Dehumidifier: Helper or Energy Hog?

[GasSavers_Scott]

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.

[GasSavers_Scott]

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.

[DracoFelis]

Originally Posted by Scott

A dehumidifier has the same mechanics as a window air conditioner,

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").