I don't see that the wind matters. There is (well, there SHOULD be) no wind-chill indoors, which is where they'll be at night and if they feel too cold outdoors. What matters is the temp and the humidity.
In fairly dry air, with a well-ventilated dry coop and no other health problems, I really don't think there's much of a problem with single digits without heat.
If there is something about any of the chickens that makes you think they're extra prone to frostbite, or if your coop is a bit damper than one might ideally like for one reason or another, then some people would decide to err on the side of cautionary heat (others would just keep a close and frequent eye on things).
Good luck, have fun,
Pat
In fairly dry air, with a well-ventilated dry coop and no other health problems, I really don't think there's much of a problem with single digits without heat.
If there is something about any of the chickens that makes you think they're extra prone to frostbite, or if your coop is a bit damper than one might ideally like for one reason or another, then some people would decide to err on the side of cautionary heat (others would just keep a close and frequent eye on things).
Good luck, have fun,
Pat