Greenhouse Humidifier

Clif, most devices need to be hooked up to a water feed so that they don't run dry after very long. If hooking up to a garden hose is the main problem, you can get around that by hooking up a 1/4" tube feed line from the nearest sink by adding a simple valve that doesn't need to be installed by a plumber.

I own three devices suitable for greenhouse humidification:

Aquafog 400 I have had this for 5 years. It really effective, needs no maintenance and is probably about 30 decibels when running. However it needs at least 8-10' of clearance so that the tiny droplets can evaporate without condensing on obstructions such as foliage. If you have a high ceiling it could work in your 8x10' space, otherwise it wouldn't be practical. It is excellent, however for a lath house because it has considerable capacity to put out moisture in to the air, combating the dryness of more open spaces than other humidifiers can. The output is adjustable from very small droplets to large droplets.

Hydrofogger (Minifogger Humidifier)
This is a great product and have only had it for 4 months. It's pretty quiet and puts out a nice fog with medium-size droplets. It needs clearance of at least 3-4' so that the tiny droplets can evaporate without condensing on foliage. I think this would be the best of these three for your space.

Trion Herrmidifier 707 Atomizer This has some faults and in my experience, isn't very friendly for the consumer wanting a "plug n' play" device as one will need to make adjustments to it before being able to use it. It isn't quiet at all but the real advantage of this device is that the water droplets are super-fine. It only needs 1-2' of clearance. I have had mine for 14 months.

 

the best greenhouse humidifier is more plants.

 

I've had and used a hydrofogger for years and love it. But, unless you have good water, the heads will clog or put out a white coating on your plants. Mine runs off my R.O. for this reason.

 

An electric valve plumbed to your live water supply, operating a mist nozzle manifold, and wired to a humidistat. As Candace mentioned, you need to have good water (low TDS) or you'll have stalactites and stalagmites in a couple hundred years. Array the mist nozzle manifold under your benches.

 

Exactly what I have and it's magnificent. The solenoid valve is from Grainger. I oriented the spray directly against concrete block bench legs & they disburse the spray into a fog. I operate at about 100 psi with 0.012" nozzles.

This is where I went wrong the first time - I had them overhead & everything got wet.

 

I have the Hydrofogger (the larger of the two models) and absolutely love it, the humidstat works real well too.
Also, if have the height you can remove the Directional Fogging head.
The fog will go up and diffuse into the air rather quickly.
It seems to put out even more fog since the fog is not hitting the head, condensing and draining back into the fogger. The fans you have in your GH will help diffuse the moist air.

On days that are going to be especially hot and dry I will go in and manually turn it on by cranking the humidistat all of the way on for an hour or so first thing in the AM.
With it being cooler in the AM, the fog really fill up your GH and some of the moisture will condense on your plants (bulbos especially like this) and give them some moisture before the hot dry day.

The moisture collects as very small droplets on your plants, but it does dry off pretty easily in an hour or two as the GH warms up. So you don't have to worry about rot.
They really seem to appreciate this extra moisture.
If you look at photos from where your orchids originate come from, you will often see the dense foggy conditions that they have, particularly in the morning hours.