I double the Warm & and it's good and warm and if you use flannel for the backing it feels snuggly.

I recently made a tied quilt with two layers of corduroy, no batting. Heavy as all get out! But very warm.
I'm also part way done with three other hand quilted lap/throw quilts that have pieced top and fleece backing. They are much lighter weight, but also quite warm.

Actually, poly is the warmest batting since it does not breathe. Put minkee as the backing and she will be toasty!

Wool.... There is nothing like wool!

Wool?

Oh, do a good wool batting if at all possible. My fave brand is Dream Wool. Love the stuff, it quilts really tiny stitches and is soft, light weight and warm in winter and cool in summer, a miracle fiber. By the by, it is machine washable.

Wool is an absolute dream to hand quilt. I only use it for special quilts for special people, but it's wonderful.

Thanks everyone for your input to my question. For you longarm quilters, do you have any problems with quilting when you use fleece for the batting with regular cotton fabric for the backing?

Fleece is very warm and solids go on sale often or use a 40% off from JoAnn's. Wool is very warm too. I use bamboo but I live in Florida so I'm not sure where it fits on the warmth scale.

I've always heard that wool is best for warmth.