Dehumidifier: Helper or Energy Hog?
 

I recently inherited a free-standing dehumidifier and gave it a whirl.

The control knob is roughly calibrated to ambient humidity, and it has a low/"quiet" fan speed selector.

It's hooked up in the basement and drains into the sump well. The knob vs. a humidistat shows 60-70% humidity, but no fogging of windows or dampness is noted.

So, is this thing a good supplement to reduce the burden on the Central Air system, or just a device for musty, damp basements?

RH77

i have mine 65-70% installed in the basement. that thing gives off lots of heat but keeps the basement nice. it used to be at 50% but it ran a lot more and heated the basement up in summer, dryer but hotter( no ac down stairs). that keeps the moisture off the elec box, that keeps corrosion down inside the box too. and i think it helps lower any mold growth too.

The following is not really related, but I feel that it needs to be said anyways.

My dad built our current house using a poured styrofoam basement. In other words, a company came in and built a foundation out of, yep, hollow styrofoam. After this was complete, they continued to pour concrete into said styrofoam. The result was a warm basement in the winter, and a cold basement in the summer... with our without central A/C or heating. All of this in Michigan. Oh, it is a walk-out basement with lots of windows (that have shades for the summer months).

To tie this in with the OPs question, we have NO humidity or condensation whatsoever. Our previous house, with a traditional poured concrete basement was (if my memory serves me) always damp, pretty much year round.

Point being: make your basement from styrofoam and you will never have to worry about humidity problems again!

idk this would help me alot if somone knew for sure because i have mine running right now. it helps but it does seem like it would use a lot of energy

I ran our dehumidifier this summer for a couple of weeks after we had a lot of rain and some rain managed to get into the basement. It ran almost 24 hours a day, and drew about 300 watts, but made the basement warm faster than it made it dry. It also increased our electric bill for that month to the highest it has been for years. I thought that something had gone wrong on the place, or there were lights on somewhere that I didn't know about, until I put the Kill-A-Watt on the dehumidifier and found out what it uses. And, due to power factor, it uses over 500 volt-amps, which affects the actual power usage from our battery/inverter system.

I think that a small air conditioning unit might be a better choice, for someone buying new, as an A/C would cool as well as dehumidify, and you usually use the dehumidifier in the summer when you don't really need the heat from the dehumidifier.

We were lucky and had a few nights of below average temps that were also dry, so we opened 2 basement windows late at night and ran a fan to circulate dry cool air to dry out the basement and cool down the root cellar.

My parent's house has a walk-out basement that's finished inside. Guest bedroom, living room, bath, more.

Always was damp as heck there. Always had a demidifier running which helped noticeably. Was quite cool even with it running.

In their case it's mostly a condensation problem, since the walls were always quite cool and the air is damp in that locale. Not a seepage probem in their case.

They redid the bathroom with styrofoam applied to the exterior walls, then wallboard and wallpaper over that. This helped that room a whole lot. Moral of that story is, if you have a moisture problem in an existing basement, consider styrofoaming all the walls before you think about dealiing with the floor.

We have 2 dehumidifiers in our basement. It isnt damp down there, but I have a classic car I like to keep from rusting and it keeps the wooden French doors from swelling and creating shutting issues..

Those darn classic cars!! We are working on putting radiant heat (solar heated hot water of course) in the floor of part of our existing pole shed so we have better storage for the 1971 Honda N600 and the 1965 VW double cab pickup. Maybe not what my generation usually considers classic cars (I think more of Packards or other huge majestic machines from the 1920s or 30s), but I am sure a younger generation will consider them classics.

Of course, it will provide heated workshop space, too. I like the idea of low intensity heat to keep things dry instead of the refrigeration system of a dehumidifier, but heating the basement floor in the summer to keep it dry is counterproductive if we also want it reasonably cool.

I keep one in my gun room, guns+rust=bad Not real concerned about the cost there...

I run a dehumidifier in my house and keep it as dry as possible. Last year was the first year I ran it and my gas bill was lower than usual, part of it was the dehumidifier generated some heat but most of it was because drier air doesn't pull heat out of your body as fast as damp air so I was able to run the heat at a lower temperature without feeling the least bit cold. I don't run it in the summer and just leave all the windows in the house open with fans so it won't help in the summer. In the winter though it is noticeable if I forget to dump the water out and it is off for 12 hours or so, the house feels colder and uncomfortable. I keep it set at 30% in the winter and it runs for a week straight to get the house down to that in the winter to start with then it cycles prob 75% of the time running.

