How does a humidity controler work? Are they worth the extra money?

I was wondering how humidity controlers work and if they are worth the extra money? What kind of fans and ducting do I need to use a humidity controler? I watched a few grow videos and there duct systems have these big boxes that contain their air pump/fan that go with there little control dial, and the whole thing is seeming a little over whelming, because I need to do this right, but also for as little money as possible. So I'm trying to buy the parts I can for cheaper at Home Depo, but everything seems to be incompatible, but only because the Hydro places want you to pay their mark up.

So PLEASE HELP, as I'm just not sure what direction to go in.

If you're just starting it's probably overkill. You can manage humidity quite well with just a fan and timer IMO.

I'm a little past beginner and want to ensure success with my new grow space, as it is going to be quite an investment for me, and I don't want to build this room twice, or spend more in the long run. Like someone said on an other thread, buy once so you only have to cry once. So any info on humidity contol systems would be great.

So what you are saying OGEvilgenius is if I have a hydrometer to check my RH, I can keep a consistant RH just by reducing or increasing my exhaust useing a dimmer switch on my in line fan? What kind of a humidification system do I need? As I am in a very dry area, and am sure I will need to add humidity at least to the Vegatative half of the room.

If you are in a really dry area I'd look into those swamp coolers for your chilling needs. Will help you with humidity. If you really wanna be serious about this I would consider sealed room CO2 injection.

A humidity controller just turns a device on or off when the humidity hits a certain point, just like a thermostat does for temperature. These can be used to control dehumidifiers or humidifiers -- of course, nowadays, most dehumidifiers have a controller build in. In most cases, you don't need one -- people generally have a problem with high humidity, so all you need is a somewhat modern dehumidifier. However, if you have problems with low humidity, they can be useful to control a humidifier, since these usually -don't- have controllers built in -- and from what you say, it looks like you might want one.

My flowering and veggy rooms will be sealed when complete. But how much Co2 will the/ Ohh I can set my ventilation on a timer to shut off during Co2 treatment.

What kind of results do you get with Co2. Seems expensive but easy to install at anytime.

I've heard that a 20% increase in yield with CO2 is something you can count on, if you've done it right.