I insulated my coop.
It is not closed up all winter, just on the nights like tonight that dip below 0 degrees, because ventilation is important. I also bought one of those indoor outdoor thermometers and put the sensor inside the chicken coop, so from the comfort of my home, I can tell you right now it is 8 degrees outside and 36 degrees inside the coop. That is nice because I do not have to run out and check the birds.
Because of all that, I don't have a problem with water freezing, but the insulation is an investment. But the Return on investment is quick; when it gets cold the birds eat a lot more grain, and at $15.00 a bag, it is about the same as a roll of insulation, and it only took a few rolls to completely insulate the coop, so by Spring I will have recooped my insulation investment...pun intended...just from the savings on grain.
My egg count dropped off when it got cold too, which is not a problem you have I know, but now that it is 40 degrees in there, and with a light on a timer for 14 hours, the ducks/chickens do not know it is not Spring so they have been pumping out the eggs. Those extra eggs also makes up for the cost of the insulation.
It takes a sharp pencil to farm today, but I always try and justify what I do with solid numbers. The cost of insulation divided over the age of the hen house is actually very low in comparison to extra labor, increased grain consumption and lower productivity.