Larry, you seem like the sort of fellow who likes to have all his ducks in a row before he begins a serious endeavor. I urge you to read Blooie's essay she wrote about brooding chicks outdoors. Then I urge you to commit to finishing the coop completely and then order your chicks even if it's still winter. When they arrive, install them right in the new coop with the heating pad system of brooding.
If you have time, read through Blooie's thread "Mama-heating pad in the Brooder". It's long, but chock full of people's experiences in utilizing this rather revolutionary method of brooding chicks. I was one of them.
There are many advantages to brooding outdoors in a chickens' natural environment, the least of which is saving your home and sanity the trials aggravation of chick dander, noise, smell, etc.
Chicks raised this way, out in the coop where they'll be living the rest of their lives, are more cold hardy, more self confident, more advanced in their various life stages and development, and are calmer and more easily handled.
Chicks raised in the highly confined and artificial environment of a brooder in the house are more dependent on heat, are more skittish and fearful when moved from the brooder confinement to the larger environment of the coop and run, and are more prone to suffering from problems associated with overcrowding.
I've raised two groups of chicks since spring outdoors right in my run under the heating pad system. It did not matter in the least what the temperatures were. Blooie had sub-freezing temps and her chicks did splendidly. My first group thrived under night temps in the 30s and day temps in the 50s. They were happy and ran all over the spacious run, ducking into their heating pad cave for brief warm-ups. The second group arrived in mid summer, and they were a breeze to raise, and they're seven weeks old right now. I'll never, ever raise chicks in a brooder in the house again.
The chicks will respond to cold temps by feathering out more quickly. They also are ready to roost at a much younger age than indoor chicks. They're self confident because they are being raised in one place without the disruption and trauma of needing to transition to the coop from a brooder box. And you have the advantage of having all the chicken mess confined to the coop and not your home.
You can finish the run at your leisure, and have it ready for the chicks to romp in come spring. Please give serious consideration to this alternative to brooding chicks indoors. I guarantee you will not be sorry.