well where do you plan to keep your neps in the winter?
obviously they will need to be indoors somewhere..
just put them in that spot now! *[img]http://www.**********.com/iB_html/non-cgi/emoticons/new/smile.gif[/img]
you will only be able to grow neps that can live in normal indoor home conditions without special treatment.
Like N. coccinea or other "easy" hybrids.
there are several that can thrive indoors with no special treatment at all..just stick them in any window and away they go.
If you want to grow neps that need special temp and humidity requirements, like picky hothouse lowlanders, sorry..but you simply cant do it with the growing space you have right now.