I agree with ranch hand and ozark hen. I keep my brooder in our large bathroom, and start off with an 85 or 100 watt bulb, then raise the bulb and lower wattage as needed to maintain proper heat levels. I always use a red landscaping bulb (reduces pecking) the first few weeks.
It's such a hard thing to advise, each brooder situation is different. If you have the brooder in a warm location, you will need less added heat. Use your judgement and watch the chicks, they will spread out all over if warm enough.
Best of luck to you!