet would be recouped by moving the unit, you could try and run it off a good quality extension cord for a few days (and no more) further away from the tent to see if that reduces its runtime.

But ultimately a couple extra bucks a month of electricity usage is an excellent tradeoff in preventing mold and keeping whatever is stored in your basement smelling decent.

[catccc]

Thank you both.  @Sibley just to clarify, you are trying to raise it to 40% in the winter but it doesn't get there, correct?

We also have hot and humid summers and cold dry winters here in PA.  It does get pretty dry in our house in the wintertime, I have assume the basement will follow suit.

It makes sense that I should focus on preventing humidity to the extent possible if I want to run the dehumidifier less.  When we bought this 1929 home last year, our inspector was talking about leaking and humidity in the basement precisely noted "Some people dig a hole in the ground and call it a well.  And others dig a hole in the ground and call it a basement."  That said, there are a couple windows we could probably caulk around, for starters.  There was some leaking in the basement when we bought the place (almost didn't buy it because of that, actually) and we've since addressed most of the issues.  We probably could still use some grading on one side of the house.  It may be that we've done enough to keep water from infiltrating the basement, but there still could be excess moisture in the walls.

[snic]

The basement in my previous house was always musty-smelling and mold would occasionally grow on wood and cardboard surfaces. I got a dehumidifier and set it to 70% and that took care of the problem. While it's true that people prefer it to be less humid, if you're not living down there you don't need it to be down to 50%.

That said, the EPA recommends the humidity be no more than 60% - but that doesn't mean it actually has to be that low in order to prevent mold growth in specific cases. You could try raising the setpoint and seeing what happens - it won't kill you (immediately) and you can always lower it again if you start to smell or see anything.

[Sibley]

The reason I can't get RH to 40% in the winter is I don't have humidifiers going that are capable of it. I have a whole house humidifier but it doesn't work. Getting that functional would probably handle it. In the meantime, I don't use the bathroom fan much in winter and I have a small room humidifier.

Proper equipment is key.

[Villanelle]

I found that 2 smaller units worked better than 1 large one.  (I borrowed a large one from a friend for a time, to test my theory.)  My supposition was that 1 unit ran until the air immediately around it was dried out, then would shut off until the damp air on the other side of the basement eventually mixed, then turn back on again, and repeat.  One large unit just did that more quickly, but that almost made the problem worse because there was little mixing of air during the short times it was running.  Two units on opposite ends of the basement didn't rely so much on circulation of the air to get everything dried. 

Alternatively, a fan could help somewhat. 

But like Sibley, in my home I fight against humidity in the summer, then battle dryness in the winter, running humidifiers in family room and next to the bed just to prevent headaches and nose bleeds.  So you may not have this problem again until summer returns.  I have a whole-house humidifier that doesn't seem to do much (though maybe it would be worse without that).  the individual units just change things in small areas, but if placed strategically, it's enough relief to prevent the worse symptoms. 

[chemistk]

I found that 2 smaller units worked better than 1 large one.  (I borrowed a large one from a friend for a time, to test my theory.)  My supposition was that 1 unit ran until the air immediately around it was dried out, then would shut off until the damp air on the other side of the basement eventually mixed, then turn back on again, and repeat.  One large unit just did that more quickly, but that almost made the problem worse because there was little mixing of air during the short times it was running.  Two units on opposite ends of the basement didn't rely so much on circulation of the air to get everything dried. 

Alternatively, a fan could help somewhat. 

But like Sibley, in my home I fight against humidity in the summer, then battle dryness in the winter, running humidifiers in family room and next to the bed just to prevent headaches and nose bleeds.  So you may not have this problem again until summer returns.  I have a whole-house humidifier that doesn't seem to do much (though maybe it would be worse without that).  the individual units just change things in small areas, but if placed strategically, it's enough relief to prevent the worse symptoms.

Two smaller ones is a more efficient way to dry the space but probably more energy intensive overall. I did forget to mention that we have an oscillating fan running 24/7 in tandem with the dehumidifier. When we implemented that, our unit stopped running as frequently.

One thing to consider is to hang-dry your laundry in whatever space you are normally running your dehumidifier. In warmer months, I do our laundry all in one day (about 8 loads), but in the winter it's spaced out over the week which means there's usually laundry hanging to dry and although it's not a perfect solution, it certainly helps keep the humidity in the house a bit higher.

