1) welcome
2) you should add some pitch to the roof as others have said
3) my solution was to buy the clear hurricane panels and i lay them across the roof of the lath house in extreme cold.
4) reconsider the way you are potting the orchids so that they can handle our rains. This is not possible if you do not have the time and energy to water them when you have to but i have LOTS of orchids that simply COULD not be over watered because of the media i use and the mounts, etc.
5) i respect the rate at which you are growing your hobby...

---------- Post added at 09:43 AM ---------- Previous post was at 09:38 AM ----------
this is one of my growing areas (where i would use the panels if needed) from last week in the middle of the endless rain.
you can see that while some of the back plants are under the eave, most are just getting soaked...as long as they get adequate air as well AND IT IS NOT COLD (that is a huge caveat i rarely have to consider) they like a lot of water
Bulbophyllum Medusea by
J Solo, on Flickr