I am waiting to incubate chicks till it warms up a bit. My brooders will be outside. I have a "barn" the front of it is open so there is lots of air movement. and it is as cold as the outside temp I can hang a tarp over the opening. but there are cracks between the boards so it is not gonna be air tight. I have a couple choices for brooders Large rubber maid bins or wire dog kennel enclosed with card board. I do have Styrofoam insulation I could cut and put on the outside of the card board for warmth. the chicks can not be in the house do to allergies. How cold can it be outside with a 250 watt bulb? I dont want to incubate and then just loose the chicks to cold.