My chicks are 3 weeks and 3 days and I was planning on moving them to the garage when they are 4 weeks with a heat lamp. When they are a month and half or fully feathered I was going to move them to the coop... should I use a heat lamp still at nights? I live in Iowa and the temperature is like a Roller Coaster! Nights can be anywhere from 50°-70° while the days are from 50°-90.. haven't quite reached 100° yet..any suggestions?