Chicks will let you know when they are not comfortable. If cold, they gather close to the source of heat and cheep in a tremulous or shrill tone. If too hot, they will move away from the heat. When temperature is correct, they spread out evenly around the brooder. Chick talk is the key to comfort.
Ventilation is very important.
Do not close up your building tightly so that air cannot come in. Chicks need fresh air, but drafts must be avoided. Proper ventilation helps keep litter dry by removing excess moisture. Watering Water is the most important thing that you give your chicks. Chicks need about twice as much water by weight as feed.