I've built this brooder for about zero dollars, it's 2'tall and 4'long, 20"wide (an old wardrobe box). I elevated the heat lamp in a 12x12" enclosure I call the chimney. The top is covered with an old mesh screen. The box is divided with heat on the right and sunlight on the left. I figure the temp variations are ok since the hens can travel closer or further from the lamp, but I'm trying to stick to the 5°/week rule. It's in the garage (not heated, but closed most of the day. I wonder if I need to cover the screen and block the sunlight in order to further prevent drafts, or are 2' walls enough?