I've added a second row to both of my grow windows as the addiction gets stronger
I live in a mild climate so windows are often open and the humidity mostly stays above 50. Winters can be cold and rainy, but that does help keep humidity up if furnace comes on in the morning. There is even a little microclimate in the monopod window because it's set back about 10-inches. Lower bottom shelf in back has about 10% higher RH than top shelf. Great for the Aergs.
Here they are:
2nd Floor Cattleya Window by
Gardentheater, on Flickr
1st Floor Mostly Monopods Window by
Gardentheater, on Flickr
Also added additional lighting. The shade tree is growing.