I take it we are talking hatchery chicks.
Less than a month or so you need heat. As in 95F in the first week, 80-85 at 4-5 weeks. You cannot get around this. Just insulation is absolutely not going to cut it -- they are not generating and retaining enough heat on their own. They will die.
Seems to me the only solution short of a generator is a kerosene heater or similar. If the chicks have not yet arrived figure this all out ahead of time and make sure you can keep that temperature up -- use a thermometer that will show daily maximum and minimum so you know how low it gets at night. Of course mid-summer is the time to do this, but even then you will need heat.
In the future, if you can, consider letting hens do the work. They are far better at it than we are and your peeps will be stronger, happier and far smarter. I know.. it's not always realistic or possible but it is by far the best way.
Edit: I forgot to say this: if you think about the way a chick is raised by it's mom, the heat
should be like that, so that there is a place of direct, full-on high heat and areas of less heat. This allows them to self-regulate and is why heat lamps are so good.