Rustyswoman,
Mine are in a 8' by 30" plywood box,which is also 30" high, with a hardware cloth top, which I keep mostly covered with old rugs and blankets. There are open squares for ventilation. I also wrapped insulation around the outside of it, so it can sit up next to the house on our screened porch, which is on the north side of the house. It got down to 28 last night and the brooder temp by the red bulb was 90 degrees- most of them were NOT underneath it, in fact many of them spend their time by the 150 watt white light at the other end, playing and eating. They are four weeks old tomorrow, I think, and not completely feathered out. I was hoping to put them out at the end of next week, but Superchick is way behind in feathering, and I will wait for her/him - hence the new Plywood Palace, the two lights and all the space in which to choose comfortable temps. I don't notice the dust out there, but they spent two days in my piano room two weeks ago, when the temps hit 18, and I STILL have dust to deal with, after cleaning twice- I think it swirls up in the air and settles back down when I clean!!!
Since it is winter, I will probably still put the red light in the little coop when they move.....for their night time use, at least. It has been a nasty, wet fall, and so maybe I will just leave it on, I don't know. I hate the idea of them being wet and cold even if they are feathered out! My babies!!!!