You didn't tell us the breed, unless I missed it.
I brood mine out in the barn, as chick dust is unholy. It's like someone sawing drywall inside your house, as someone put it.
Of course, I brood under a heat lamp, but at 4 weeks, as they feather, I normally, find I can decrease the wattage, as they no longer like being that warm. They regulate themselves. Under the direct spot of the lamp, if they are cool, but more away if they are warm. I move them at 5-6 weeks into the pen in the barn. I leave a warming light on for them. Higher up and with the guard on. By 7 or 8 weeks, they are done with the lamp altogether. It's not me, so much, pulling the lamp away from them, as it is they not wanting that heat anymore.
The barn isn't insulated nor heated otherwise. Of course, it takes a while for chickens to gradually acclimate in fall to winter temps. I allow this to happen naturally. By dead of winter, they are fully acclimated and require no heat whatsoever. They've adjusted just fine. However, good ventilation is absolutely required.