In my opinion, the T5's that are sold at Home Depot or Lowes are not that sufficeint for the lighting needs of many high light orchids like Cattleya. Check out this website:
Buy T5 Fluorescent Grow Lights. They have great prices and quality light fixtures. I have a New Wave 2ft 8 bulb fixture. Clearly by looking at the link I provided the 2 ft bulbs are not as strong as the 4 ft bulbs, so if you have the space get the 4ft light fixture. Also check out Ray's website for inexpensive but good quality T5 lights as well. That is were I am planning my next purchase from....the quality is very similar to the New Wave brand and his prices are much cheaper...here is a link to his website:
https://www.firstrays.com/cgi/cart/c...exact_match=on. Hope this helps!