I went to Wally World the other day and came back with a Weather Channel Wireless Temperature Station for $24.95. I mounted the transmitter in my coop on the back wall above the Gals' heads. My coop is about 75 feet from the house but this unit transmits up to 300 feet. It uses two AA batteries in both the transmitter and the receiver. The receiver is mounted on a wall in the kitchen. It works great. We had temps down below 25 F on Sunday but the coop stayed above 35 F. This weekend we're going to do some insulation with sheets of foil backed styrofoam from Lowes. They're about $10 a sheet and it'll take three 4x8 sheets that I can cut into any size I need with a razor. The sheets are an inch thick. The label on each one says it'll provide an R5 factor when it's installed. We'll put it in all the walls, ceiling, and underneath the floor. I'll use Liquid Nails to adhere it. We'll also do some molding with that sticky foam rubber stuff around the doors to seal off any drafts. When I built the coop my Wife did a great job of sealing up all the joints and openings with that expanding foam stuff. Now if that doesn't keep them warm enough then I have one last trick up my sleeve. We have a bunch of river rock about the size of potatoes that I'll heat up in a 500 F oven and put them in a wooden box with a lid and vent holes. That'll go out to the coop over in the corner away from the roosts on those really cold nights when it's really needed. And if that's not enough, well I've already spent a small fortune on the coop and run so I might just go ahead and ship the gals off to Bermuda or somewhere warm.