And you might be interested in reading my article on brooding outdoors and how it has many more benefits than indoor brooding. I just finished brooding four chicks outdoors and they are feathered completely at just under five weeks and are now living in the coop.
The temps were in the 30s at night when I brought them home and installed them under their heating pad cave, and it was under 70F all day the first day when they were a whopping one day old. They spent very little time under the heat.
You aren't trying to "maintain" a temperature, but providing a heat source for the chicks to warm themselves as they lose body heat. They aren't meat that needs to be kept at a constant temp.
Click on the second link below this post.