Coming out of frigid Rhode Island this morning. 0 degrees with a feel like temp of -10. I agree with everyone about not using hay or straw. If you haven't had an impacted crop yet, consider yourself lucky! I use pellet stove pellets (wood pellets) in some of my lower breed cages, I don't wet them down, just put them in as they are. The droppings do break them down in time and when I feel they are no longer absorbent enough, I clean them out and add a new bag. My buildings are not insulated, but I do cover my runs with clear marine vinyl. It gets costly, BUT, it allows the sunshine in, warms up the run, is way more sturdy than the opaque plastic bought at box stores (I have used it in a pinch though!) and sometimes at the end of the season, I am able to re-use some of it for the next year. I just unstaple it, roll it up to the top and zip tie still attached. I'm not sure exactly how much warmer it makes things but I can say that it feels a heck of a lot warmer than outside. Hoping everyone's birds stay safe!!