Winter warmth for Phals.

[Dcchase]

Hi I've had a variety of orchids for about 5 years. But I only have been successful in getting them to flower in the past year. I have a question about temperature for my Phals. I have 10 Phals., 5 hybrid, 4 species and a mini hybrid. They have all done very well in front of a southwest window through the summer and fall. Now with the colder winter temperatures, unless it is sunny, this window spot can be quite chilly. I do have all my orchid trays on heat mats during the winter.
My question is whether my Phals. would do better where they are, in the southwest window with some chilly days or in a different spot under 3, 2'-T5 lights and on a heat mat. Under the lights they would be consistently warmer but have less light and little natural light.
Five of these Phals are in spike now and the spike growth does seem to have slowed with the colder weather.
I live in CT and have all my Phals. in NZ Sphagnum moss.
Thanks for any suggestions. Dcchase