No heat lamp in the plans for my birds, I'm in Michigan, its snowing right now and there's no hope of getting above freezing for a few days, and it's only November!
I am finding that I built my coop to nicely and sealed up (to make it 100% predator proof), because my humidity in the coop is WAY to high. Thank God I put a cheap temp/humidity gauge in there or I would have had no idea. The coop is 4x4 foot print, and about 4 high with a slanted roof, there are 4 birds inside, and I originally built it with vents at the top of 2 walls. Being winter and the fact that they are in the coop about 14-15 hours a day and pooping a lot more in the coop, the humidity was about 80%!! This past weekend I cut open each of the vent holes to about 2x as big as they were, added another vent on a 3rd wall, and added a small hole near the top of the 4th west facing wall. I am hoping that this helps, but the humidity gauge is still reading close to about 70%, which is still pretty high. I am thinking about switching over to sand bedding in the coop so that I can sift the poop out daily and quicker without removing so much bedding each time ($$). This is my first year/winter with chickens, so I'm adjusting the coop, bedding and venting as I go to meet their needs.