My new coop has 1" of thermax in the ceiling, metal roof. No insulation in the sides or floor. But, it does have lots of glass: 3 thermopane 2 x 3 windows, and a full thermopane glass door (all wonderful gleanings from the town dump.) Windows and door are on south and east, so lots of good sun gain. Coop in 10 x 12, 2 x 4 perches. While insulation is not necessary, it does help keep the temps from wild swings. Helps the coop stay warmer in the winter: hold that solar gain, and helps it stay cooler in the summer: helps to prevent that roof from turning it into an oven in the summer. IMO, if you can afford it and want to, insulation is a good thing. If you don't want to, that's ok too. But, most importantly, good ventilation is a must. Bee Kissed is a strong advocate of having insulation at floor level in her deep litter West Virginia coop. She says it does a great job of catching any ammonia and drawing it up and out. I'm still planning the landscaping around my coop, and think I'll plant some deciduous trees on the east, and maybe the south, so they'll shade in the summer, but allow the sun in in the winter.