I agree with Chris, the idea of rats in your coop is definitely one less thing to worry about, Sue! I think Mollteaser's sad story was more probably caused by a weasel or similar. Perhaps the main focus of all our efforts has to be to keep the blighters out of the run in the first place, and this means a really secure edge all round the bottom of the run, with mesh too small for them to get through, (ie 1/2'', at least one layer round the bottom of the sides, plus underfloor mesh at least round the inside edges, if not all over.)
I think if your run is safe, a greater danger to your hens would be to reduce the ventilation, Sue, because the less ventilation you give, the more condensation you'll get. With 4 full-sized hens in the same sort of house as your 2, I never get condensation, but with night time temperatures well above freezing so far, I do leave the vents and pophole open, and also change the damp paper bedding daily of course.
I think if your run is safe, a greater danger to your hens would be to reduce the ventilation, Sue, because the less ventilation you give, the more condensation you'll get. With 4 full-sized hens in the same sort of house as your 2, I never get condensation, but with night time temperatures well above freezing so far, I do leave the vents and pophole open, and also change the damp paper bedding daily of course.