I don't know how high your roost is, but I highly recommend a ramp for the bigger girls because it can be hard on them to jump down from any bit of height. I have a big BA who very carefully walks down the ramp every morning while the smaller girls just jump down. It's like she knows she's too big to be doing that! Love that girl.... my big broody mama
I've used plastic house wrap the past two winters, of course I have no recollection of what mil it was.... but it held up great in the winter winds! I got it at menards. The only problems with it was that it was kind of a pain to put up and it was noisy when the wind blew. This year I'm trying the clear plastic corrugated panels. They're easier to put up and can be reused from year to year assuming they don't shatter when it's -25 and windy...