So, even though this post was originally meant to find out more about orchids on west facing windows. We finally moved into our loft and discovered that we're actually facing NW. We have unobstructed views of the skyline but a building to the left blocks the sun from the west, so I actually don't think I might need to worry about temperature at all.
Using Photone (which has worked great for me) I measured 173 ppfd at 1pm, I think this spot might be fine for my Phals without need for supplemental light. I will probably need to move my cattleyas to shelves under artificial light.