Building a coop in WA (western) do we need insulation?

[spottedjagiwar]

I have a wide assortment of chicks. When we build the coop, should it be insulated? Temps have gotten as high as 100, and as low as 18, though both are fairly rare.

 

[15shenyl]

In our area of Washington I have seen days that it gets 103 and as low as 20. I don't have insulation, but we have trees and bushes with dirt under them so they can stay cool and in winter I put in heat lamps, they always come out unless theirs snow, they hate snow.