I am a firm believer in giving a bit of help with a heat lamp if it can be done safely when unusual cold is present as they are not used to that kind of cold.
Many on BYC don't believe in supplemental heat but as for my pets I want them to not get frostbite. It is a sure thing that my chickens...
Six month old Orps will be fine in those temps as long as they are out of the wind (no breezes blowing on them - keep air vents up higher than their perches, for example). If you have them in something like a rabbit hutch you can put sheet plastic across the front or plexiglass (or plywood)...
I've had coops where the ventilation came from underneath. What I found was that in the windy cold winters if I just put some windbreaks around the bottom, say on the side where the wind was coming from, that it alleviated the wind coming into the coop. I didn't close the hole off, just a...
Here is what I do with my two shed coops in the winter (keep in mind here in the Pac. NW it is rain/fog, rain/fog, rain/fog most of the winter- if I go outside I can get soaked from the fog walking around my yard):
SHED #1- Metal shed with large fowl: uninsulated, condensation dripping...