They want to be outside, pecking and scratching, with plenty of room for this. They will peck each other when deprived. At 5 weeks they may very well be feathered enough to go outside without heat, especially if they are already spending the day outdoors, depending where you live. They certainly don't need any added heat at this age if they are still indoors, and if the weather is not awful, they will do much better if they have at least some outdoor time every day..