Vandas and Ascocendas have a higher light requirement than most other orchids.
In South Florida, we grow our Vandas in an unobstructed area (i.e. there are no trees or buildings to block the sunlight).
We also cover our grow houses with 60% screen in the summer and 50% screen in the winter. We find this style of growing allows us to maximize our total daily solar radiation. A foot candle reading of 2,000-4,000 ft candles under shade is best. A foot candle meter can be purchased online.
Do you have questions about how to construct grow houses to maximize your total daily solar rays? Ask us here in the comments!