Any photos of your coop/run and flock?
There are many factors to consider for winter time flock care.
Each of us do things differently and it really all depends on how your set-up is.
For me, I open the pop door and let them decide if they want to come out or not.
Most of my run is covered and dry, so having wet feet is usually not a worry. I too have heat (light bulb in a cinder block) under the outside water station, but usually I put warm water in it first thing in the morning.
Chickens need a lot of water in winter, so if you don't let them out, then make sure they have access to water. If you place water indoors, check for any wet bedding and remove it promptly, moisture in a closed up coop can cause frostbite as well. A winter coop needs to block wind, but have plenty of ventilation to move moisture up and out.
Having some type of wind block outside is a good idea. Chickens can stay warm, if their feathers are not blown around too much. A wind block can be a simple as a couple of boards propped up for protection, to wrapping areas with plastic. I found some scrap underpinning and attached it to the backside of my coop to block most of the North wind. It's not pretty, but does a good job.
Here is a really good, comprehensive article that give you some tips on frostbite, treatment and tips for prevention and cold weather care.
http://www.the-chicken-chick.com/2013/12/frostbit-in-backyard-chickens-causes.html