Do you add water to the base tray or use it just to catch the water when the orchids are watered.

I have the bottom tray filled with water. I also have added some 'mosquito bits' to the water to keep mosquito's out. The humidity stays about 30% on the low end and up to 80% or so on the high end even though they're in a greenhouse and it gets pretty hot in there. They also help keep the temperature down around the orchids.

Thanks Chris. Would this be just as effective in the home?

I don't see why not. And you don't have to make them so big if you don't want to as long as you can find a top try that fits.