I've been letting them out in the run most days, as it's only gone down to about 16 or so here and their body heat usually keeps the henhouse in the mid-20s even when the pophole is open, so they can have their choice.
However, last night it was down to around 0, and I was worried. The temp in the henhouse (with it all closed up) was down to 16. I just brought a heat lamp out and now its back up to 22 in there, but still about 6 degrees outside. I decided not to open the pophole until it gets well into the teens outside. I noticed a teensy bit of white tips on Rita's comb, presumably frostbite, and I am feeling guilty. I know that these breeds are SUPPOSED to be hardy in this weather, but I still feel bad!