In the coop, as they don't usually go into the run in the cold weather of winter. The size and type of lamp depends on your coop. If you have a small and insulated one, then you only need like a 40-60 watt bulb. But, if your coop is large (more than 100 square feet) then you need to have an actual heat lamp.Do I put the light in the coop or run ? And just a regular light or heat lamp ?