I don't know where you live, but do you need insulation? We had 4 days with temps -8 to 15, had no insulation, no heat source. All were fine. The 2 roos had a bit of frostbite but it appears gone. Often the nights (some days) are in the 20s.Oooo maybe I'll do that when I set them up in the garage might even enclose a specific area with a moving blanket to get the heat in one spot. It still gets down to the 20s sometimes. Supposed to rain and drop under 30 at night. Maybe I'll even get another light just to be extra until I get this coop built and insulated.
The chicks also need to be able to get away from the heat. Our 3 day old chicks were moving away from directly under the heat lamp. It was 95/96, so I adjusted and it is about 92 with other areas 80-85. Food and water are away from the warmest area.