Exactly how cold does it get in your area? I've been having 20 degree nights here the last month or so and my three Ko girls are doing better than most of my other bantams.
For birds as small as Kos, depending on how many you're getting, I bet an EcoGlow-type brooder would work great. I just got one for Christmas, the 20 chick model, but if it's raised to the highest level I bet it could easily accommodate a couple of Kos. I've already used mine to nurse a chilled chilled Cornish Banty roo back from the brink of death and he fit quite well under it. I'm sure a 50 model could fit more. And there's no chance of fire occurring with that type of heater.
It isn't clear whether you're talking about brooding baby chicks or keeping a coop heated for adult chickens.
If you are just talking adult chickens, heat isn't even really necessary. If you need to heat a coop safely, though, just taking the bite off sub-freezing temps, I recommend an oil-filled electric heater, economical and safe.
If you need to heat a brooder for baby chicks, I highly recommend the heating pad system. It's both safe and inexpensive, while being very dependable and beneficial for developing chicks. See the thread on the "Raising baby chicks" forum: "Mama Heating Pad for the Brooder".
I wouldn't bother with any heat for adults, though. With proper acclimatization and well ventilated sleeping quarters, chickens survive in temps well below freezing. They have chickens in Alaska. Just go to the forum "Where are you?" and you'll find people raising chickens in thirty below without heat.
I use the oil-filled heaters in my coops, but I set them to the lowest setting just to keep it from freezing the poop to the poop boards, making it easier to clean in the mornings when it's in the single digits like this morning. If your climate is high in moisture, you would be risking frost bite by adding heat to the damp air. I know it sounds wacky, but those are the real risks of trying to heat coops unless you live in a very arid climate.
I recommend you save your money and just concentrate on proper ventilation and good diet and let your chickens acclimate to the cold.