De-Hue
 

A dehumidifier has the same mechanics as a window air conditioner, I used to work in the HVAC and Appliance industry and I had repaired many of these units. The auto drains are nice, some you have to empty the water bucket every 4 hours. One thing I looked for was where is the humidity coming from, do you have a sump collection pool? They have a cover that has a low voltage fan that blows air out a duct to the outside. Thses little things have helped allot when you can isolate the water source. Some of the older houses have French Drains that are like gutters running next to walls and collect in one corner of the basement. If a foundation is old, try what ever you can to seal the walls, the main thing is to keep the water from being exposed. I have seen allot of basements with carpeting, my basement has a sealed and linoleum tiled floor, I use area rugs to help. If a basement just has concrete, some sort of sealer needs to be used. Its kind of like building a boat from the inside out. Little tricks like installing vent louvres on the basement door to keep air moving can also help.

Hope the ideas help.

De-Hue
 

A dehumidifier has the same mechanics as a window air conditioner, I used to work in the HVAC and Appliance industry and I had repaired many of these units. The auto drains are nice, some you have to empty the water bucket every 4 hours. One thing I looked for was where is the humidity coming from, do you have a sump collection pool? They have a cover that has a low voltage fan that blows air out a duct to the outside. Thses little things have helped allot when you can isolate the water source. Some of the older houses have French Drains that are like gutters running next to walls and collect in one corner of the basement. If a foundation is old, try what ever you can to seal the walls, the main thing is to keep the water from being exposed. I have seen allot of basements with carpeting, my basement has a sealed and linoleum tiled floor, I use area rugs to help. If a basement just has concrete, some sort of sealer needs to be used. Its kind of like building a boat from the inside out. Little tricks like installing vent louvres on the basement door to keep air moving can also help.

Hope the ideas help.

I use my dehumidifier as a "space heater" in the winter...
 

And if you follow through what that actually means, you discover the (somewhat surprising) fact that a "dehumidifier" is actually more energy efficient as a "space heater" than a real (electric) space heating unit is! Obviously this works against you in the summer (often the lower humidity is more than offset by the heating of the room it does), but can actually work in your favor in the winter (as it will both make your house less humid/dank and heat the room the unit is in). Here's why that happens:

1) Like the vast majority of electrical appliances, virtually all the watts used to power the dehumidifier also produce "waste heat" that is almost identical (in heating ability per watt used) as a normal (electrical) "space heater". A normal space heater is generally smaller (and a little more quiet), and also generally produces more heat (but at the "cost" of more power used). But watt hour for watt hour, the energy used to power your "dehumidifier" heats about as well as a "space heater" will. And this is true no matter how fancy/expensive your space heater is, as virtually all of them generate their heat by simple electrical resistance (which is the same principal that produces this first portion of "waste heat" in the dehumidifier).

2) In addition, there is heat generated (which goes into the heating of the room) by precipitating water out of the air. In the case of a traditional dehumidifier, this takes the form of heat on the "hot" side of the "heat pump" (remember both dehumidifiers and "air conditioners" are "heat pumps" that move heat from one place to another), that is necessary to generate the "cold" used (by the dehumidifier) to precipitate the water out of the air. Since this heat is proportional to the amount of water precipitated out, the more "efficient" your dehumidifier, the more "bonus heat" you get for the power used. So the more energy efficient your dehumidifier is at lowering humidity (its "primary task"), the more energy efficient it is as a "heater" as well (as the more water you precipitate out, the more "heat" you generate from that process).

3) Therefore, while they are physically a lot bigger (and a little more noisy than a "space heater"), a dehumidifier is actually a more energy efficient electric "space heater" than a real "space heater" (because a "dehumidifier" gets heat from both sources, whereas a "space heater" only gets heat from the 1st "resistance" method). So if your goal is to "cool", a "dehumidifier" may actually work against you (as it will often heat the room more than it will improve comfort by lowering the humidity level).

OTOH:
If you were planning to use a space heater anyway, a "dehumidifier" may be a better choice. A "dehumidifier" is physically bigger, and a little more noisy than a "space heater", and they do remove humidity from the air (which might be a problem if your air is already super dry), but they are more "energy efficient" heaters as well. And (in my neck of the woods) natural gas prices generally skyrocket in the winter (our central heater is gas), but electric prices have remain relatively stable throughout the year. Furthermore, we find we really only need to heat up a limited number of rooms (for example, our master bedroom), and so running the central air is costly (as it heats all the rooms in the house). As a result, I've found we can actually lower our utility bills a lot, by setting our central air lower, but then putting a limited amount of electric heat in some key rooms. And given that little fact, we found that using our "dehumidifier" as one of the key "space heaters" (in the master suite), actually worked better (and used less energy) than going with a "real" space heater....

BTW: If you were wondering, the reason we had a "dehumidifier" in the house, was due to allergies. I'm very allergic to dust mites, and those things breed like wildfire when the humidity gets up too high. But if you can get the humidity down sufficiently, they virtually all die off. So in my case, lowering the humidity level a bit in the winter, actually is beneficial to my health (in addition to any efficiency that the dehumidifier is as a "heater").