TAke out the heat lamp before you "cook" your chicks or burn down your coop (unless you have carefully placed a thermometer under the lamp and KNOW that the temp is not too high for them--or on the floor or sides of your coop)! 6 weeks olds need about 70 degrees f. for comfort, food and water easy reach and not under the lamp. (A 75W incandescant bulb may be more than enough heat). When well feathered, they can take quite a bit of "cold", but not the COLD of Montana. I have a radiator heater to keep my bantams above 30 degrees temp. Water is up high on a shelf, so doesn't freeze, but your Silkies cannot fly very high. It is zero to 10 above at my farm-- night and day, so too cold for my bantams outside--but plenty of room in their insulated house. Apples cut in half, give them something to scratch about and keep moving. Such dears, had a fairly mild fall and early winter, but now WINTER COLD is here--and will keep those bantams safe, not too warm, but not too cold! My rooster's combs can freeze at 27 degrees f. Good luck.....(used to hatch year around, but raised chicks in boxes in a spare bedroom and not outside houses until at least 2-2 1/2 months old. That is a dusty project, but didn't mind (I do, now. No chicks until April!)