You need to read up on ventilation. That is the MOST important part. Insulation does not do as much if there is no heat added. Each chicken produces little heat to warm the coop. They fluff up and keep the heat to themselves. Drafts are the most important to eliminate.
Depending on the breed of your chicken,,, many will tolerate the cold OK. If you have chickens that are less cold-hardy, you may need to resort to some supplemental heat. I suggest only supplementing the minimum. If chickens are in too warm of a coop, then when they go outdoors, the temperature difference creates a shock. NO GOOD..
Post some pix of your coop, and some info on number and breed of chickens.
A HEAT LAMP, is something not very recommended.
This is a better/safer option.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,, and
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