What a gorgeous coop !!!!!!!!!!!!!!!!!!!!!!!!!! With the coop remaining that warm in winter, the Eco Glow may be fine for keeping the chicks warm. However, how do you keep it that warm and also maintain adequate ventilation? I have all of the windows open on my coop year-round, and only partially close them when it's below 0 degrees F.
As to whether the buff orpington will accept the chicks . . . it depends. If she has hatched and/or raised chicks before, then it's highly likely she would adopt them. If not, it really depends on the individual hen. Buff orpingtons (as a breed) tend to have a good reputation for being good setters and mothers, but that varies by individual. My only "homicidal hen" was a buff orpington; she was a good setter but attacked/killed foster chicks. She was super-defensive when she was broody, and I've been told that this sometimes indicates a hen will turn on chicks. Again, so much depends on the individual hen. My australorp is a great mother with great personality.
It's certainly worth trying if the broodiness and arrival of day-old chicks coincides. Alternatively, you could wait until she's broody and then order chicks so they arrive after she's been broody for 2 1/2 or 3 weeks.
If this doesn't work, the coop certainly looks large enough to set up a "safe safe" for the chicks with chick-sized doors to allow for early integration.
