15 or 16 weeks is absurd. New chicks need extra heat and protection til they are fully feathered, which is usually around 5 or 6 weeks. They can be outdoors from day one, if you are set up to brood chicks outdoors, as many of us are, often after going through brooding them indoors. The only...
Did you just put them in there? It may take several days before they consider it home. How much ventilation does it have, and how big is it? Is there outside air blowing on them, or on the roost?