Interesting feedback, everyone.
I have to say, that this is not theory, in my case, but is my actual experience, thus far.
Currently the house temp is 72 degrees, the brooder is
cool to the touch, the thermometer is reading exactly 95 degrees,
and is not at all warm to the touch, made of plastic. The other end of the brooder is cooler, at 85 degrees.
I've added a second thermometer, as I'm curious about this! I'll update when/if something changes.
IMO: the only thing that changed the temperature at all, was an opening door to outside, and then it dropped by 5 degrees. Resumed 95 degrees around 5-10 minutes later.
My brooder that I constucted, is a 40 gallon dark blue Rubbermaid bin with lid removed, btw. Don't know if that is conducting heat differently than others' brooders?
I certainly trust the more seasoned chick raisers' collective wisdom, and it's interesting how others have had success with the 250 watt bulb and then others haven't!