[GilesMM]

You need 1) data and 2) control.   

For data, I suggest a humidity sensor.  There are assorted options online that will report the humidity in your basement every minute or so and store the data for review. I like Sensorpush https://www.amazon.com/SensorPush-Wireless-Thermometer-Hygrometer-Android/dp/B01AEQ9X9I?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A3FMIYHRLE9HNB. I use them in the house, refrigerators, freezers, etc.

For control, just put the dehumidifier on a smart plug.  Then test it at various running intervals to get the desired humidity behavior.  I run my for two hours four times per day.  It has it's own internal humidity sensor so during those two hours it may turn off and on as well.

[GuitarStv]

I have a variety of wooden musical instruments in our house, and use hygrometers and humidifiers/dehumidifiers to monitor and control humidity.

60% humidity in a basement is perfectly fine and won't cause any problems with mold (unless there are other issues going on, like seeping from basement walls).  Higher than 70% for long periods of time tends to be where you start to run into issues.

In the summer, our basement tends to want to naturally sit around 65-70% humidity.  I run a dehumidifer overnight to knock things down to 55ish by the morning.  Then it'll slowly climb over the day back up to the mid 60s.  I've had no problems at all with humidity, moisture, or musty smells by doing this.

[catccc]

Thanks all!  We do have a hygrometer.  I think part of what I struggle I am not sure what the desired humidity is, and for how long.  Some people say 60% is fine, some people say it needs to be at 50%.  And for how long?  I guess that depends on how high it creeps up when the dehumidifier isn't on.  If it gets to 59%, maybe that's okay.  If it is any higher, maybe not?  IDK.  I'll play around with the equipment and collect some data, I suppose.

[Villanelle]

Thanks all!  We do have a hygrometer.  I think part of what I struggle I am not sure what the desired humidity is, and for how long.  Some people say 60% is fine, some people say it needs to be at 50%.  And for how long?  I guess that depends on how high it creeps up when the dehumidifier isn't on.  If it gets to 59%, maybe that's okay.  If it is any higher, maybe not?  IDK.  I'll play around with the equipment and collect some data, I suppose.

I just set mine at 60, and then didn't turn it off.  It cycled on an off as needed, so it never got above 60.  Otherwise, I'd have had to lower it to probably 50 so that it didn't get much above 60 during off times. That seems less efficient than just letting it run as needed (assuming your's has the ability to set a desired humidity and then regulate itself, as opposed to just a binary on/off).  With 2 of them in the space, both set at 60, I doubt any area got much above 60 or stayed above 60 very long.

[GuitarStv]

Thanks all!  We do have a hygrometer.  I think part of what I struggle I am not sure what the desired humidity is, and for how long.  Some people say 60% is fine, some people say it needs to be at 50%.  And for how long?  I guess that depends on how high it creeps up when the dehumidifier isn't on.  If it gets to 59%, maybe that's okay.  If it is any higher, maybe not?  IDK.  I'll play around with the equipment and collect some data, I suppose.

60% is totally fine.  When humidity gets up into the 70s you start to run into problems (wood will swell and sometimes warp) and it's more likely that you'll get condensation on walls if there's an abrupt temperature swing.

[catccc]

Winter update!

I had a kill-a-watt hooked up to the dehumidifier and the unit hardly used any electricity over the course of a few days.  We moved the hygrometer out of the grow tent, and the humidity in the basement was consistently low.  Sometimes in the 30s, and we even saw the teens.  So we decided in the heating season, we probably don't need to have it plugged in.

I'll concede that 55 is probably a fine setting.  We still need to caulk and such. 

[GuitarStv]

Winter update!

I had a kill-a-watt hooked up to the dehumidifier and the unit hardly used any electricity over the course of a few days.  We moved the hygrometer out of the grow tent, and the humidity in the basement was consistently low.  Sometimes in the 30s, and we even saw the teens.  So we decided in the heating season, we probably don't need to have it plugged in.

I'll concede that 55 is probably a fine setting.  We still need to caulk and such.

Our basement drops well below 30% in the winter due to central heating and the associated humidity drop.  You will likely only need to run a dehumidifier during the summer.

[Sibley]

Yep, this is very common. Keep an eye on it however, especially if it warms up and is damp outside.