Hello new chick mom/dad! What zone are you in? I am in zone 5 and our weather is unpredictable, tonight it will be getting down to 35. We put ours out in the coop at 5/4 weeks, however there is 52 babies that were a week apart and 44 big girls plus our coop is insulated. We put a heat lamp on a stationary pole and then clamped it for double security! Heat lamps can cause a fire if it were to fall so they must be secure. Some people wait longer to put there chicks out and that is ok - alot will depend on what your set-up is. If you only have 12 I would probably wait a few more weeks.

Unless all danger of frost is over with you can not go wrong with a little supplemental heat until they are about 8 weeks old. first year my girls will have a little supplemental heat being this is their first winter but next year? forgedda-bout-it. Mines were put in the pen at 4 weeks I think and they should be going on 8 weeks now. I will take the lamp off them 100% when every night is a comfortable night and like I said next year no supplements light. I have a smaller box inside the pen that they huddled up together and hardly any squawking.