my chicks are out from day l ... leave one side of brooder open at all times. (for open air - wired ).(use tarp when windy, rainy or just nasty out ) .. use 2 heat lamps (had 26 chicks) nailed securely so no fires.. room for them to move away when warm and move under when cold....they are now 2 months and have moved to their own BIG GIRL coop with dirt floor...added straw to keep them off dirt in very cold weather (28 degrees as of late) they sleep in a bunch for warmth ... all is well...they are all feathered out and don't seem to be bothered by the cold at all....much less work now that they are out of brooder... NO HEAT needed after 6 weeks should have all their feathers by then....they need to aclimate to the cold ..use heat lamp only until they get all their feathers or EXTREME cold....better for their health....This is what I learned on BYC and has proven correct....growing, growing, growing,.. best of luck - G Merry Christmas