Life is Good! :
I've used those ceramic bulbs for our box turtles and for our iguanas.
What I learned was to REALLY MAKE SURE that the wattage on the bulb matches the wattage on the fixture that you use. I've burned out a fixture using a bulb that wasn't rated for it. Thankfully, it simply blew the fuse - not burned the tank or anything.
I've also learned that it's kind of hard to regulate (in a closed environment like a tank) the level of heat emitted. Chickens, being more mobile, would likely find their 'comfort' zone under or nearby the fixture. They really do give off quite a bit of heat.
Perhaps (when it's a tad cooler), you could set it up in something like a small bedroom or bathroom, and measure the level of heat at various points (starting temp, after 1hr, after 3hrs, after 6hrs, etc.) - that way you could see what the bulb would offer.
Good luck!
I am thinking of using it in the fixture for using a heat lamp, that way it's enclosed , I am thinking 125, I don't want it above freezing in the coop but high 20's would be nice. Thanks for the replys