I do not recommend heat lights for full grown and fully feathered chickens in the winter. Back in the good ole' days chickens did not have heat lights like they do now. I know for a fact that a lot of you are in areas where the temps are lower than ours here in central Texas and your chickens are handling the weather just fine. Chickens don't mind the cold but they do mind drafts and the rain at night so these are a top winter priority for them. The chicken coop, or house, needs be tight enough to keep the cold wind from blowing through the walls. I recommend that all four walls are to be made of wood or some tin and wood. Ventilation should be above head height and there should be no drafts coming through the coop. The waterproofing needs to be checked and any areas that are dripping water into the housing need to be sealed quickly. Wood should be used for roosts and they are never made of metal poles or plastic. Wood roosts will help to keep your hens feet warm whereas metal or plastic will stay cold all the time and cause their feet to become too cold. Imagine stepping on a sheet of tin with your bare feet in the winter and then having to remain there for hours. Some sort of litter such as straw should be used inside the coop and around the coop. This will help by keeping the hens feet off the frozen ground while they scratch around during the day. The entrance to the coop will become muddy and frozen if no bedding is put down. This can make the hens reluctant to come out during the day. Keeping the straw clean is important. Rake out and replace what becomes soiled or wet. I also add hay, leaves, and other types of clean mulch's deeply layered (a foot deep or deeper) into the bottom of my hen houses. When I feed them on cold mornings their coops are very warm. The deep mulch heats up the coop. Try it it really works I swear by it. I have never had bugs or mites because of it either. There will be crickets or rolypoly bugs but the chickens love the deep mulch and scratch around in it for the bugs. I learned this from a college professor with yard birds who lives in Bastrop, Texas. She did leave a radio on for her chickens which was cute. I guess they lay better with country music playing. I try not to let my hens get wet before a freeze due to rain if I can help it, and I keep them out of chilly winds, again if I can. A day like yesterday which had a wind chill factor I did not let them out of their houses. I imagine there may be extreme cases for heat lamps but then you will always have to use it. I did the light thing before and it backfired when those same birds had a very cold night without their heat lamp. I did not keep track of the weather and they were all looking pretty miserable the next morning. I guess I learned the hard way. I have a web site that has articles about mulching, gardening and the other benefits of poultry. Its all good stuff that I learned from people like yourselves with birds.