Do you have a coop and run yet? If so, why not just install the chicks outdoors where they will be living for the rest of their lives?
Last summer, I finally saw the ridiculousness of brooding in a box indoors when I had a wonderful, spacious and perfectly safe "brooder" already set up outside. I have a partitioned run with a couple of areas that can be closed off from the adults. Last summer I used the larger one, and yesterday, installed some new day-olds in the smaller enclosure.
This morning, the now two-day olds woke up to 39F, but they were snug and warm in their heating pad cave. As it warms up naturally by the sun, they will spend more time running around the spacious sand pen, ducking into the heating pad cave as they begin to lose body heat, warm up for a bit, then they will run out and play for much longer than one might expect before needing a quick warm up again. Yesterday, their first day after being hatched at the hatchery, it didn't get warmer than 70F, but the chicks were out running about more than they were under their heat source, proving how chicks do not need to be kept at a constant 95F.
If your chicks have been used to a heat lamp, no problem, just hang it in a corner of a pen and they will use it as they need it, spending the rest of their time doing important chick stuff in the luxurious space that no brooder box, no matter how large, will be able to equal.
For pics of my set up, see my article on outdoor brooding linked below this post.